* Re: [PATCH 02/20] t: add library for munging chunk-format files
From: Taylor Blau @ 2023-10-10 23:47 UTC (permalink / raw)
To: Jeff King; +Cc: git
In-Reply-To: <20231009205838.GB3282181@coredump.intra.peff.net>
On Mon, Oct 09, 2023 at 04:58:38PM -0400, Jeff King wrote:
> ---
> t/lib-chunk.sh | 17 ++++++++
> t/lib-chunk/corrupt-chunk-file.pl | 66 +++++++++++++++++++++++++++++++
> 2 files changed, 83 insertions(+)
> create mode 100644 t/lib-chunk.sh
> create mode 100644 t/lib-chunk/corrupt-chunk-file.pl
I can't claim to be a competent reviewer for the Perl portions of this
patch. But I agree with the goal and am glad to see us getting away from
the brittle implementation that we have been living with in the test
suite.
Thanks,
Taylor
^ permalink raw reply
* Re: [PATCH 01/20] chunk-format: note that pair_chunk() is unsafe
From: Taylor Blau @ 2023-10-10 23:45 UTC (permalink / raw)
To: Jeff King; +Cc: git
In-Reply-To: <20231009205823.GA3282181@coredump.intra.peff.net>
On Mon, Oct 09, 2023 at 04:58:23PM -0400, Jeff King wrote:
> There are no callers of the "safe" version yet, but we'll add some in
> subsequent patches.
Makes sense.
> +int pair_chunk_unsafe(struct chunkfile *cf,
> + uint32_t chunk_id,
> + const unsigned char **p)
> {
> - return read_chunk(cf, chunk_id, pair_chunk_fn, p);
> + size_t dummy;
> + return pair_chunk(cf, chunk_id, p, &dummy);
I have always disliked functions that require you to pass a non-NULL
pointer to some value that you may or may not want to have that function
fill out. So I was going to suggest something along the lines of
"pair_chunk() should tolerate a NULL fourth argument instead of filling
out the size unconditionally".
But that's (a) the whole point of the series ;-), and (b) unnecessary,
since this function is going to go away entirely by the end of the
series, too.
So I think that the call you made here was the right one. The rest of
the patch all looks good to me, let's read on...
Thanks,
Taylor
^ permalink raw reply
* Re: [PATCH 1/1] [OUTREACHY] Fixed add.c file to conform to guidelines when using die() listed in issue #635
From: Junio C Hamano @ 2023-10-10 22:24 UTC (permalink / raw)
To: Naomi Ibe; +Cc: git
In-Reply-To: <CACS=G2yUGGJwD05KOFZK+AV3TSNDvDEfC=pFRsLwKX_-dgt+gA@mail.gmail.com>
Naomi Ibe <naomi.ibeh69@gmail.com> writes:
> Thank you very much! I'd definitely make those changes on my next patch.
[administrivia] do not top post.
> Should I begin work on version 2 or should I still wait for additional
> input on the version 1?
There is no "rule", but based on observations on how people behave,
e.g.
* for a small patch like this that can be given a good review in 10
minutes or so, those who do not do so within the first 3 days
will probably not do so.
* once a reasonably thorough review is given, those who haven't
responded to the patch and do not have much else to say are
unlikely to respond.
* on the other hand, after such a review is given, those who do not
agree with the review tend to respond rather quickly, to get
their voice in before it becomes too late.
I would say it would be good to start working on it right away and
use a couple of days reviewing it yourself before posting it.
^ permalink raw reply
* Re: [PATCH v3 2/2] attr: add attr.tree for setting the treeish to read attributes from
From: Junio C Hamano @ 2023-10-10 22:14 UTC (permalink / raw)
To: John Cai via GitGitGadget; +Cc: git, Jeff King, Jonathan Tan, John Cai
In-Reply-To: <dadb822da99772cd277417f564cf672f65d1cc24.1696967380.git.gitgitgadget@gmail.com>
"John Cai via GitGitGadget" <gitgitgadget@gmail.com> writes:
> From: John Cai <johncai86@gmail.com>
>
> 44451a2 (attr: teach "--attr-source=<tree>" global option to "git",
> 2023-05-06) provided the ability to pass in a treeish as the attr
> source. In the context of serving Git repositories as bare repos like we
> do at GitLab however, it would be easier to point --attr-source to HEAD
> for all commands by setting it once.
>
> Add a new config attr.tree that allows this.
>
> Signed-off-by: John Cai <johncai86@gmail.com>
> ---
> Documentation/config.txt | 2 ++
> Documentation/config/attr.txt | 5 +++
> attr.c | 7 ++++
> attr.h | 2 ++
> config.c | 14 ++++++++
> t/t0003-attributes.sh | 62 +++++++++++++++++++++++++++++++++++
> 6 files changed, 92 insertions(+)
> create mode 100644 Documentation/config/attr.txt
>
> diff --git a/Documentation/config.txt b/Documentation/config.txt
> index 229b63a454c..b1891c2b5af 100644
> --- a/Documentation/config.txt
> +++ b/Documentation/config.txt
> @@ -371,6 +371,8 @@ other popular tools, and describe them in your documentation.
>
> include::config/advice.txt[]
>
> +include::config/attr.txt[]
> +
> include::config/core.txt[]
>
> include::config/add.txt[]
> diff --git a/Documentation/config/attr.txt b/Documentation/config/attr.txt
> new file mode 100644
> index 00000000000..be882523f8b
> --- /dev/null
> +++ b/Documentation/config/attr.txt
> @@ -0,0 +1,5 @@
> +attr.tree:
> + A <tree-ish> to read gitattributes from instead of the worktree. See
> + linkgit:gitattributes[5]. If `attr.tree` does not resolve to a valid tree,
> + treat it as an empty tree. --attr-source and GIT_ATTR_SOURCE take
> + precedence over attr.tree.
Properly typeset `--attr-source` and `GIT_ATTR_SOURCE`.
A quick "git grep" in Documentation/config/*.txt tells me that
nobody refers to an object type like <tree-ish>. Imitate what this
was modeled after, namely Documentation/config/mailmap.txt, which
says just
... a reference to a blob in the repository.
without any half mark-up.
More importantly, the description makes one wonder what the
precedence rule between these two (the general rule would be for
command line parameter to override environment, if I recall
correctly).
I think the enumeration header usually is followed by double-colons
among Documentation/config/*.txt files. Let's be consistent.
In the context of this expression, "worktree" is a wrong noun to
use---the term of art refers to an instance of "working tree",
together with some "per worktree" administrative files inside .git/
directory. On the other hand, "working tree" refers to the "files
meant to be visible to build tools and editors part of the non-bare
repository", which is what you want to use here.
attr.tree::
A tree object to read the attributes from, instead of the
`.gitattributes` file in the working tree. In a bare
repository, this defaults to HEAD:.gitattributes". If a
given value does not resolve to a valid tree object, an
empty tree is used instead. When `GIT_ATTR_SOURCE`
environment variable or `--attr-source` command line option
is used, this configuration variable has no effect.
or something along that line, perhaps.
> diff --git a/attr.c b/attr.c
> index bf2ea1626a6..0ae6852d12b 100644
> --- a/attr.c
> +++ b/attr.c
> @@ -24,6 +24,8 @@
> #include "tree-walk.h"
> #include "object-name.h"
>
> +const char *git_attr_tree;
> +
> const char git_attr__true[] = "(builtin)true";
> const char git_attr__false[] = "\0(builtin)false";
> static const char git_attr__unknown[] = "(builtin)unknown";
> @@ -1206,6 +1208,11 @@ static void compute_default_attr_source(struct object_id *attr_source)
> if (!default_attr_source_tree_object_name)
> default_attr_source_tree_object_name = getenv(GIT_ATTR_SOURCE_ENVIRONMENT);
>
> + if (!default_attr_source_tree_object_name) {
> + default_attr_source_tree_object_name = git_attr_tree;
> + ignore_bad_attr_tree = 1;
> + }
As long as "attr.tree" was read by calling git_default_attr_config()
before we come here, git_attr_tree is not NULL and we allow bad attr
tree in default_attr_source_tree_object_name. But stepping back a
bit, even if "attr.tree" is unspecified, i.e., git_attr_tree is
NULL, we set ignore_bad_attr_tree to true here.
What it means is that after the above if() statement, if
default_attr_source_tree_object_name is still NULL, we know that
ignore_bad_attr_tree is already set to true.
> if (!default_attr_source_tree_object_name &&
> startup_info->have_repository &&
> is_bare_repository()) {
So would it make more sense to remove the assignment to the same
variable we made in [1/2] around here (not seen in the post
context)?
Alternatively, even though it makes the code a bit more verbose, the
logic might become clearer if you wrote the "assign from the config"
part like so:
if (!default_attr_source_tree_object_name && git_attr_tree) {
default_attr_source_tree_object_name = git_attr_tree;
ignore_bad_attr_tree = 1;
}
It would leave more flexibility to the code around here. You could
for example add code that assigns a different value, a tree object
that is required to exist, to default_attr_source_tree_object_name
after this point, for example, without having to wonder what the
"current" value of ignore_bad_attr_tree is.
> +static int git_default_attr_config(const char *var, const char *value)
> +{
> + if (!strcmp(var, "attr.tree"))
> + return git_config_string(&git_attr_tree, var, value);
> +
> + /* Add other attribute related config variables here and to
> + Documentation/config/attr.txt. */
/*
* Our multi-line comments should look
* more like this; opening slash-asterisk
* and closing asterisk-slash sit on a line
* on its own.
*/
> @@ -342,6 +346,46 @@ test_expect_success 'bare repository: check that .gitattribute is ignored' '
> )
> '
>
> +bad_attr_source_err="fatal: bad --attr-source or GIT_ATTR_SOURCE"
Not a fault of this two-patch series, but we probably should refine
this error reporting so that the reader can tell which one is being
complained about, and optionally what the offending value was.
> +test_expect_success 'attr.tree when HEAD is unborn' '
> + test_when_finished rm -rf empty &&
> + git init empty &&
> + (
> + cd empty &&
> + echo $bad_attr_source_err >expect_err &&
Let's not rely on words in the error message split with exactly one
whitespace each and instead quote the variable properly. I.e.,
echo "$bad_attr_source_err" >expect_err &&
But this is not even used, as we do not expect it to fail. Perhaps
remove it altogether?
> + echo "f/path: test: unspecified" >expect &&
> + git -c attr.tree=HEAD check-attr test -- f/path >actual 2>err &&
> + test_must_be_empty err &&
> + test_cmp expect actual
> + )
> +'
> +
> +test_expect_success 'attr.tree points to non-existing ref' '
> + test_when_finished rm -rf empty &&
> + git init empty &&
> + (
> + cd empty &&
> + echo $bad_attr_source_err >expect_err &&
Ditto.
> + echo "f/path: test: unspecified" >expect &&
> + git -c attr.tree=refs/does/not/exist check-attr test -- f/path >actual 2>err &&
> + test_must_be_empty err &&
> + test_cmp expect actual
> + )
> +'
> +
> +test_expect_success 'bad attr source defaults to reading .gitattributes file' '
> + test_when_finished rm -rf empty &&
> + git init empty &&
> + (
> + cd empty &&
> + echo "f/path test=val" >.gitattributes &&
> + echo "f/path: test: val" >expect &&
> + git -c attr.tree=HEAD check-attr test -- f/path >actual 2>err &&
> + test_must_be_empty err &&
> + test_cmp expect actual
> + )
> +'
In other words, with the additional tests, we do not check error
cases (which may be perfectly OK, if they are covered by existing
tests). A bit curious.
> @@ -356,6 +400,24 @@ test_expect_success 'bare repo defaults to reading .gitattributes from HEAD' '
> test_cmp expect actual
> '
>
> +test_expect_success '--attr-source and GIT_ATTR_SOURCE take precedence over attr.tree' '
Do we want to ensure which one takes precedence between the command
line option and the environment? It's not like the one that is
given the last takes effect.
> + test_when_finished rm -rf empty &&
> + git init empty &&
> + (
> + cd empty &&
> + git checkout -b attr-source &&
> + test_commit "val1" .gitattributes "f/path test=val1" &&
> + git checkout -b attr-tree &&
> + test_commit "val2" .gitattributes "f/path test=val2" &&
> + git checkout attr-source &&
> + echo "f/path: test: val1" >expect &&
> + git -c attr.tree=attr-tree --attr-source=attr-source check-attr test -- f/path >actual &&
> + test_cmp expect actual &&
> + GIT_ATTR_SOURCE=attr-source git -c attr.tree=attr-tree check-attr test -- f/path >actual &&
> + test_cmp expect actual
> + )
> +'
> +
> test_expect_success 'bare repository: with --source' '
> (
> cd bare.git &&
Other than that, looking great. Thanks.
