* [PATCH/RFC v3 1/2] Optimised, faster, more effective symlink/directory detection
2009-01-07 13:24 [PATCH/RFC v3 0/2] git checkout: optimise away lots of lstat() calls Kjetil Barvik
@ 2009-01-07 13:24 ` Kjetil Barvik
2009-01-09 10:20 ` Pete Harlan
2009-01-07 13:24 ` [PATCH/RFC v3 2/2] create_directories() inside entry.c: only check each directory once! Kjetil Barvik
1 sibling, 1 reply; 4+ messages in thread
From: Kjetil Barvik @ 2009-01-07 13:24 UTC (permalink / raw)
To: git; +Cc: Linus Torvalds, Kjetil Barvik
Changes includes the following:
- The cache functionality is more effective. Previously when A/B/C/D
was in the cache and A/B/C/E/file.c was called for, there was no
match at all from the cache. Now we use the fact that the paths
"A", "A/B" and "A/B/C" is already tested, and we only need to do an
lstat() call on "A/B/C/E".
- We only cache/store the last path regardless of it's type. Since the
cache functionality is always used with alphabetically sorted names
(at least it seams so for me), there is no need to store both the
last symlink-leading path and the last real-directory path. Note
that if the cache is not called with (mostly) alphabetically sorted
names, neither the old, nor this new one, would be very effective.
- We also can cache the fact that a directory does not exist.
Previously we could end up doing lots of lstat() calls for a removed
directory which previously contained lots of files. Since we
already have simplified the cache functionality and only store the
last path (see above), this new functionality was easy to add.
- Previously, when symlink A/B/C/S was cached/stored in the
symlink-leading path, and A/B/C/file.c was called for, it was not
easy to use the fact that we already known that the paths "A", "A/B"
and "A/B/C" is real directories. Since we now only store one single
path (the last one), we also get similar logic for free regarding
the new "non-exsisting-directory-cache".
- Avoid copying the first path components of the name 2 zillions times
when we tests new path components. Since we always cache/store the
last path, we can copy each component as we test those directly into
the cache. Previously we ended up doing a memcpy() for the full
path/name right before each lstat() call, and when updating the
cache for each time we have tested an new path component.
- We also use less memory, that is PATH_MAX bytes less memory on the
stack and PATH_MAX bytes less memory on the heap.
- Introduce a 3rd argument, 'unsigned int track_flags', to the
cache-test function, check_lstat_cache(). This new argument can be
used to tell the cache functionality which types of directories
should be cached.
- Also introduce a 'void clear_lstat_cache(void)' function, which
should be used to clean the cache before usage. If for instance,
you have changed the types of directories which should be cached,
the cache could contain a path which was not wanted.
Signed-off-by: Kjetil Barvik <barvik@broadpark.no>
---
:100644 100644 719de8b... 870961e... M builtin-add.c
:100644 100644 a8f75ed... d3d001a... M builtin-apply.c
:100644 100644 5604977... 8907219... M builtin-update-index.c
:100644 100644 231c06d... 768ba38... M cache.h
:100644 100644 ae96c64... c9caa0e... M diff-lib.c
:100644 100644 5a5e781... 2f025c8... M symlinks.c
:100644 100644 54f301d... 28e2759... M unpack-trees.c
builtin-add.c | 1 +
builtin-apply.c | 1 +
builtin-update-index.c | 1 +
cache.h | 22 ++++++++-
diff-lib.c | 1 +
symlinks.c | 123 +++++++++++++++++++++++++++++++-----------------
unpack-trees.c | 5 +-
7 files changed, 107 insertions(+), 47 deletions(-)
diff --git a/builtin-add.c b/builtin-add.c
index 719de8b0f2d2d831f326d948aa18700e5c474950..870961e8ca4e3d6f9333020083d0a232bccd542c 100644
--- a/builtin-add.c
+++ b/builtin-add.c
@@ -225,6 +225,7 @@ int cmd_add(int argc, const char **argv, const char *prefix)
argc = parse_options(argc, argv, builtin_add_options,
builtin_add_usage, 0);
+ clear_symlink_cache();
if (patch_interactive)
add_interactive = 1;
if (add_interactive)
diff --git a/builtin-apply.c b/builtin-apply.c
index a8f75ed3ed411d8cf7a3ec9dfefef7407c50f447..d3d001a96be6e502d6338af4467f7c313370d78e 100644
--- a/builtin-apply.c
+++ b/builtin-apply.c
@@ -3154,6 +3154,7 @@ int cmd_apply(int argc, const char **argv, const char *unused_prefix)
if (apply_default_whitespace)
parse_whitespace_option(apply_default_whitespace);
+ clear_symlink_cache();
for (i = 1; i < argc; i++) {
const char *arg = argv[i];