^ permalink raw reply
* Re: [PATCH v4 4/4] parse: separate out parsing functions from config.h
From: Junio C Hamano @ 2023-10-10 20:57 UTC (permalink / raw)
To: Phillip Wood; +Cc: Jonathan Tan, git, Calvin Wan
In-Reply-To: <87c16c09-784f-4818-9231-8023fc2c5a02@gmail.com>
Phillip Wood <phillip.wood123@gmail.com> writes:
>> I'm open to changing
>> git_config_get_expiry_date_in_days() too, though...we probably don't
>> need so many days.
>
> Indeed, the existing code passes maximum_signed_value_of_type(int) as
> the third argument to limit it to INT_MAX already.
Yeah, in other words, the current implementation does not allow us
to express the days more than an int can, so it is no brainer to
switch to use git_parse_int(). Allowing longer expiration period
is obviously outside the scope of this series.
Thanks.
^ permalink raw reply
* Re: What's cooking in git.git (Oct 2023, #03; Fri, 6)
From: Taylor Blau @ 2023-10-10 20:36 UTC (permalink / raw)
To: Junio C Hamano; +Cc: git
In-Reply-To: <xmqqh6n24zf1.fsf@gitster.g>
On Sat, Oct 07, 2023 at 01:20:02AM -0700, Junio C Hamano wrote:
> * tb/path-filter-fix (2023-08-30) 15 commits
> - bloom: introduce `deinit_bloom_filters()`
> - commit-graph: reuse existing Bloom filters where possible
> - object.h: fix mis-aligned flag bits table
> - commit-graph: drop unnecessary `graph_read_bloom_data_context`
> - commit-graph.c: unconditionally load Bloom filters
> - t/t4216-log-bloom.sh: harden `test_bloom_filters_not_used()`
> - bloom: prepare to discard incompatible Bloom filters
> - bloom: annotate filters with hash version
> - commit-graph: new filter ver. that fixes murmur3
> - repo-settings: introduce commitgraph.changedPathsVersion
> - t4216: test changed path filters with high bit paths
> - t/helper/test-read-graph: implement `bloom-filters` mode
> - bloom.h: make `load_bloom_filter_from_graph()` public
> - t/helper/test-read-graph.c: extract `dump_graph_info()`
> - gitformat-commit-graph: describe version 2 of BDAT
>
> The Bloom filter used for path limited history traversal was broken
> on systems whose "char" is unsigned; update the implementation and
> bump the format version to 2.
>
> What's the status of this thing?
> cf. <20230830200218.GA5147@szeder.dev>
> cf. <20230901205616.3572722-1-jonathantanmy@google.com>
> cf. <20230924195900.GA1156862@szeder.dev>
> source: <cover.1693413637.git.jonathantanmy@google.com>
Good question ;-). There were a couple of outstanding issues pointed out
by SZEDER Gábor that I addressed on top of what's already there.
I tied up what I think are all of the remaining loose ends and put
everything together in a single unified (if a little long) patch series.
This should be ready to go, but I'd love to hear from Jonathan Tan and
SZEDER before declaring victory here.
Thanks,
Taylor
^ permalink raw reply
* Re: [PATCH 07/15] commit-graph: new filter ver. that fixes murmur3
From: Taylor Blau @ 2023-10-10 20:34 UTC (permalink / raw)
To: Junio C Hamano; +Cc: SZEDER Gábor, Jonathan Tan, git, Jeff King
In-Reply-To: <xmqqr0m3y3o2.fsf@gitster.g>
On Mon, Oct 09, 2023 at 12:52:13PM -0700, Junio C Hamano wrote:
> Taylor Blau <me@ttaylorr.com> writes:
>
> > However, I am not entirely sure I agree with you that this is a "new"
> > issue. At least in the sense that Git (on 'master') does not currently
> > know how to deal with Bloom filters that have different settings across
> > commit-graph layers.
> >
> > IOW, you could produce this problem today using the test you wrote in
> > <20201015132147.GB24954@szeder.dev> using different values of the
> > GIT_BLOOM_SETTINGS environment variables as a proxy for different values
> > of the commitGraph.changedPathsVersion configuration variable introduced
> > in this series.
> >
> > So I think that this series makes it easier to fall into that trap, but
> > the trap itself is not new. I think a reasonable stopgap (which IIUC you
> > have suggested earlier) is to prevent writing a new commit-graph layer
> > with a different hash version than the previous layer.
>
> What we probably want more urgently than that stopgap is to perhaps
> teach the code pretend as if commit-graph did not exist when we
> detect multiple layers use different hash versions (or perhaps only
> use the base layer and ignore the rest as an anti-pessimization), to
> protect correctness first, no?
Very good suggestion, thanks.
Thanks,
Taylor
^ permalink raw reply
* [PATCH v3 17/17] bloom: introduce `deinit_bloom_filters()`
From: Taylor Blau @ 2023-10-10 20:34 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
After we are done using Bloom filters, we do not currently clean up any
memory allocated by the commit slab used to store those filters in the
first place.
Besides the bloom_filter structures themselves, there is mostly nothing
to free() in the first place, since in the read-only path all Bloom
filter's `data` members point to a memory mapped region in the
commit-graph file itself.
But when generating Bloom filters from scratch (or initializing
truncated filters) we allocate additional memory to store the filter's
data.
Keep track of when we need to free() this additional chunk of memory by
using an extra pointer `to_free`. Most of the time this will be NULL
(indicating that we are representing an existing Bloom filter stored in
a memory mapped region). When it is non-NULL, free it before discarding
the Bloom filters slab.
Suggested-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
bloom.c | 16 +++++++++++++++-
bloom.h | 3 +++
commit-graph.c | 4 ++++
3 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/bloom.c b/bloom.c
index 24dd874e46..ff131893cd 100644
--- a/bloom.c
+++ b/bloom.c
@@ -59,6 +59,7 @@ int load_bloom_filter_from_graph(struct commit_graph *g,
sizeof(unsigned char) * start_index +
BLOOMDATA_CHUNK_HEADER_SIZE);
filter->version = g->bloom_filter_settings->hash_version;
+ filter->to_free = NULL;
return 1;
}
@@ -231,6 +232,18 @@ void init_bloom_filters(void)
init_bloom_filter_slab(&bloom_filters);
}
+static void free_one_bloom_filter(struct bloom_filter *filter)
+{
+ if (!filter)
+ return;
+ free(filter->to_free);
+}
+
+void deinit_bloom_filters(void)
+{
+ deep_clear_bloom_filter_slab(&bloom_filters, free_one_bloom_filter);
+}
+
static int pathmap_cmp(const void *hashmap_cmp_fn_data UNUSED,
const struct hashmap_entry *eptr,
const struct hashmap_entry *entry_or_key,
@@ -247,7 +260,7 @@ static int pathmap_cmp(const void *hashmap_cmp_fn_data UNUSED,
static void init_truncated_large_filter(struct bloom_filter *filter,
int version)
{
- filter->data = xmalloc(1);
+ filter->data = filter->to_free = xmalloc(1);
filter->data[0] = 0xFF;
filter->len = 1;
filter->version = version;
@@ -449,6 +462,7 @@ struct bloom_filter *get_or_compute_bloom_filter(struct repository *r,
filter->len = 1;
}
CALLOC_ARRAY(filter->data, filter->len);
+ filter->to_free = filter->data;
hashmap_for_each_entry(&pathmap, &iter, e, entry) {
struct bloom_key key;
diff --git a/bloom.h b/bloom.h
index e3a9b68905..d20e64bfbb 100644
--- a/bloom.h
+++ b/bloom.h
@@ -56,6 +56,8 @@ struct bloom_filter {
unsigned char *data;
size_t len;
int version;
+
+ void *to_free;
};
/*
@@ -96,6 +98,7 @@ void add_key_to_filter(const struct bloom_key *key,
const struct bloom_filter_settings *settings);
void init_bloom_filters(void);
+void deinit_bloom_filters(void);
enum bloom_filter_computed {
BLOOM_NOT_COMPUTED = (1 << 0),
diff --git a/commit-graph.c b/commit-graph.c
index 571f38335a..7ccec429cb 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -787,6 +787,7 @@ static void close_commit_graph_one(struct commit_graph *g)
void close_commit_graph(struct raw_object_store *o)
{
close_commit_graph_one(o->commit_graph);
+ deinit_bloom_filters();
o->commit_graph = NULL;
}
@@ -2588,6 +2589,9 @@ int write_commit_graph(struct object_directory *odb,
res = write_commit_graph_file(ctx);
+ if (ctx->changed_paths)
+ deinit_bloom_filters();
+
if (ctx->split)
mark_commit_graphs(ctx);
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 16/17] commit-graph: reuse existing Bloom filters where possible
From: Taylor Blau @ 2023-10-10 20:34 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
In 9e4df4da07 (commit-graph: new filter ver. that fixes murmur3,
2023-08-01), a bug was described where it's possible for Git to produce
non-murmur3 hashes when the platform's "char" type is signed, and there
are paths with characters whose highest bit is set (i.e. all characters
>= 0x80).
That patch allows the caller to control which version of Bloom filters
are read and written. However, even on platforms with a signed "char"
type, it is possible to reuse existing Bloom filters if and only if
there are no changed paths in any commit's first parent tree-diff whose
characters have their highest bit set.
When this is the case, we can reuse the existing filter without having
to compute a new one. This is done by marking trees which are known to
have (or not have) any such paths. When a commit's root tree is verified
to not have any such paths, we mark it as such and declare that the
commit's Bloom filter is reusable.
Note that this heuristic only goes in one direction. If neither a commit
nor its first parent have any paths in their trees with non-ASCII
characters, then we know for certain that a path with non-ASCII
characters will not appear in a tree-diff against that commit's first
parent. The reverse isn't necessarily true: just because the tree-diff
doesn't contain any such paths does not imply that no such paths exist
in either tree.
So we end up recomputing some Bloom filters that we don't strictly have
to (i.e. their bits are the same no matter which version of murmur3 we
use). But culling these out is impossible, since we'd have to perform
the full tree-diff, which is the same effort as computing the Bloom
filter from scratch.
But because we can cache our results in each tree's flag bits, we can
often avoid recomputing many filters, thereby reducing the time it takes
to run
$ git commit-graph write --changed-paths --reachable
when upgrading from v1 to v2 Bloom filters.
To benchmark this, let's generate a commit-graph in linux.git with v1
changed-paths in generation order[^1]:
$ git clone git@github.com:torvalds/linux.git
$ cd linux
$ git commit-graph write --reachable --changed-paths
$ graph=".git/objects/info/commit-graph"
$ mv $graph{,.bak}
Then let's time how long it takes to go from v1 to v2 filters (with and
without the upgrade path enabled), resetting the state of the
commit-graph each time:
$ git config commitGraph.changedPathsVersion 2
$ hyperfine -p 'cp -f $graph.bak $graph' -L v 0,1 \
'GIT_TEST_UPGRADE_BLOOM_FILTERS={v} git.compile commit-graph write --reachable --changed-paths'
On linux.git (where there aren't any non-ASCII paths), the timings
indicate that this patch represents a speed-up over recomputing all
Bloom filters from scratch:
Benchmark 1: GIT_TEST_UPGRADE_BLOOM_FILTERS=0 git.compile commit-graph write --reachable --changed-paths
Time (mean ± σ): 124.873 s ± 0.316 s [User: 124.081 s, System: 0.643 s]
Range (min … max): 124.621 s … 125.227 s 3 runs
Benchmark 2: GIT_TEST_UPGRADE_BLOOM_FILTERS=1 git.compile commit-graph write --reachable --changed-paths
Time (mean ± σ): 79.271 s ± 0.163 s [User: 74.611 s, System: 4.521 s]
Range (min … max): 79.112 s … 79.437 s 3 runs
Summary
'GIT_TEST_UPGRADE_BLOOM_FILTERS=1 git.compile commit-graph write --reachable --changed-paths' ran
1.58 ± 0.01 times faster than 'GIT_TEST_UPGRADE_BLOOM_FILTERS=0 git.compile commit-graph write --reachable --changed-paths'
On git.git, we do have some non-ASCII paths, giving us a more modest
improvement from 4.163 seconds to 3.348 seconds, for a 1.24x speed-up.
On my machine, the stats for git.git are:
- 8,285 Bloom filters computed from scratch
- 10 Bloom filters generated as empty
- 4 Bloom filters generated as truncated due to too many changed paths
- 65,114 Bloom filters were reused when transitioning from v1 to v2.
[^1]: Note that this is is important, since `--stdin-packs` or
`--stdin-commits` orders commits in the commit-graph by their pack
position (with `--stdin-packs`) or in the raw input (with
`--stdin-commits`).
Since we compute Bloom filters in the same order that commits appear
in the graph, we must see a commit's (first) parent before we process
the commit itself. This is only guaranteed to happen when sorting
commits by their generation number.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
bloom.c | 90 ++++++++++++++++++++++++++++++++++++++++++--
bloom.h | 1 +
commit-graph.c | 5 +++
object.h | 1 +
t/t4216-log-bloom.sh | 35 ++++++++++++++++-
5 files changed, 127 insertions(+), 5 deletions(-)
diff --git a/bloom.c b/bloom.c
index 739fa093ba..24dd874e46 100644
--- a/bloom.c
+++ b/bloom.c
@@ -7,6 +7,9 @@
#include "commit-graph.h"
#include "commit.h"
#include "commit-slab.h"
+#include "tree.h"
+#include "tree-walk.h"
+#include "config.h"
define_commit_slab(bloom_filter_slab, struct bloom_filter);
@@ -250,6 +253,73 @@ static void init_truncated_large_filter(struct bloom_filter *filter,
filter->version = version;
}
+#define VISITED (1u<<21)
+#define HIGH_BITS (1u<<22)
+
+static int has_entries_with_high_bit(struct repository *r, struct tree *t)
+{
+ if (parse_tree(t))
+ return 1;
+
+ if (!(t->object.flags & VISITED)) {
+ struct tree_desc desc;
+ struct name_entry entry;
+
+ init_tree_desc(&desc, t->buffer, t->size);
+ while (tree_entry(&desc, &entry)) {
+ size_t i;
+ for (i = 0; i < entry.pathlen; i++) {
+ if (entry.path[i] & 0x80) {
+ t->object.flags |= HIGH_BITS;
+ goto done;
+ }
+ }
+
+ if (S_ISDIR(entry.mode)) {
+ struct tree *sub = lookup_tree(r, &entry.oid);
+ if (sub && has_entries_with_high_bit(r, sub)) {
+ t->object.flags |= HIGH_BITS;
+ goto done;
+ }
+ }
+
+ }
+
+done:
+ t->object.flags |= VISITED;
+ }
+
+ return !!(t->object.flags & HIGH_BITS);
+}
+
+static int commit_tree_has_high_bit_paths(struct repository *r,
+ struct commit *c)
+{
+ struct tree *t;
+ if (repo_parse_commit(r, c))
+ return 1;
+ t = repo_get_commit_tree(r, c);
+ if (!t)
+ return 1;
+ return has_entries_with_high_bit(r, t);
+}
+
+static struct bloom_filter *upgrade_filter(struct repository *r, struct commit *c,
+ struct bloom_filter *filter,
+ int hash_version)
+{
+ struct commit_list *p = c->parents;
+ if (commit_tree_has_high_bit_paths(r, c))
+ return NULL;
+
+ if (p && commit_tree_has_high_bit_paths(r, p->item))
+ return NULL;
+
+ filter->version = hash_version;
+
+ return filter;
+}
+
struct bloom_filter *get_bloom_filter(struct repository *r, struct commit *c)
{
struct bloom_filter *filter;
@@ -292,9 +362,23 @@ struct bloom_filter *get_or_compute_bloom_filter(struct repository *r,
filter, graph_pos);
}
- if ((filter->data && filter->len) &&
- (!settings || settings->hash_version == filter->version))
- return filter;
+ if (filter->data && filter->len) {
+ struct bloom_filter *upgrade;
+ if (!settings || settings->hash_version == filter->version)
+ return filter;
+
+ /* version mismatch, see if we can upgrade */
+ if (compute_if_not_present &&
+ git_env_bool("GIT_TEST_UPGRADE_BLOOM_FILTERS", 1)) {
+ upgrade = upgrade_filter(r, c, filter,
+ settings->hash_version);
+ if (upgrade) {
+ if (computed)
+ *computed |= BLOOM_UPGRADED;
+ return upgrade;
+ }
+ }
+ }
if (!compute_if_not_present)
return NULL;
diff --git a/bloom.h b/bloom.h
index bfe389e29c..e3a9b68905 100644
--- a/bloom.h
+++ b/bloom.h
@@ -102,6 +102,7 @@ enum bloom_filter_computed {
BLOOM_COMPUTED = (1 << 1),
BLOOM_TRUNC_LARGE = (1 << 2),
BLOOM_TRUNC_EMPTY = (1 << 3),
+ BLOOM_UPGRADED = (1 << 4),
};
struct bloom_filter *get_or_compute_bloom_filter(struct repository *r,
diff --git a/commit-graph.c b/commit-graph.c
index e0fc62e110..571f38335a 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1109,6 +1109,7 @@ struct write_commit_graph_context {
int count_bloom_filter_not_computed;
int count_bloom_filter_trunc_empty;
int count_bloom_filter_trunc_large;
+ int count_bloom_filter_upgraded;
};
static int write_graph_chunk_fanout(struct hashfile *f,
@@ -1716,6 +1717,8 @@ static void trace2_bloom_filter_write_statistics(struct write_commit_graph_conte
ctx->count_bloom_filter_trunc_empty);
trace2_data_intmax("commit-graph", ctx->r, "filter-trunc-large",
ctx->count_bloom_filter_trunc_large);
+ trace2_data_intmax("commit-graph", ctx->r, "filter-upgraded",
+ ctx->count_bloom_filter_upgraded);
}
static void compute_bloom_filters(struct write_commit_graph_context *ctx)
@@ -1757,6 +1760,8 @@ static void compute_bloom_filters(struct write_commit_graph_context *ctx)
ctx->count_bloom_filter_trunc_empty++;
if (computed & BLOOM_TRUNC_LARGE)
ctx->count_bloom_filter_trunc_large++;
+ } else if (computed & BLOOM_UPGRADED) {
+ ctx->count_bloom_filter_upgraded++;
} else if (computed & BLOOM_NOT_COMPUTED)
ctx->count_bloom_filter_not_computed++;
ctx->total_bloom_filter_data_size += filter
diff --git a/object.h b/object.h
index db25714b4e..2e5e08725f 100644
--- a/object.h
+++ b/object.h
@@ -75,6 +75,7 @@ void object_array_init(struct object_array *array);
* commit-reach.c: 16-----19
* sha1-name.c: 20
* list-objects-filter.c: 21
+ * bloom.c: 2122
* builtin/fsck.c: 0--3
* builtin/gc.c: 0
* builtin/index-pack.c: 2021
diff --git a/t/t4216-log-bloom.sh b/t/t4216-log-bloom.sh
index 8f8b5d4966..a321d8d713 100755
--- a/t/t4216-log-bloom.sh
+++ b/t/t4216-log-bloom.sh
@@ -221,6 +221,10 @@ test_filter_trunc_large () {
grep "\"key\":\"filter-trunc-large\",\"value\":\"$1\"" $2
}
+test_filter_upgraded () {
+ grep "\"key\":\"filter-upgraded\",\"value\":\"$1\"" $2
+}
+
test_expect_success 'correctly report changes over limit' '
git init limits &&
(
@@ -629,10 +633,19 @@ test_expect_success 'when writing another commit graph, preserve existing versio
test_expect_success 'when writing commit graph, do not reuse changed-path of another version' '
git init doublewrite &&
test_commit -C doublewrite c "$CENT" &&
+
git -C doublewrite config --add commitgraph.changedPathsVersion 1 &&
- git -C doublewrite commit-graph write --reachable --changed-paths &&
+ GIT_TRACE2_EVENT="$(pwd)/trace2.txt" \
+ git -C doublewrite commit-graph write --reachable --changed-paths &&
+ test_filter_computed 1 trace2.txt &&
+ test_filter_upgraded 0 trace2.txt &&
+
git -C doublewrite config --add commitgraph.changedPathsVersion 2 &&
- git -C doublewrite commit-graph write --reachable --changed-paths &&
+ GIT_TRACE2_EVENT="$(pwd)/trace2.txt" \
+ git -C doublewrite commit-graph write --reachable --changed-paths &&
+ test_filter_computed 1 trace2.txt &&
+ test_filter_upgraded 0 trace2.txt &&
+
(
cd doublewrite &&
echo "c01f" >expect &&
@@ -641,4 +654,22 @@ test_expect_success 'when writing commit graph, do not reuse changed-path of ano
)
'
+test_expect_success 'when writing commit graph, reuse changed-path of another version where possible' '
+ git init upgrade &&
+
+ test_commit -C upgrade base no-high-bits &&
+
+ git -C upgrade config --add commitgraph.changedPathsVersion 1 &&
+ GIT_TRACE2_EVENT="$(pwd)/trace2.txt" \
+ git -C upgrade commit-graph write --reachable --changed-paths &&
+ test_filter_computed 1 trace2.txt &&
+ test_filter_upgraded 0 trace2.txt &&
+
+ git -C upgrade config --add commitgraph.changedPathsVersion 2 &&
+ GIT_TRACE2_EVENT="$(pwd)/trace2.txt" \
+ git -C upgrade commit-graph write --reachable --changed-paths &&
+ test_filter_computed 0 trace2.txt &&
+ test_filter_upgraded 1 trace2.txt
+'
+
test_done
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 08/17] t4216: test changed path filters with high bit paths
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
From: Jonathan Tan <jonathantanmy@google.com>
Subsequent commits will teach Git another version of changed path
filter that has different behavior with paths that contain at least
one character with its high bit set, so test the existing behavior as
a baseline.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
t/t4216-log-bloom.sh | 52 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 52 insertions(+)
diff --git a/t/t4216-log-bloom.sh b/t/t4216-log-bloom.sh
index f49a8f2fbf..da67c40134 100755
--- a/t/t4216-log-bloom.sh
+++ b/t/t4216-log-bloom.sh
@@ -484,4 +484,56 @@ test_expect_success 'merge graph layers with incompatible Bloom settings' '
! grep "disabling Bloom filters" err
'
+get_first_changed_path_filter () {
+ test-tool read-graph bloom-filters >filters.dat &&
+ head -n 1 filters.dat
+}
+
+# chosen to be the same under all Unicode normalization forms
+CENT=$(printf "\302\242")
+
+test_expect_success 'set up repo with high bit path, version 1 changed-path' '
+ git init highbit1 &&
+ test_commit -C highbit1 c1 "$CENT" &&
+ git -C highbit1 commit-graph write --reachable --changed-paths
+'
+
+test_expect_success 'setup check value of version 1 changed-path' '
+ (
+ cd highbit1 &&
+ echo "52a9" >expect &&
+ get_first_changed_path_filter >actual &&
+ test_cmp expect actual
+ )
+'
+
+# expect will not match actual if char is unsigned by default. Write the test
+# in this way, so that a user running this test script can still see if the two
+# files match. (It will appear as an ordinary success if they match, and a skip
+# if not.)
+if test_cmp highbit1/expect highbit1/actual
+then
+ test_set_prereq SIGNED_CHAR_BY_DEFAULT
+fi
+test_expect_success SIGNED_CHAR_BY_DEFAULT 'check value of version 1 changed-path' '
+ # Only the prereq matters for this test.
+ true
+'
+
+test_expect_success 'setup make another commit' '
+ # "git log" does not use Bloom filters for root commits - see how, in
+ # revision.c, rev_compare_tree() (the only code path that eventually calls
+ # get_bloom_filter()) is only called by try_to_simplify_commit() when the commit
+ # has one parent. Therefore, make another commit so that we perform the tests on
+ # a non-root commit.
+ test_commit -C highbit1 anotherc1 "another$CENT"
+'
+
+test_expect_success 'version 1 changed-path used when version 1 requested' '
+ (
+ cd highbit1 &&
+ test_bloom_filters_used "-- another$CENT"
+ )
+'
+
test_done
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 10/17] commit-graph: new filter ver. that fixes murmur3
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
From: Jonathan Tan <jonathantanmy@google.com>
The murmur3 implementation in bloom.c has a bug when converting series
of 4 bytes into network-order integers when char is signed (which is
controllable by a compiler option, and the default signedness of char is
platform-specific). When a string contains characters with the high bit
set, this bug causes results that, although internally consistent within
Git, does not accord with other implementations of murmur3 (thus,
the changed path filters wouldn't be readable by other off-the-shelf
implementatios of murmur3) and even with Git binaries that were compiled
with different signedness of char. This bug affects both how Git writes
changed path filters to disk and how Git interprets changed path filters
on disk.
Therefore, introduce a new version (2) of changed path filters that
corrects this problem. The existing version (1) is still supported and
is still the default, but users should migrate away from it as soon
as possible.
Because this bug only manifests with characters that have the high bit
set, it may be possible that some (or all) commits in a given repo would
have the same changed path filter both before and after this fix is
applied. However, in order to determine whether this is the case, the
changed paths would first have to be computed, at which point it is not
much more expensive to just compute a new changed path filter.
So this patch does not include any mechanism to "salvage" changed path
filters from repositories. There is also no "mixed" mode - for each
invocation of Git, reading and writing changed path filters are done
with the same version number; this version number may be explicitly
stated (typically if the user knows which version they need) or
automatically determined from the version of the existing changed path
filters in the repository.
There is a change in write_commit_graph(). graph_read_bloom_data()
makes it possible for chunk_bloom_data to be non-NULL but
bloom_filter_settings to be NULL, which causes a segfault later on. I
produced such a segfault while developing this patch, but couldn't find
a way to reproduce it neither after this complete patch (or before),
but in any case it seemed like a good thing to include that might help
future patch authors.