char *end;
diff --git a/builtin-update-index.c b/builtin-update-index.c
index 560497750586ec61be4e34de6dedd9c307129817..8907219fb9cb438113e29ee17854edb5dd4baa4d 100644
--- a/builtin-update-index.c
+++ b/builtin-update-index.c
@@ -581,6 +581,7 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
if (entries < 0)
die("cache corrupted");
+ clear_symlink_cache();
for (i = 1 ; i < argc; i++) {
const char *path = argv[i];
const char *p;
diff --git a/cache.h b/cache.h
index 231c06d7726b575f6e522d5b0c0fe43557e8c651..768ba3825f3015828381490b0c387177a4f71578 100644
--- a/cache.h
+++ b/cache.h
@@ -719,7 +719,27 @@ struct checkout {
};
extern int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *topath);
-extern int has_symlink_leading_path(int len, const char *name);
+
+#define LSTAT_DIR (1u << 0)
+#define LSTAT_NOENT (1u << 1)
+#define LSTAT_SYMLINK (1u << 2)
+#define LSTAT_LSTATERR (1u << 3)
+#define LSTAT_ERR (1u << 4)
+extern unsigned int check_lstat_cache(int len, const char *name,
+ unsigned int track_flags);
+extern void clear_lstat_cache(void);
+static inline unsigned int has_symlink_leading_path(int len, const char *name)
+{
+ return check_lstat_cache(len, name, LSTAT_SYMLINK|LSTAT_DIR) &
+ LSTAT_SYMLINK;
+}
+#define clear_symlink_cache() clear_lstat_cache()
+static inline unsigned int has_symlink_or_noent_leading_path(int len, const char *name)
+{
+ return check_lstat_cache(len, name, LSTAT_SYMLINK|LSTAT_NOENT|LSTAT_DIR) &
+ (LSTAT_SYMLINK|LSTAT_NOENT);
+}
+#define clear_symlink_or_noent_cache() clear_lstat_cache()
extern struct alternate_object_database {
struct alternate_object_database *next;
diff --git a/diff-lib.c b/diff-lib.c
index ae96c64ca209f4df9008198e8a04b160bed618c7..c9caa0e6ef0f4a8ee8b850869ef6d0f52b712385 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -69,6 +69,7 @@ int run_diff_files(struct rev_info *revs, unsigned int option)
diff_unmerged_stage = 2;
entries = active_nr;
symcache[0] = '\0';
+ clear_symlink_cache();
for (i = 0; i < entries; i++) {
struct stat st;
unsigned int oldmode, newmode;
diff --git a/symlinks.c b/symlinks.c
index 5a5e781a15d7d9cb60797958433eca896b31ec85..2f025c87b0be0e713af7b1400e71284a22c25e9f 100644
--- a/symlinks.c
+++ b/symlinks.c
@@ -1,64 +1,99 @@
#include "cache.h"
-struct pathname {
- int len;
- char path[PATH_MAX];
-};
+static char cache_path[PATH_MAX];
+static int cache_len = 0;
+static unsigned int cache_flags = 0;
-/* Return matching pathname prefix length, or zero if not matching */
-static inline int match_pathname(int len, const char *name, struct pathname *match)
+static inline int
+greatest_common_path_cache_prefix(int len, const char *name)
{
- int match_len = match->len;
- return (len > match_len &&
- name[match_len] == '/' &&
- !memcmp(name, match->path, match_len)) ? match_len : 0;
-}
+ int max_len, match_len = 0, i = 0;
-static inline void set_pathname(int len, const char *name, struct pathname *match)
-{
- if (len < PATH_MAX) {
- match->len = len;
- memcpy(match->path, name, len);
- match->path[len] = 0;
+ max_len = len < cache_len ? len : cache_len;
+ while (i < max_len && name[i] == cache_path[i]) {
+ if (name[i] == '/') match_len = i;
+ i++;
}
+ if (i == cache_len && len > cache_len && name[cache_len] == '/')
+ match_len = cache_len;
+ return match_len;
}
-int has_symlink_leading_path(int len, const char *name)
+/*
+ * Check if name 'name' of length 'len' has a symlink leading
+ * component, or if the directory exists and is real, or not.
+ *
+ * To speed up the check, some information is allowed to be cached.
+ * This is indicated by the 'track_flags' argument.
+ */
+unsigned int
+check_lstat_cache(int len, const char *name, unsigned int track_flags)
{
- static struct pathname link, nonlink;
- char path[PATH_MAX];
+ int match_len, last_slash, max_len;
+ unsigned int match_flags, ret_flags, save_flags;
struct stat st;
- char *sp;
- int known_dir;
- /*
- * See if the last known symlink cache matches.
+ /* Check if match from the cache for 2 "excluding" path types.
*/
- if (match_pathname(len, name, &link))
- return 1;
+ match_len = last_slash =
+ greatest_common_path_cache_prefix(len, name);
+ match_flags =
+ cache_flags & track_flags & (LSTAT_NOENT|LSTAT_SYMLINK);
+ if (match_flags && match_len == cache_len)
+ return match_flags;
- /*
- * Get rid of the last known directory part
+ /* Okay, no match from the cache so far, so now we have to
+ * check the rest of the path components.