The value in t0095 was obtained from another murmur3 implementation
using the following Go source code:
package main
import "fmt"
import "github.com/spaolacci/murmur3"
func main() {
fmt.Printf("%x\n", murmur3.Sum32([]byte("Hello world!")))
fmt.Printf("%x\n", murmur3.Sum32([]byte{0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff}))
}
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
Documentation/config/commitgraph.txt | 5 +-
bloom.c | 69 +++++++++++++++++-
bloom.h | 8 +-
commit-graph.c | 32 ++++++--
t/helper/test-bloom.c | 9 ++-
t/t0095-bloom.sh | 8 ++
t/t4216-log-bloom.sh | 105 +++++++++++++++++++++++++++
7 files changed, 223 insertions(+), 13 deletions(-)
diff --git a/Documentation/config/commitgraph.txt b/Documentation/config/commitgraph.txt
index 2dc9170622..acc74a2f27 100644
--- a/Documentation/config/commitgraph.txt
+++ b/Documentation/config/commitgraph.txt
@@ -15,7 +15,7 @@ commitGraph.readChangedPaths::
commitGraph.changedPathsVersion::
Specifies the version of the changed-path Bloom filters that Git will read and
- write. May be -1, 0 or 1.
+ write. May be -1, 0, 1, or 2.
+
Defaults to -1.
+
@@ -28,4 +28,7 @@ filters when instructed to write.
If 1, Git will only read version 1 Bloom filters, and will write version 1
Bloom filters.
+
+If 2, Git will only read version 2 Bloom filters, and will write version 2
+Bloom filters.
++
See linkgit:git-commit-graph[1] for more information.
diff --git a/bloom.c b/bloom.c
index 3e78cfe79d..ebef5cfd2f 100644
--- a/bloom.c
+++ b/bloom.c
@@ -66,7 +66,64 @@ int load_bloom_filter_from_graph(struct commit_graph *g,
* Not considered to be cryptographically secure.
* Implemented as described in https://en.wikipedia.org/wiki/MurmurHash#Algorithm
*/
-uint32_t murmur3_seeded(uint32_t seed, const char *data, size_t len)
+uint32_t murmur3_seeded_v2(uint32_t seed, const char *data, size_t len)
+{
+ const uint32_t c1 = 0xcc9e2d51;
+ const uint32_t c2 = 0x1b873593;
+ const uint32_t r1 = 15;
+ const uint32_t r2 = 13;
+ const uint32_t m = 5;
+ const uint32_t n = 0xe6546b64;
+ int i;
+ uint32_t k1 = 0;
+ const char *tail;
+
+ int len4 = len / sizeof(uint32_t);
+
+ uint32_t k;
+ for (i = 0; i < len4; i++) {
+ uint32_t byte1 = (uint32_t)(unsigned char)data[4*i];
+ uint32_t byte2 = ((uint32_t)(unsigned char)data[4*i + 1]) << 8;
+ uint32_t byte3 = ((uint32_t)(unsigned char)data[4*i + 2]) << 16;
+ uint32_t byte4 = ((uint32_t)(unsigned char)data[4*i + 3]) << 24;
+ k = byte1 | byte2 | byte3 | byte4;
+ k *= c1;
+ k = rotate_left(k, r1);
+ k *= c2;
+
+ seed ^= k;
+ seed = rotate_left(seed, r2) * m + n;
+ }
+
+ tail = (data + len4 * sizeof(uint32_t));
+
+ switch (len & (sizeof(uint32_t) - 1)) {
+ case 3:
+ k1 ^= ((uint32_t)(unsigned char)tail[2]) << 16;
+ /*-fallthrough*/
+ case 2:
+ k1 ^= ((uint32_t)(unsigned char)tail[1]) << 8;
+ /*-fallthrough*/
+ case 1:
+ k1 ^= ((uint32_t)(unsigned char)tail[0]) << 0;
+ k1 *= c1;
+ k1 = rotate_left(k1, r1);
+ k1 *= c2;
+ seed ^= k1;
+ break;
+ }
+
+ seed ^= (uint32_t)len;
+ seed ^= (seed >> 16);
+ seed *= 0x85ebca6b;
+ seed ^= (seed >> 13);
+ seed *= 0xc2b2ae35;
+ seed ^= (seed >> 16);
+
+ return seed;
+}
+
+static uint32_t murmur3_seeded_v1(uint32_t seed, const char *data, size_t len)
{
const uint32_t c1 = 0xcc9e2d51;
const uint32_t c2 = 0x1b873593;
@@ -131,8 +188,14 @@ void fill_bloom_key(const char *data,
int i;
const uint32_t seed0 = 0x293ae76f;
const uint32_t seed1 = 0x7e646e2c;
- const uint32_t hash0 = murmur3_seeded(seed0, data, len);
- const uint32_t hash1 = murmur3_seeded(seed1, data, len);
+ uint32_t hash0, hash1;
+ if (settings->hash_version == 2) {
+ hash0 = murmur3_seeded_v2(seed0, data, len);
+ hash1 = murmur3_seeded_v2(seed1, data, len);
+ } else {
+ hash0 = murmur3_seeded_v1(seed0, data, len);
+ hash1 = murmur3_seeded_v1(seed1, data, len);
+ }
key->hashes = (uint32_t *)xcalloc(settings->num_hashes, sizeof(uint32_t));
for (i = 0; i < settings->num_hashes; i++)
diff --git a/bloom.h b/bloom.h
index 1e4f612d2c..138d57a86b 100644
--- a/bloom.h
+++ b/bloom.h
@@ -8,9 +8,11 @@ struct commit_graph;
struct bloom_filter_settings {
/*
* The version of the hashing technique being used.
- * We currently only support version = 1 which is
+ * The newest version is 2, which is
* the seeded murmur3 hashing technique implemented
- * in bloom.c.
+ * in bloom.c. Bloom filters of version 1 were created
+ * with prior versions of Git, which had a bug in the
+ * implementation of the hash function.
*/
uint32_t hash_version;
@@ -80,7 +82,7 @@ int load_bloom_filter_from_graph(struct commit_graph *g,
* Not considered to be cryptographically secure.
* Implemented as described in https://en.wikipedia.org/wiki/MurmurHash#Algorithm
*/
-uint32_t murmur3_seeded(uint32_t seed, const char *data, size_t len);
+uint32_t murmur3_seeded_v2(uint32_t seed, const char *data, size_t len);
void fill_bloom_key(const char *data,
size_t len,
diff --git a/commit-graph.c b/commit-graph.c
index ea677c87fb..db623afd09 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -314,17 +314,26 @@ static int graph_read_oid_lookup(const unsigned char *chunk_start,
return 0;
}
+struct graph_read_bloom_data_context {
+ struct commit_graph *g;
+ int *commit_graph_changed_paths_version;
+};
+
static int graph_read_bloom_data(const unsigned char *chunk_start,
size_t chunk_size, void *data)
{
- struct commit_graph *g = data;
+ struct graph_read_bloom_data_context *c = data;
+ struct commit_graph *g = c->g;
uint32_t hash_version;
- g->chunk_bloom_data = chunk_start;
hash_version = get_be32(chunk_start);
- if (hash_version != 1)
+ if (*c->commit_graph_changed_paths_version == -1) {
+ *c->commit_graph_changed_paths_version = hash_version;
+ } else if (hash_version != *c->commit_graph_changed_paths_version) {
return 0;
+ }
+ g->chunk_bloom_data = chunk_start;
g->bloom_filter_settings = xmalloc(sizeof(struct bloom_filter_settings));
g->bloom_filter_settings->hash_version = hash_version;
g->bloom_filter_settings->num_hashes = get_be32(chunk_start + 4);
@@ -412,10 +421,14 @@ struct commit_graph *parse_commit_graph(struct repo_settings *s,
}
if (s->commit_graph_changed_paths_version) {
+ struct graph_read_bloom_data_context context = {
+ .g = graph,
+ .commit_graph_changed_paths_version = &s->commit_graph_changed_paths_version
+ };
pair_chunk(cf, GRAPH_CHUNKID_BLOOMINDEXES,
&graph->chunk_bloom_indexes);
read_chunk(cf, GRAPH_CHUNKID_BLOOMDATA,
- graph_read_bloom_data, graph);
+ graph_read_bloom_data, &context);
}
if (graph->chunk_bloom_indexes && graph->chunk_bloom_data) {
@@ -2441,6 +2454,13 @@ int write_commit_graph(struct object_directory *odb,
}
if (!commit_graph_compatible(r))
return 0;
+ if (r->settings.commit_graph_changed_paths_version < -1
+ || r->settings.commit_graph_changed_paths_version > 2) {
+ warning(_("attempting to write a commit-graph, but "
+ "'commitgraph.changedPathsVersion' (%d) is not supported"),
+ r->settings.commit_graph_changed_paths_version);
+ return 0;
+ }
CALLOC_ARRAY(ctx, 1);
ctx->r = r;
@@ -2453,6 +2473,8 @@ int write_commit_graph(struct object_directory *odb,
ctx->write_generation_data = (get_configured_generation_version(r) == 2);
ctx->num_generation_data_overflows = 0;
+ bloom_settings.hash_version = r->settings.commit_graph_changed_paths_version == 2
+ ? 2 : 1;
bloom_settings.bits_per_entry = git_env_ulong("GIT_TEST_BLOOM_SETTINGS_BITS_PER_ENTRY",
bloom_settings.bits_per_entry);
bloom_settings.num_hashes = git_env_ulong("GIT_TEST_BLOOM_SETTINGS_NUM_HASHES",
@@ -2482,7 +2504,7 @@ int write_commit_graph(struct object_directory *odb,
g = ctx->r->objects->commit_graph;
/* We have changed-paths already. Keep them in the next graph */
- if (g && g->chunk_bloom_data) {
+ if (g && g->bloom_filter_settings) {
ctx->changed_paths = 1;
ctx->bloom_settings = g->bloom_filter_settings;
}
diff --git a/t/helper/test-bloom.c b/t/helper/test-bloom.c
index aabe31d724..3cbc0a5b50 100644
--- a/t/helper/test-bloom.c
+++ b/t/helper/test-bloom.c
@@ -50,6 +50,7 @@ static void get_bloom_filter_for_commit(const struct object_id *commit_oid)
static const char *bloom_usage = "\n"
" test-tool bloom get_murmur3 <string>\n"
+" test-tool bloom get_murmur3_seven_highbit\n"
" test-tool bloom generate_filter <string> [<string>...]\n"
" test-tool bloom get_filter_for_commit <commit-hex>\n";
@@ -64,7 +65,13 @@ int cmd__bloom(int argc, const char **argv)
uint32_t hashed;
if (argc < 3)
usage(bloom_usage);
- hashed = murmur3_seeded(0, argv[2], strlen(argv[2]));
+ hashed = murmur3_seeded_v2(0, argv[2], strlen(argv[2]));
+ printf("Murmur3 Hash with seed=0:0x%08x\n", hashed);
+ }
+
+ if (!strcmp(argv[1], "get_murmur3_seven_highbit")) {
+ uint32_t hashed;
+ hashed = murmur3_seeded_v2(0, "\x99\xaa\xbb\xcc\xdd\xee\xff", 7);
printf("Murmur3 Hash with seed=0:0x%08x\n", hashed);
}
diff --git a/t/t0095-bloom.sh b/t/t0095-bloom.sh
index b567383eb8..c8d84ab606 100755
--- a/t/t0095-bloom.sh
+++ b/t/t0095-bloom.sh
@@ -29,6 +29,14 @@ test_expect_success 'compute unseeded murmur3 hash for test string 2' '
test_cmp expect actual
'
+test_expect_success 'compute unseeded murmur3 hash for test string 3' '
+ cat >expect <<-\EOF &&
+ Murmur3 Hash with seed=0:0xa183ccfd
+ EOF
+ test-tool bloom get_murmur3_seven_highbit >actual &&
+ test_cmp expect actual
+'
+
test_expect_success 'compute bloom key for empty string' '
cat >expect <<-\EOF &&
Hashes:0x5615800c|0x5b966560|0x61174ab4|0x66983008|0x6c19155c|0x7199fab0|0x771ae004|
diff --git a/t/t4216-log-bloom.sh b/t/t4216-log-bloom.sh
index da67c40134..8f8b5d4966 100755
--- a/t/t4216-log-bloom.sh
+++ b/t/t4216-log-bloom.sh
@@ -536,4 +536,109 @@ test_expect_success 'version 1 changed-path used when version 1 requested' '
)
'
+test_expect_success 'version 1 changed-path not used when version 2 requested' '
+ (
+ cd highbit1 &&
+ git config --add commitgraph.changedPathsVersion 2 &&
+ test_bloom_filters_not_used "-- another$CENT"
+ )
+'
+
+test_expect_success 'version 1 changed-path used when autodetect requested' '
+ (
+ cd highbit1 &&
+ git config --add commitgraph.changedPathsVersion -1 &&
+ test_bloom_filters_used "-- another$CENT"
+ )
+'
+
+test_expect_success 'when writing another commit graph, preserve existing version 1 of changed-path' '
+ test_commit -C highbit1 c1double "$CENT$CENT" &&
+ git -C highbit1 commit-graph write --reachable --changed-paths &&
+ (
+ cd highbit1 &&
+ git config --add commitgraph.changedPathsVersion -1 &&
+ echo "options: bloom(1,10,7) read_generation_data" >expect &&
+ test-tool read-graph >full &&
+ grep options full >actual &&
+ test_cmp expect actual
+ )
+'
+
+test_expect_success 'set up repo with high bit path, version 2 changed-path' '
+ git init highbit2 &&
+ git -C highbit2 config --add commitgraph.changedPathsVersion 2 &&
+ test_commit -C highbit2 c2 "$CENT" &&
+ git -C highbit2 commit-graph write --reachable --changed-paths
+'
+
+test_expect_success 'check value of version 2 changed-path' '
+ (
+ cd highbit2 &&
+ echo "c01f" >expect &&
+ get_first_changed_path_filter >actual &&
+ test_cmp expect actual
+ )
+'
+
+test_expect_success 'setup make another commit' '
+ # "git log" does not use Bloom filters for root commits - see how, in
+ # revision.c, rev_compare_tree() (the only code path that eventually calls
+ # get_bloom_filter()) is only called by try_to_simplify_commit() when the commit
+ # has one parent. Therefore, make another commit so that we perform the tests on
+ # a non-root commit.
+ test_commit -C highbit2 anotherc2 "another$CENT"
+'
+
+test_expect_success 'version 2 changed-path used when version 2 requested' '
+ (
+ cd highbit2 &&
+ test_bloom_filters_used "-- another$CENT"
+ )
+'
+
+test_expect_success 'version 2 changed-path not used when version 1 requested' '
+ (
+ cd highbit2 &&
+ git config --add commitgraph.changedPathsVersion 1 &&
+ test_bloom_filters_not_used "-- another$CENT"
+ )
+'
+
+test_expect_success 'version 2 changed-path used when autodetect requested' '
+ (
+ cd highbit2 &&
+ git config --add commitgraph.changedPathsVersion -1 &&
+ test_bloom_filters_used "-- another$CENT"
+ )
+'
+
+test_expect_success 'when writing another commit graph, preserve existing version 2 of changed-path' '
+ test_commit -C highbit2 c2double "$CENT$CENT" &&
+ git -C highbit2 commit-graph write --reachable --changed-paths &&
+ (
+ cd highbit2 &&
+ git config --add commitgraph.changedPathsVersion -1 &&
+ echo "options: bloom(2,10,7) read_generation_data" >expect &&
+ test-tool read-graph >full &&
+ grep options full >actual &&
+ test_cmp expect actual
+ )
+'
+
+test_expect_success 'when writing commit graph, do not reuse changed-path of another version' '
+ git init doublewrite &&
+ test_commit -C doublewrite c "$CENT" &&
+ git -C doublewrite config --add commitgraph.changedPathsVersion 1 &&
+ git -C doublewrite commit-graph write --reachable --changed-paths &&
+ git -C doublewrite config --add commitgraph.changedPathsVersion 2 &&
+ git -C doublewrite commit-graph write --reachable --changed-paths &&
+ (
+ cd doublewrite &&
+ echo "c01f" >expect &&
+ get_first_changed_path_filter >actual &&
+ test_cmp expect actual
+ )
+'
+
test_done
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 14/17] commit-graph: drop unnecessary `graph_read_bloom_data_context`
From: Taylor Blau @ 2023-10-10 20:34 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
The `graph_read_bloom_data_context` struct was introduced in an earlier
commit in order to pass pointers to the commit-graph and changed-path
Bloom filter version when reading the BDAT chunk.
The previous commit no longer writes through the changed_paths_version
pointer, making the surrounding context structure unnecessary. Drop it
and pass a pointer to the commit-graph directly when reading the BDAT
chunk.
Noticed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
commit-graph.c | 14 ++------------
1 file changed, 2 insertions(+), 12 deletions(-)
diff --git a/commit-graph.c b/commit-graph.c
index fa3b58e762..e0fc62e110 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -314,16 +314,10 @@ static int graph_read_oid_lookup(const unsigned char *chunk_start,
return 0;
}
-struct graph_read_bloom_data_context {
- struct commit_graph *g;
- int *commit_graph_changed_paths_version;
-};
-
static int graph_read_bloom_data(const unsigned char *chunk_start,
size_t chunk_size, void *data)
{
- struct graph_read_bloom_data_context *c = data;
- struct commit_graph *g = c->g;
+ struct commit_graph *g = data;
uint32_t hash_version;
hash_version = get_be32(chunk_start);
@@ -415,14 +409,10 @@ struct commit_graph *parse_commit_graph(struct repo_settings *s,
}
if (s->commit_graph_changed_paths_version) {
- struct graph_read_bloom_data_context context = {
- .g = graph,
- .commit_graph_changed_paths_version = &s->commit_graph_changed_paths_version
- };
pair_chunk(cf, GRAPH_CHUNKID_BLOOMINDEXES,
&graph->chunk_bloom_indexes);
read_chunk(cf, GRAPH_CHUNKID_BLOOMDATA,
- graph_read_bloom_data, &context);
+ graph_read_bloom_data, graph);
}
if (graph->chunk_bloom_indexes && graph->chunk_bloom_data) {
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 11/17] bloom: annotate filters with hash version
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
In subsequent commits, we will want to load existing Bloom filters out
of a commit-graph, even when the hash version they were computed with
does not match the value of `commitGraph.changedPathVersion`.
In order to differentiate between the two, add a "version" field to each
Bloom filter.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
bloom.c | 11 ++++++++---
bloom.h | 1 +
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/bloom.c b/bloom.c
index ebef5cfd2f..9b6a30f6f6 100644
--- a/bloom.c
+++ b/bloom.c
@@ -55,6 +55,7 @@ int load_bloom_filter_from_graph(struct commit_graph *g,
filter->data = (unsigned char *)(g->chunk_bloom_data +
sizeof(unsigned char) * start_index +
BLOOMDATA_CHUNK_HEADER_SIZE);
+ filter->version = g->bloom_filter_settings->hash_version;
return 1;
}
@@ -240,11 +241,13 @@ static int pathmap_cmp(const void *hashmap_cmp_fn_data UNUSED,
return strcmp(e1->path, e2->path);
}
-static void init_truncated_large_filter(struct bloom_filter *filter)
+static void init_truncated_large_filter(struct bloom_filter *filter,
+ int version)
{
filter->data = xmalloc(1);
filter->data[0] = 0xFF;
filter->len = 1;
+ filter->version = version;
}
struct bloom_filter *get_or_compute_bloom_filter(struct repository *r,
@@ -329,13 +332,15 @@ struct bloom_filter *get_or_compute_bloom_filter(struct repository *r,
}
if (hashmap_get_size(&pathmap) > settings->max_changed_paths) {
- init_truncated_large_filter(filter);
+ init_truncated_large_filter(filter,
+ settings->hash_version);
if (computed)
*computed |= BLOOM_TRUNC_LARGE;
goto cleanup;
}
filter->len = (hashmap_get_size(&pathmap) * settings->bits_per_entry + BITS_PER_WORD - 1) / BITS_PER_WORD;
+ filter->version = settings->hash_version;
if (!filter->len) {
if (computed)
*computed |= BLOOM_TRUNC_EMPTY;
@@ -355,7 +360,7 @@ struct bloom_filter *get_or_compute_bloom_filter(struct repository *r,
} else {
for (i = 0; i < diff_queued_diff.nr; i++)
diff_free_filepair(diff_queued_diff.queue[i]);
- init_truncated_large_filter(filter);
+ init_truncated_large_filter(filter, settings->hash_version);
if (computed)
*computed |= BLOOM_TRUNC_LARGE;
diff --git a/bloom.h b/bloom.h
index 138d57a86b..330a140520 100644
--- a/bloom.h
+++ b/bloom.h
@@ -55,6 +55,7 @@ struct bloom_filter_settings {
struct bloom_filter {
unsigned char *data;
size_t len;
+ int version;
};
/*
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 13/17] commit-graph.c: unconditionally load Bloom filters
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
In 9e4df4da07 (commit-graph: new filter ver. that fixes murmur3,
2023-08-01), we began ignoring the Bloom data ("BDAT") chunk for
commit-graphs whose Bloom filters were computed using a hash version
incompatible with the value of `commitGraph.changedPathVersion`.
Now that the Bloom API has been hardened to discard these incompatible
filters (with the exception of low-level APIs), we can safely load these
Bloom filters unconditionally.
We no longer want to return early from `graph_read_bloom_data()`, and
similarly do not want to set the bloom_settings' `hash_version` field as
a side-effect. The latter is because we want to wait until we know which
Bloom settings we're using (either the defaults, from the GIT_TEST
variables, or from the previous commit-graph layer) before deciding what
hash_version to use.
If we detect an existing BDAT chunk, we'll infer the rest of the
settings (e.g., number of hashes, bits per entry, and maximum number of
changed paths) from the earlier graph layer. The hash_version will be
inferred from the previous layer as well, unless one has already been
specified via configuration.
Once all of that is done, we normalize the value of the hash_version to
either "1" or "2".
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
commit-graph.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/commit-graph.c b/commit-graph.c
index db623afd09..fa3b58e762 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -327,12 +327,6 @@ static int graph_read_bloom_data(const unsigned char *chunk_start,
uint32_t hash_version;
hash_version = get_be32(chunk_start);
- if (*c->commit_graph_changed_paths_version == -1) {
- *c->commit_graph_changed_paths_version = hash_version;
- } else if (hash_version != *c->commit_graph_changed_paths_version) {
- return 0;
- }
-
g->chunk_bloom_data = chunk_start;
g->bloom_filter_settings = xmalloc(sizeof(struct bloom_filter_settings));
g->bloom_filter_settings->hash_version = hash_version;
@@ -2473,8 +2467,7 @@ int write_commit_graph(struct object_directory *odb,
ctx->write_generation_data = (get_configured_generation_version(r) == 2);
ctx->num_generation_data_overflows = 0;
- bloom_settings.hash_version = r->settings.commit_graph_changed_paths_version == 2
- ? 2 : 1;
+ bloom_settings.hash_version = r->settings.commit_graph_changed_paths_version;
bloom_settings.bits_per_entry = git_env_ulong("GIT_TEST_BLOOM_SETTINGS_BITS_PER_ENTRY",
bloom_settings.bits_per_entry);
bloom_settings.num_hashes = git_env_ulong("GIT_TEST_BLOOM_SETTINGS_NUM_HASHES",
@@ -2506,10 +2499,18 @@ int write_commit_graph(struct object_directory *odb,
/* We have changed-paths already. Keep them in the next graph */
if (g && g->bloom_filter_settings) {
ctx->changed_paths = 1;
- ctx->bloom_settings = g->bloom_filter_settings;
+
+ /* don't propagate the hash_version unless unspecified */
+ if (bloom_settings.hash_version == -1)
+ bloom_settings.hash_version = g->bloom_filter_settings->hash_version;
+ bloom_settings.bits_per_entry = g->bloom_filter_settings->bits_per_entry;
+ bloom_settings.num_hashes = g->bloom_filter_settings->num_hashes;
+ bloom_settings.max_changed_paths = g->bloom_filter_settings->max_changed_paths;
}
}
+ bloom_settings.hash_version = bloom_settings.hash_version == 2 ? 2 : 1;
+
if (ctx->split) {
struct commit_graph *g = ctx->r->objects->commit_graph;
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 12/17] bloom: prepare to discard incompatible Bloom filters
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
Callers use the inline `get_bloom_filter()` implementation as a thin
wrapper around `get_or_compute_bloom_filter()`. The former calls the
latter with a value of "0" for `compute_if_not_present`, making
`get_bloom_filter()` the default read-only path for fetching an existing
Bloom filter.
Callers expect the value returned from `get_bloom_filter()` is usable,
that is that it's compatible with the configured value corresponding to
`commitGraph.changedPathsVersion`.
This is OK, since the commit-graph machinery only initializes its BDAT
chunk (thereby enabling it to service Bloom filter queries) when the
Bloom filter hash_version is compatible with our settings. So any value
returned by `get_bloom_filter()` is trivially useable.
However, subsequent commits will load the BDAT chunk even when the Bloom
filters are built with incompatible hash versions. Prepare to handle
this by teaching `get_bloom_filter()` to discard filters that are
incompatible with the configured hash version.