*/
- known_dir = match_pathname(len, name, &nonlink);
-
- while ((sp = strchr(name + known_dir + 1, '/')) != NULL) {
- int thislen = sp - name ;
- memcpy(path, name, thislen);
- path[thislen] = 0;
+ ret_flags = LSTAT_DIR;
+ max_len = len < PATH_MAX ? len : PATH_MAX;
+ while (match_len < max_len) {
+ do {
+ cache_path[match_len] = name[match_len];
+ match_len++;
+ } while (match_len < max_len && name[match_len] != '/');
+ if (match_len >= max_len)
+ break;
+ last_slash = match_len;
+ cache_path[last_slash] = '\0';
- if (lstat(path, &st))
- return 0;
- if (S_ISDIR(st.st_mode)) {
- set_pathname(thislen, path, &nonlink);
- known_dir = thislen;
+ if (lstat(cache_path, &st)) {
+ ret_flags = LSTAT_LSTATERR;
+ if (errno == ENOENT)
+ ret_flags |= LSTAT_NOENT;
+ } else if (S_ISDIR(st.st_mode)) {
continue;
- }
- if (S_ISLNK(st.st_mode)) {
- set_pathname(thislen, path, &link);
- return 1;
+ } else if (S_ISLNK(st.st_mode)) {
+ ret_flags = LSTAT_SYMLINK;
+ } else {
+ ret_flags = LSTAT_ERR;
}
break;
}
- return 0;
+
+ /* At the end update the cache. Note that max 3 different
+ * path types can be cached for the moment!
+ */
+ save_flags = ret_flags & track_flags &
+ (LSTAT_NOENT|LSTAT_SYMLINK|LSTAT_DIR);
+ if (save_flags && last_slash > 0 && last_slash < PATH_MAX) {
+ cache_path[last_slash] = '\0';
+ cache_len = last_slash;
+ cache_flags = save_flags;
+ } else {
+ clear_lstat_cache();
+ }
+ return ret_flags;
+}
+
+/*
+ * Before usage of the check_lstat_cache() function one should call
+ * clear_lstat_cache() (at an appropriate place) to make sure that the
+ * cache is clean.
+ */
+void clear_lstat_cache(void)
+{
+ cache_path[0] = '\0';
+ cache_len = 0;
+ cache_flags = 0;
}
diff --git a/unpack-trees.c b/unpack-trees.c
index 54f301da67be879c80426bc21776427fdd38c02e..28e275981a21b033459ef9c7e420cce4bf7e5513 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -61,7 +61,7 @@ static void unlink_entry(struct cache_entry *ce)
char *cp, *prev;
char *name = ce->name;
- if (has_symlink_leading_path(ce_namelen(ce), ce->name))
+ if (has_symlink_or_noent_leading_path(ce_namelen(ce), ce->name))
return;
if (unlink(name))
return;
@@ -105,6 +105,7 @@ static int check_updates(struct unpack_trees_options *o)
cnt = 0;
}
+ clear_symlink_or_noent_cache();
for (i = 0; i < index->cache_nr; i++) {
struct cache_entry *ce = index->cache[i];
@@ -584,7 +585,7 @@ static int verify_absent(struct cache_entry *ce, const char *action,
if (o->index_only || o->reset || !o->update)
return 0;
- if (has_symlink_leading_path(ce_namelen(ce), ce->name))
+ if (has_symlink_or_noent_leading_path(ce_namelen(ce), ce->name))
return 0;
if (!lstat(ce->name, &st)) {
--
1.6.1.rc1.49.g7f705
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH/RFC v3 2/2] create_directories() inside entry.c: only check each directory once!
2009-01-07 13:24 [PATCH/RFC v3 0/2] git checkout: optimise away lots of lstat() calls Kjetil Barvik
2009-01-07 13:24 ` [PATCH/RFC v3 1/2] Optimised, faster, more effective symlink/directory detection Kjetil Barvik
@ 2009-01-07 13:24 ` Kjetil Barvik
1 sibling, 0 replies; 4+ messages in thread
From: Kjetil Barvik @ 2009-01-07 13:24 UTC (permalink / raw)
To: git; +Cc: Linus Torvalds, Kjetil Barvik
When we do an 'git checkout' after some time we end up in the
'checkout_entry()' function inside entry.c, and from here we call the
'create_directories()' function to make sure the all the directories
exists for the possible new file or entry.
The 'create_directories()' function happily started to check that all
path component exists. This resulted in tons and tons of calls to
lstat() or stat() when we checkout files nested deep inside a
directory.
We try to avoid this by remembering the last checked and possible
newly created directory.
Signed-off-by: Kjetil Barvik <barvik@broadpark.no>
---
:100644 100644 768ba38... ec1297f... M cache.h
:100644 100644 aa2ee46... 36d6f98... M entry.c
:100644 100644 28e2759... 0a03e65... M unpack-trees.c
cache.h | 1 +
entry.c | 82 +++++++++++++++++++++++++++++++++++++++++++------------
unpack-trees.c | 1 +
3 files changed, 66 insertions(+), 18 deletions(-)
diff --git a/cache.h b/cache.h
index 768ba3825f3015828381490b0c387177a4f71578..ec1297ff5621cc9eb7fce51cc025f18a030ac9ea 100644
--- a/cache.h
+++ b/cache.h
@@ -718,6 +718,7 @@ struct checkout {
refresh_cache:1