Callers who wish to read incompatible filters (e.g., for upgrading
filters from v1 to v2) may use the lower level routine,
`get_or_compute_bloom_filter()`.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
bloom.c | 20 +++++++++++++++++++-
bloom.h | 20 ++++++++++++++++++--
2 files changed, 37 insertions(+), 3 deletions(-)
diff --git a/bloom.c b/bloom.c
index 9b6a30f6f6..739fa093ba 100644
--- a/bloom.c
+++ b/bloom.c
@@ -250,6 +250,23 @@ static void init_truncated_large_filter(struct bloom_filter *filter,
filter->version = version;
}
+struct bloom_filter *get_bloom_filter(struct repository *r, struct commit *c)
+{
+ struct bloom_filter *filter;
+ int hash_version;
+
+ filter = get_or_compute_bloom_filter(r, c, 0, NULL, NULL);
+ if (!filter)
+ return NULL;
+
+ prepare_repo_settings(r);
+ hash_version = r->settings.commit_graph_changed_paths_version;
+
+ if (!(hash_version == -1 || hash_version == filter->version))
+ return NULL; /* unusable filter */
+ return filter;
+}
+
struct bloom_filter *get_or_compute_bloom_filter(struct repository *r,
struct commit *c,
int compute_if_not_present,
@@ -275,7 +292,8 @@ struct bloom_filter *get_or_compute_bloom_filter(struct repository *r,
filter, graph_pos);
}
- if (filter->data && filter->len)
+ if ((filter->data && filter->len) &&
+ (!settings || settings->hash_version == filter->version))
return filter;
if (!compute_if_not_present)
return NULL;
diff --git a/bloom.h b/bloom.h
index 330a140520..bfe389e29c 100644
--- a/bloom.h
+++ b/bloom.h
@@ -110,8 +110,24 @@ struct bloom_filter *get_or_compute_bloom_filter(struct repository *r,
const struct bloom_filter_settings *settings,
enum bloom_filter_computed *computed);
-#define get_bloom_filter(r, c) get_or_compute_bloom_filter( \
- (r), (c), 0, NULL, NULL)
+/*
+ * Find the Bloom filter associated with the given commit "c".
+ *
+ * If any of the following are true
+ *
+ * - the repository does not have a commit-graph, or
+ * - the repository disables reading from the commit-graph, or
+ * - the given commit does not have a Bloom filter computed, or
+ * - there is a Bloom filter for commit "c", but it cannot be read
+ * because the filter uses an incompatible version of murmur3
+ *
+ * , then `get_bloom_filter()` will return NULL. Otherwise, the corresponding
+ * Bloom filter will be returned.
+ *
+ * For callers who wish to inspect Bloom filters with incompatible hash
+ * versions, use get_or_compute_bloom_filter().
+ */
+struct bloom_filter *get_bloom_filter(struct repository *r, struct commit *c);
int bloom_filter_contains(const struct bloom_filter *filter,
const struct bloom_key *key,
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 15/17] object.h: fix mis-aligned flag bits table
From: Taylor Blau @ 2023-10-10 20:34 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
Bit position 23 is one column too far to the left.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
object.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/object.h b/object.h
index 114d45954d..db25714b4e 100644
--- a/object.h
+++ b/object.h
@@ -62,7 +62,7 @@ void object_array_init(struct object_array *array);
/*
* object flag allocation:
- * revision.h: 0---------10 15 23------27
+ * revision.h: 0---------10 15 23------27
* fetch-pack.c: 01 67
* negotiator/default.c: 2--5
* walker.c: 0-2
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 09/17] repo-settings: introduce commitgraph.changedPathsVersion
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
From: Jonathan Tan <jonathantanmy@google.com>
A subsequent commit will introduce another version of the changed-path
filter in the commit graph file. In order to control which version to
write (and read), a config variable is needed.
Therefore, introduce this config variable. For forwards compatibility,
teach Git to not read commit graphs when the config variable
is set to an unsupported version. Because we teach Git this,
commitgraph.readChangedPaths is now redundant, so deprecate it and
define its behavior in terms of the config variable we introduce.
This commit does not change the behavior of writing (Git writes changed
path filters when explicitly instructed regardless of any config
variable), but a subsequent commit will restrict Git such that it will
only write when commitgraph.changedPathsVersion is a recognized value.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
Documentation/config/commitgraph.txt | 23 ++++++++++++++++++++---
commit-graph.c | 2 +-
oss-fuzz/fuzz-commit-graph.c | 2 +-
repo-settings.c | 6 +++++-
repository.h | 2 +-
5 files changed, 28 insertions(+), 7 deletions(-)
diff --git a/Documentation/config/commitgraph.txt b/Documentation/config/commitgraph.txt
index 30604e4a4c..2dc9170622 100644
--- a/Documentation/config/commitgraph.txt
+++ b/Documentation/config/commitgraph.txt
@@ -9,6 +9,23 @@ commitGraph.maxNewFilters::
commit-graph write` (c.f., linkgit:git-commit-graph[1]).
commitGraph.readChangedPaths::
- If true, then git will use the changed-path Bloom filters in the
- commit-graph file (if it exists, and they are present). Defaults to
- true. See linkgit:git-commit-graph[1] for more information.
+ Deprecated. Equivalent to commitGraph.changedPathsVersion=-1 if true, and
+ commitGraph.changedPathsVersion=0 if false. (If commitGraph.changedPathVersion
+ is also set, commitGraph.changedPathsVersion takes precedence.)
+
+commitGraph.changedPathsVersion::
+ Specifies the version of the changed-path Bloom filters that Git will read and
+ write. May be -1, 0 or 1.
++
+Defaults to -1.
++
+If -1, Git will use the version of the changed-path Bloom filters in the
+repository, defaulting to 1 if there are none.
++
+If 0, Git will not read any Bloom filters, and will write version 1 Bloom
+filters when instructed to write.
++
+If 1, Git will only read version 1 Bloom filters, and will write version 1
+Bloom filters.
++
+See linkgit:git-commit-graph[1] for more information.
diff --git a/commit-graph.c b/commit-graph.c
index ae0902f7f4..ea677c87fb 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -411,7 +411,7 @@ struct commit_graph *parse_commit_graph(struct repo_settings *s,
graph->read_generation_data = 1;
}
- if (s->commit_graph_read_changed_paths) {
+ if (s->commit_graph_changed_paths_version) {
pair_chunk(cf, GRAPH_CHUNKID_BLOOMINDEXES,
&graph->chunk_bloom_indexes);
read_chunk(cf, GRAPH_CHUNKID_BLOOMDATA,
diff --git a/oss-fuzz/fuzz-commit-graph.c b/oss-fuzz/fuzz-commit-graph.c
index 2992079dd9..325c0b991a 100644
--- a/oss-fuzz/fuzz-commit-graph.c
+++ b/oss-fuzz/fuzz-commit-graph.c
@@ -19,7 +19,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
* possible.
*/
the_repository->settings.commit_graph_generation_version = 2;
- the_repository->settings.commit_graph_read_changed_paths = 1;
+ the_repository->settings.commit_graph_changed_paths_version = 1;
g = parse_commit_graph(&the_repository->settings, (void *)data, size);
repo_clear(the_repository);
free_commit_graph(g);
diff --git a/repo-settings.c b/repo-settings.c
index 525f69c0c7..db8fe817f3 100644
--- a/repo-settings.c
+++ b/repo-settings.c
@@ -24,6 +24,7 @@ void prepare_repo_settings(struct repository *r)
int value;
const char *strval;
int manyfiles;
+ int read_changed_paths;
if (!r->gitdir)
BUG("Cannot add settings for uninitialized repository");
@@ -54,7 +55,10 @@ void prepare_repo_settings(struct repository *r)
/* Commit graph config or default, does not cascade (simple) */
repo_cfg_bool(r, "core.commitgraph", &r->settings.core_commit_graph, 1);
repo_cfg_int(r, "commitgraph.generationversion", &r->settings.commit_graph_generation_version, 2);
- repo_cfg_bool(r, "commitgraph.readchangedpaths", &r->settings.commit_graph_read_changed_paths, 1);
+ repo_cfg_bool(r, "commitgraph.readchangedpaths", &read_changed_paths, 1);
+ repo_cfg_int(r, "commitgraph.changedpathsversion",
+ &r->settings.commit_graph_changed_paths_version,
+ read_changed_paths ? -1 : 0);
repo_cfg_bool(r, "gc.writecommitgraph", &r->settings.gc_write_commit_graph, 1);
repo_cfg_bool(r, "fetch.writecommitgraph", &r->settings.fetch_write_commit_graph, 0);
diff --git a/repository.h b/repository.h
index 5f18486f64..f71154e12c 100644
--- a/repository.h
+++ b/repository.h
@@ -29,7 +29,7 @@ struct repo_settings {
int core_commit_graph;
int commit_graph_generation_version;
- int commit_graph_read_changed_paths;
+ int commit_graph_changed_paths_version;
int gc_write_commit_graph;
int fetch_write_commit_graph;
int command_requires_full_index;
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 07/17] t/helper/test-read-graph: implement `bloom-filters` mode
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
Implement a mode of the "read-graph" test helper to dump out the
hexadecimal contents of the Bloom filter(s) contained in a commit-graph.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
t/helper/test-read-graph.c | 44 +++++++++++++++++++++++++++++++++-----
1 file changed, 39 insertions(+), 5 deletions(-)
diff --git a/t/helper/test-read-graph.c b/t/helper/test-read-graph.c
index 3375392f6c..da9ac8584d 100644
--- a/t/helper/test-read-graph.c
+++ b/t/helper/test-read-graph.c
@@ -47,10 +47,32 @@ static void dump_graph_info(struct commit_graph *graph)
printf("\n");
}
-int cmd__read_graph(int argc UNUSED, const char **argv UNUSED)
+static void dump_graph_bloom_filters(struct commit_graph *graph)
+{
+ uint32_t i;
+
+ for (i = 0; i < graph->num_commits + graph->num_commits_in_base; i++) {
+ struct bloom_filter filter = { 0 };
+ size_t j;
+
+ if (load_bloom_filter_from_graph(graph, &filter, i) < 0) {
+ fprintf(stderr, "missing Bloom filter for graph "
+ "position %"PRIu32"\n", i);
+ continue;
+ }
+
+ for (j = 0; j < filter.len; j++)
+ printf("%02x", filter.data[j]);
+ if (filter.len)
+ printf("\n");
+ }
+}
+
+int cmd__read_graph(int argc, const char **argv)
{
struct commit_graph *graph = NULL;
struct object_directory *odb;
+ int ret = 0;
setup_git_directory();
odb = the_repository->objects->odb;
@@ -58,12 +80,24 @@ int cmd__read_graph(int argc UNUSED, const char **argv UNUSED)
prepare_repo_settings(the_repository);
graph = read_commit_graph_one(the_repository, odb);
- if (!graph)
- return 1;
+ if (!graph) {
+ ret = 1;
+ goto done;
+ }
- dump_graph_info(graph);
+ if (argc <= 1)
+ dump_graph_info(graph);
+ else if (!strcmp(argv[1], "bloom-filters"))
+ dump_graph_bloom_filters(graph);
+ else {
+ fprintf(stderr, "unknown sub-command: '%s'\n", argv[1]);
+ ret = 1;
+ }
+done:
UNLEAK(graph);
- return 0;
+ return ret;
}
+
+
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 06/17] bloom.h: make `load_bloom_filter_from_graph()` public
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
Prepare for a future commit to use the load_bloom_filter_from_graph()
function directly to load specific Bloom filters out of the commit-graph
for manual inspection (to be used during tests).
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
bloom.c | 6 +++---
bloom.h | 5 +++++
2 files changed, 8 insertions(+), 3 deletions(-)
diff --git a/bloom.c b/bloom.c
index aef6b5fea2..3e78cfe79d 100644
--- a/bloom.c
+++ b/bloom.c
@@ -29,9 +29,9 @@ static inline unsigned char get_bitmask(uint32_t pos)
return ((unsigned char)1) << (pos & (BITS_PER_WORD - 1));
}
-static int load_bloom_filter_from_graph(struct commit_graph *g,
- struct bloom_filter *filter,
- uint32_t graph_pos)
+int load_bloom_filter_from_graph(struct commit_graph *g,
+ struct bloom_filter *filter,
+ uint32_t graph_pos)
{
uint32_t lex_pos, start_index, end_index;
diff --git a/bloom.h b/bloom.h
index adde6dfe21..1e4f612d2c 100644
--- a/bloom.h
+++ b/bloom.h
@@ -3,6 +3,7 @@
struct commit;
struct repository;
+struct commit_graph;
struct bloom_filter_settings {
/*
@@ -68,6 +69,10 @@ struct bloom_key {
uint32_t *hashes;
};
+int load_bloom_filter_from_graph(struct commit_graph *g,
+ struct bloom_filter *filter,
+ uint32_t graph_pos);
+
/*
* Calculate the murmur3 32-bit hash value for the given data
* using the given seed.
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 03/17] commit-graph: ensure Bloom filters are read with consistent settings
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
The changed-path Bloom filter mechanism is parameterized by a couple of
variables, notably the number of bits per hash (typically "m" in Bloom
filter literature) and the number of hashes themselves (typically "k").
It is critically important that filters are read with the Bloom filter
settings that they were written with. Failing to do so would mean that
each query is liable to compute different fingerprints, meaning that the
filter itself could return a false negative. This goes against a basic
assumption of using Bloom filters (that they may return false positives,
but never false negatives) and can lead to incorrect results.
We have some existing logic to carry forward existing Bloom filter
settings from one layer to the next. In `write_commit_graph()`, we have
something like:
if (!(flags & COMMIT_GRAPH_NO_WRITE_BLOOM_FILTERS)) {
struct commit_graph *g = ctx->r->objects->commit_graph;
/* We have changed-paths already. Keep them in the next graph */
if (g && g->chunk_bloom_data) {
ctx->changed_paths = 1;
ctx->bloom_settings = g->bloom_filter_settings;
}
}
, which drags forward Bloom filter settings across adjacent layers.
This doesn't quite address all cases, however, since it is possible for
intermediate layers to contain no Bloom filters at all. For example,
suppose we have two layers in a commit-graph chain, say, {G1, G2}. If G1
contains Bloom filters, but G2 doesn't, a new G3 (whose base graph is
G2) may be written with arbitrary Bloom filter settings, because we only
check the immediately adjacent layer's settings for compatibility.
This behavior has existed since the introduction of changed-path Bloom
filters. But in practice, this is not such a big deal, since the only
way up until this point to modify the Bloom filter settings at write
time is with the undocumented environment variables:
- GIT_TEST_BLOOM_SETTINGS_BITS_PER_ENTRY
- GIT_TEST_BLOOM_SETTINGS_NUM_HASHES
- GIT_TEST_BLOOM_SETTINGS_MAX_CHANGED_PATHS
(it is still possible to tweak MAX_CHANGED_PATHS between layers, but
this does not affect reads, so is allowed to differ across multiple
graph layers).
But in future commits, we will introduce another parameter to change the
hash algorithm used to compute Bloom fingerprints itself. This will be
exposed via a configuration setting, making this foot-gun easier to use.
To prevent this potential issue, validate that all layers of a split
commit-graph have compatible settings with the newest layer which
contains Bloom filters.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Original-test-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
commit-graph.c | 25 +++++++++++++++++
t/t4216-log-bloom.sh | 64 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 89 insertions(+)
diff --git a/commit-graph.c b/commit-graph.c
index 1a56efcf69..ae0902f7f4 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -498,6 +498,30 @@ static int validate_mixed_generation_chain(struct commit_graph *g)
return 0;
}
+static void validate_mixed_bloom_settings(struct commit_graph *g)
+{
+ struct bloom_filter_settings *settings = NULL;
+ for (; g; g = g->base_graph) {
+ if (!g->bloom_filter_settings)
+ continue;
+ if (!settings) {
+ settings = g->bloom_filter_settings;
+ continue;
+ }
+
+ if (g->bloom_filter_settings->bits_per_entry != settings->bits_per_entry ||
+ g->bloom_filter_settings->num_hashes != settings->num_hashes) {
+ g->chunk_bloom_indexes = NULL;
+ g->chunk_bloom_data = NULL;
+ FREE_AND_NULL(g->bloom_filter_settings);
+
+ warning(_("disabling Bloom filters for commit-graph "
+ "layer '%s' due to incompatible settings"),
+ oid_to_hex(&g->oid));
+ }
+ }
+}
+
static int add_graph_to_chain(struct commit_graph *g,
struct commit_graph *chain,
struct object_id *oids,
@@ -614,6 +638,7 @@ struct commit_graph *load_commit_graph_chain_fd_st(struct repository *r,
}
validate_mixed_generation_chain(graph_chain);
+ validate_mixed_bloom_settings(graph_chain);
free(oids);
fclose(fp);
diff --git a/t/t4216-log-bloom.sh b/t/t4216-log-bloom.sh
index 322640feeb..f49a8f2fbf 100755
--- a/t/t4216-log-bloom.sh
+++ b/t/t4216-log-bloom.sh
@@ -420,4 +420,68 @@ test_expect_success 'Bloom generation backfills empty commits' '
)
'
+graph=.git/objects/info/commit-graph
+graphdir=.git/objects/info/commit-graphs
+chain=$graphdir/commit-graph-chain
+
+test_expect_success 'setup for mixed Bloom setting tests' '
+ repo=mixed-bloom-settings &&
+
+ git init $repo &&
+ for i in one two three
+ do
+ test_commit -C $repo $i file || return 1
+ done
+'
+
+test_expect_success 'split' '
+ # Compute Bloom filters with "unusual" settings.
+ git -C $repo rev-parse one >in &&
+ GIT_TEST_BLOOM_SETTINGS_NUM_HASHES=3 git -C $repo commit-graph write \
+ --stdin-commits --changed-paths --split <in &&
+ layer=$(head -n 1 $repo/$chain) &&
+
+ # A commit-graph layer without Bloom filters "hides" the layers
+ # below ...
+ git -C $repo rev-parse two >in &&
+ git -C $repo commit-graph write --stdin-commits --no-changed-paths \
+ --split=no-merge <in &&
+
+ # Another commit-graph layer that has Bloom filters, but with
+ # standard settings, and is thus incompatible with the base
+ # layer written above.
+ git -C $repo rev-parse HEAD >in &&
+ git -C $repo commit-graph write --stdin-commits --changed-paths \
+ --split=no-merge <in &&
+
+ test_line_count = 3 $repo/$chain &&
+
+ # Ensure that incompatible Bloom filters are ignored.
+ git -C $repo -c core.commitGraph=false log --oneline --no-decorate -- file \
+ >expect 2>err &&
+ git -C $repo log --oneline --no-decorate -- file >actual 2>err &&
+ test_cmp expect actual &&
+ grep "disabling Bloom filters for commit-graph layer .$layer." err
+'
+
+test_expect_success 'merge graph layers with incompatible Bloom settings' '
+ # Ensure that incompatible Bloom filters are ignored when
+ # generating new layers.
+ git -C $repo commit-graph write --reachable --changed-paths 2>err &&
+ grep "disabling Bloom filters for commit-graph layer .$layer." err &&
+
+ test_path_is_file $repo/$graph &&
+ test_dir_is_empty $repo/$graphdir &&
+
+ # ...and merging existing ones.
+ git -C $repo -c core.commitGraph=false log --oneline --no-decorate -- file \
+ >expect 2>err &&
+ GIT_TRACE2_PERF="$(pwd)/trace.perf" \
+ git -C $repo log --oneline --no-decorate -- file >actual 2>err &&
+
+ test_cmp expect actual && cat err &&
+ grep "statistics:{\"filter_not_present\":0" trace.perf &&
+ ! grep "disabling Bloom filters" err
+'
+
test_done
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 05/17] t/helper/test-read-graph.c: extract `dump_graph_info()`
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
Prepare for the 'read-graph' test helper to perform other tasks besides
dumping high-level information about the commit-graph by extracting its
main routine into a separate function.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
t/helper/test-read-graph.c | 31 ++++++++++++++++++-------------
1 file changed, 18 insertions(+), 13 deletions(-)
diff --git a/t/helper/test-read-graph.c b/t/helper/test-read-graph.c
index 8c7a83f578..3375392f6c 100644
--- a/t/helper/test-read-graph.c
+++ b/t/helper/test-read-graph.c
@@ -5,20 +5,8 @@
#include "bloom.h"
#include "setup.h"
-int cmd__read_graph(int argc UNUSED, const char **argv UNUSED)
+static void dump_graph_info(struct commit_graph *graph)
{
- struct commit_graph *graph = NULL;
- struct object_directory *odb;
-
- setup_git_directory();
- odb = the_repository->objects->odb;
-
- prepare_repo_settings(the_repository);
-
- graph = read_commit_graph_one(the_repository, odb);
- if (!graph)
- return 1;
-
printf("header: %08x %d %d %d %d\n",
ntohl(*(uint32_t*)graph->data),
*(unsigned char*)(graph->data + 4),
@@ -57,6 +45,23 @@ int cmd__read_graph(int argc UNUSED, const char **argv UNUSED)
if (graph->topo_levels)
printf(" topo_levels");
printf("\n");
+}
+
+int cmd__read_graph(int argc UNUSED, const char **argv UNUSED)
+{
+ struct commit_graph *graph = NULL;
+ struct object_directory *odb;
+
+ setup_git_directory();
+ odb = the_repository->objects->odb;
+
+ prepare_repo_settings(the_repository);
+
+ graph = read_commit_graph_one(the_repository, odb);
+ if (!graph)
+ return 1;
+
+ dump_graph_info(graph);
UNLEAK(graph);
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 04/17] gitformat-commit-graph: describe version 2 of BDAT
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
From: Jonathan Tan <jonathantanmy@google.com>
The code change to Git to support version 2 will be done in subsequent
commits.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
Documentation/gitformat-commit-graph.txt | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/Documentation/gitformat-commit-graph.txt b/Documentation/gitformat-commit-graph.txt
index 31cad585e2..3e906e8030 100644
--- a/Documentation/gitformat-commit-graph.txt
+++ b/Documentation/gitformat-commit-graph.txt
@@ -142,13 +142,16 @@ All multi-byte numbers are in network byte order.
==== Bloom Filter Data (ID: {'B', 'D', 'A', 'T'}) [Optional]
* It starts with header consisting of three unsigned 32-bit integers:
- - Version of the hash algorithm being used. We currently only support
- value 1 which corresponds to the 32-bit version of the murmur3 hash
+ - Version of the hash algorithm being used. We currently support
+ value 2 which corresponds to the 32-bit version of the murmur3 hash
implemented exactly as described in
https://en.wikipedia.org/wiki/MurmurHash#Algorithm and the double
hashing technique using seed values 0x293ae76f and 0x7e646e2 as
described in https://doi.org/10.1007/978-3-540-30494-4_26 "Bloom Filters
- in Probabilistic Verification"
+ in Probabilistic Verification". Version 1 Bloom filters have a bug that appears
+ when char is signed and the repository has path names that have characters >=
+ 0x80; Git supports reading and writing them, but this ability will be removed
+ in a future version of Git.
- The number of times a path is hashed and hence the number of bit positions
that cumulatively determine whether a file is present in the commit.
- The minimum number of bits 'b' per entry in the Bloom filter. If the filter
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 02/17] revision.c: consult Bloom filters for root commits
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
The commit-graph stores changed-path Bloom filters which represent the
set of paths included in a tree-level diff between a commit's root tree
and that of its parent.
When a commit has no parents, the tree-diff is computed against that
commit's root tree and the empty tree. In other words, every path in
that commit's tree is stored in the Bloom filter (since they all appear
in the diff).
Consult these filters during pathspec-limited traversals in the function
`rev_same_tree_as_empty()`. Doing so yields a performance improvement
where we can avoid enumerating the full set of paths in a parentless
commit's root tree when we know that the path(s) of interest were not
listed in that commit's changed-path Bloom filter.
Suggested-by: SZEDER Gábor <szeder.dev@gmail.com>
Original-patch-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
revision.c | 26 ++++++++++++++++++++++----
t/t4216-log-bloom.sh | 8 ++++++--
2 files changed, 28 insertions(+), 6 deletions(-)
diff --git a/revision.c b/revision.c
index e789834dd1..dae569a547 100644
--- a/revision.c
+++ b/revision.c
@@ -834,17 +834,28 @@ static int rev_compare_tree(struct rev_info *revs,
return tree_difference;
}
-static int rev_same_tree_as_empty(struct rev_info *revs, struct commit *commit)
+static int rev_same_tree_as_empty(struct rev_info *revs, struct commit *commit,
+ int nth_parent)
{
struct tree *t1 = repo_get_commit_tree(the_repository, commit);
+ int bloom_ret = 1;
if (!t1)
return 0;
+ if (nth_parent == 1 && revs->bloom_keys_nr) {
+ bloom_ret = check_maybe_different_in_bloom_filter(revs, commit);
+ if (!bloom_ret)
+ return 1;
+ }
+
tree_difference = REV_TREE_SAME;
revs->pruning.flags.has_changes = 0;
diff_tree_oid(NULL, &t1->object.oid, "", &revs->pruning);
+ if (bloom_ret == 1 && tree_difference == REV_TREE_SAME)
+ count_bloom_filter_false_positive++;
+
return tree_difference == REV_TREE_SAME;
}
@@ -882,7 +893,7 @@ static int compact_treesame(struct rev_info *revs, struct commit *commit, unsign
if (nth_parent != 0)
die("compact_treesame %u", nth_parent);
old_same = !!(commit->object.flags & TREESAME);
- if (rev_same_tree_as_empty(revs, commit))
+ if (rev_same_tree_as_empty(revs, commit, nth_parent))
commit->object.flags |= TREESAME;
else
commit->object.flags &= ~TREESAME;
@@ -978,7 +989,14 @@ static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
return;
if (!commit->parents) {
- if (rev_same_tree_as_empty(revs, commit))
+ /*
+ * Pretend as if we are comparing ourselves to the
+ * (non-existent) first parent of this commit object. Even
+ * though no such parent exists, its changed-path Bloom filter
+ * (if one exists) is relative to the empty tree, using Bloom
+ * filters is allowed here.
+ */
+ if (rev_same_tree_as_empty(revs, commit, 1))
commit->object.flags |= TREESAME;
return;
}
@@ -1059,7 +1077,7 @@ static void try_to_simplify_commit(struct rev_info *revs, struct commit *commit)
case REV_TREE_NEW:
if (revs->remove_empty_trees &&
- rev_same_tree_as_empty(revs, p)) {
+ rev_same_tree_as_empty(revs, p, nth_parent)) {
/* We are adding all the specified
* paths from this parent, so the
* history beyond this parent is not
diff --git a/t/t4216-log-bloom.sh b/t/t4216-log-bloom.sh
index 487fc3d6b9..322640feeb 100755
--- a/t/t4216-log-bloom.sh
+++ b/t/t4216-log-bloom.sh
@@ -87,7 +87,11 @@ test_bloom_filters_not_used () {
# if the Bloom filter system is initialized, ensure that no
# filters were used
data="statistics:{"
- data="$data\"filter_not_present\":0,"
+ # unusable filters (e.g., those computed with a
+ # different value of commitGraph.changedPathsVersion)
+ # are counted in the filter_not_present bucket, so any
+ # value is OK there.
+ data="$data\"filter_not_present\":[0-9][0-9]*,"
data="$data\"maybe\":0,"
data="$data\"definitely_not\":0,"
data="$data\"false_positive\":0}"
@@ -174,7 +178,7 @@ test_expect_success 'setup - add commit-graph to the chain with Bloom filters' '
test_bloom_filters_used_when_some_filters_are_missing () {
log_args=$1
- bloom_trace_prefix="statistics:{\"filter_not_present\":3,\"maybe\":6,\"definitely_not\":9"
+ bloom_trace_prefix="statistics:{\"filter_not_present\":3,\"maybe\":6,\"definitely_not\":10"
setup "$log_args" &&
grep -q "$bloom_trace_prefix" "$TRASH_DIRECTORY/trace.perf" &&
test_cmp log_wo_bloom log_w_bloom
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 01/17] t/t4216-log-bloom.sh: harden `test_bloom_filters_not_used()`
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1696969994.git.me@ttaylorr.com>
The existing implementation of test_bloom_filters_not_used() asserts
that the Bloom filter sub-system has not been initialized at all, by
checking for the absence of any data from it from trace2.
In the following commit, it will become possible to load Bloom filters
without using them (e.g., because `commitGraph.changedPathVersion` is
incompatible with the hash version with which the commit-graph's Bloom
filters were written).
When this is the case, it's possible to initialize the Bloom filter
sub-system, while still not using any Bloom filters. When this is the
case, check that the data dump from the Bloom sub-system is all zeros,
indicating that no filters were used.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
t/t4216-log-bloom.sh | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/t/t4216-log-bloom.sh b/t/t4216-log-bloom.sh
index fa9d32facf..487fc3d6b9 100755
--- a/t/t4216-log-bloom.sh
+++ b/t/t4216-log-bloom.sh
@@ -81,7 +81,19 @@ test_bloom_filters_used () {
test_bloom_filters_not_used () {
log_args=$1
setup "$log_args" &&
- ! grep -q "statistics:{\"filter_not_present\":" "$TRASH_DIRECTORY/trace.perf" &&
+
+ if grep -q "statistics:{\"filter_not_present\":" "$TRASH_DIRECTORY/trace.perf"
+ then
+ # if the Bloom filter system is initialized, ensure that no
+ # filters were used
+ data="statistics:{"
+ data="$data\"filter_not_present\":0,"
+ data="$data\"maybe\":0,"
+ data="$data\"definitely_not\":0,"
+ data="$data\"false_positive\":0}"
+
+ grep -q "$data" "$TRASH_DIRECTORY/trace.perf"
+ fi &&
test_cmp log_wo_bloom log_w_bloom
}
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply related
* [PATCH v3 00/17] bloom: changed-path Bloom filters v2 (& sundries)
From: Taylor Blau @ 2023-10-10 20:33 UTC (permalink / raw)
To: git; +Cc: Jonathan Tan, Junio C Hamano, Jeff King, SZEDER Gábor
In-Reply-To: <cover.1692654233.git.me@ttaylorr.com>
(Rebased onto the tip of 'master', which is 3a06386e31 (The fifteenth
batch, 2023-10-04), at the time of writing).
This series is a reroll of the combined efforts of [1] and [2] to
introduce the v2 changed-path Bloom filters, which fixes a bug in our
existing implementation of murmur3 paths with non-ASCII characters (when
the "char" type is signed).
In large part, this is the same as the previous round. But this round
includes some extra bits that address issues pointed out by SZEDER
Gábor, which are:
- not reading Bloom filters for root commits
- corrupting Bloom filter reads by tweaking the filter settings
between layers.
These issues were discussed in (among other places) [3], and [4],
respectively.
Thanks to Jonathan, Peff, and SZEDER who have helped a great deal in
assembling these patches. As usual, a range-diff is included below.
Thanks in advance for your
review!
[1]: https://lore.kernel.org/git/cover.1684790529.git.jonathantanmy@google.com/
[2]: https://lore.kernel.org/git/cover.1691426160.git.me@ttaylorr.com/
[3]: https://public-inbox.org/git/20201015132147.GB24954@szeder.dev/
[4]: https://lore.kernel.org/git/20230830200218.GA5147@szeder.dev/
Jonathan Tan (4):
gitformat-commit-graph: describe version 2 of BDAT
t4216: test changed path filters with high bit paths
repo-settings: introduce commitgraph.changedPathsVersion
commit-graph: new filter ver. that fixes murmur3
Taylor Blau (13):
t/t4216-log-bloom.sh: harden `test_bloom_filters_not_used()`
revision.c: consult Bloom filters for root commits
commit-graph: ensure Bloom filters are read with consistent settings
t/helper/test-read-graph.c: extract `dump_graph_info()`
bloom.h: make `load_bloom_filter_from_graph()` public
t/helper/test-read-graph: implement `bloom-filters` mode
bloom: annotate filters with hash version
bloom: prepare to discard incompatible Bloom filters
commit-graph.c: unconditionally load Bloom filters
commit-graph: drop unnecessary `graph_read_bloom_data_context`
object.h: fix mis-aligned flag bits table
commit-graph: reuse existing Bloom filters where possible
bloom: introduce `deinit_bloom_filters()`
Documentation/config/commitgraph.txt | 26 ++-
Documentation/gitformat-commit-graph.txt | 9 +-
bloom.c | 208 ++++++++++++++++-
bloom.h | 38 +++-
commit-graph.c | 61 ++++-
object.h | 3 +-
oss-fuzz/fuzz-commit-graph.c | 2 +-
repo-settings.c | 6 +-
repository.h | 2 +-
revision.c | 26 ++-
t/helper/test-bloom.c | 9 +-
t/helper/test-read-graph.c | 67 ++++--
t/t0095-bloom.sh | 8 +
t/t4216-log-bloom.sh | 272 ++++++++++++++++++++++-
14 files changed, 682 insertions(+), 55 deletions(-)
Range-diff against v2:
10: 002a06d1e9 ! 1: fe671d616c t/t4216-log-bloom.sh: harden `test_bloom_filters_not_used()`
@@ Commit message
indicating that no filters were used.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
- Signed-off-by: Junio C Hamano <gitster@pobox.com>
- Signed-off-by: Taylor Blau <me@ttaylorr.com>
## t/t4216-log-bloom.sh ##
@@ t/t4216-log-bloom.sh: test_bloom_filters_used () {
-: ---------- > 2: 7d0fa93543 revision.c: consult Bloom filters for root commits
-: ---------- > 3: 2ecc0a2d58 commit-graph: ensure Bloom filters are read with consistent settings
1: 5fa681b58e ! 4: 17703ed89a gitformat-commit-graph: describe version 2 of BDAT
@@ Commit message
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
- Signed-off-by: Junio C Hamano <gitster@pobox.com>
- Signed-off-by: Taylor Blau <me@ttaylorr.com>
## Documentation/gitformat-commit-graph.txt ##
@@ Documentation/gitformat-commit-graph.txt: All multi-byte numbers are in network byte order.
2: 623d840575 ! 5: 94552abf45 t/helper/test-read-graph.c: extract `dump_graph_info()`
@@ Commit message
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
- Signed-off-by: Junio C Hamano <gitster@pobox.com>
- Signed-off-by: Taylor Blau <me@ttaylorr.com>
## t/helper/test-read-graph.c ##
@@
3: bc9d77ae60 ! 6: 3d81efa27b bloom.h: make `load_bloom_filter_from_graph()` public
@@ Commit message
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
- Signed-off-by: Junio C Hamano <gitster@pobox.com>
- Signed-off-by: Taylor Blau <me@ttaylorr.com>
## bloom.c ##
@@ bloom.c: static inline unsigned char get_bitmask(uint32_t pos)
4: ac7008aed3 ! 7: d23cd89037 t/helper/test-read-graph: implement `bloom-filters` mode
@@ Commit message
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
- Signed-off-by: Junio C Hamano <gitster@pobox.com>
- Signed-off-by: Taylor Blau <me@ttaylorr.com>
## t/helper/test-read-graph.c ##
@@ t/helper/test-read-graph.c: static void dump_graph_info(struct commit_graph *graph)
@@ t/helper/test-read-graph.c: int cmd__read_graph(int argc UNUSED, const char **ar
- return 0;
+ return ret;
}
++
++
5: 71755ba856 ! 8: cba766f224 t4216: test changed path filters with high bit paths
@@ Commit message
Signed-off-by: Taylor Blau <me@ttaylorr.com>
## t/t4216-log-bloom.sh ##
-@@ t/t4216-log-bloom.sh: test_expect_success 'Bloom generation backfills empty commits' '
- )
+@@ t/t4216-log-bloom.sh: test_expect_success 'merge graph layers with incompatible Bloom settings' '
+ ! grep "disabling Bloom filters" err
'
+get_first_changed_path_filter () {
6: 9768d92c0f ! 9: a08a961f41 repo-settings: introduce commitgraph.changedPathsVersion
@@ Commit message
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
- Signed-off-by: Junio C Hamano <gitster@pobox.com>
- Signed-off-by: Taylor Blau <me@ttaylorr.com>
## Documentation/config/commitgraph.txt ##
@@ Documentation/config/commitgraph.txt: commitGraph.maxNewFilters::
7: f911b4bfab = 10: 61d44519a5 commit-graph: new filter ver. that fixes murmur3
8: 35009900df ! 11: a8c10f8de8 bloom: annotate filters with hash version
@@ Commit message
Bloom filter.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
- Signed-off-by: Junio C Hamano <gitster@pobox.com>
- Signed-off-by: Taylor Blau <me@ttaylorr.com>
## bloom.c ##
@@ bloom.c: int load_bloom_filter_from_graph(struct commit_graph *g,
9: 138bc16905 ! 12: 2ba10a4b4b bloom: prepare to discard incompatible Bloom filters
@@ Commit message
`get_or_compute_bloom_filter()`.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
- Signed-off-by: Junio C Hamano <gitster@pobox.com>
- Signed-off-by: Taylor Blau <me@ttaylorr.com>
## bloom.c ##
@@ bloom.c: static void init_truncated_large_filter(struct bloom_filter *filter,
11: 2437e62813 ! 13: 09d8669c3a commit-graph.c: unconditionally load Bloom filters
@@ Commit message
either "1" or "2".
Signed-off-by: Taylor Blau <me@ttaylorr.com>
- Signed-off-by: Junio C Hamano <gitster@pobox.com>
- Signed-off-by: Taylor Blau <me@ttaylorr.com>
## commit-graph.c ##
@@ commit-graph.c: static int graph_read_bloom_data(const unsigned char *chunk_start,
12: fe8fb2f5fe ! 14: 0d4f9dc4ee commit-graph: drop unnecessary `graph_read_bloom_data_context`
@@ Commit message
Noticed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
- Signed-off-by: Junio C Hamano <gitster@pobox.com>
- Signed-off-by: Taylor Blau <me@ttaylorr.com>
## commit-graph.c ##
@@ commit-graph.c: static int graph_read_oid_lookup(const unsigned char *chunk_start,
13: 825af91e11 ! 15: 1f7f27bc47 object.h: fix mis-aligned flag bits table
@@ Commit message
Bit position 23 is one column too far to the left.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
- Signed-off-by: Junio C Hamano <gitster@pobox.com>
- Signed-off-by: Taylor Blau <me@ttaylorr.com>
## object.h ##
@@ object.h: void object_array_init(struct object_array *array);
14: 593b317192 ! 16: abbef95ae8 commit-graph: reuse existing Bloom filters where possible
@@ Commit message
commits by their generation number.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
- Signed-off-by: Junio C Hamano <gitster@pobox.com>
- Signed-off-by: Taylor Blau <me@ttaylorr.com>
## bloom.c ##
@@
15: 8bf2c9cf98 = 17: ca362408d5 bloom: introduce `deinit_bloom_filters()`
--
2.42.0.342.g8bb3a896ee
^ permalink raw reply
page: next (older) | prev (newer) | latest
- recent:[subjects (threaded)|topics (new)|topics (active)]
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox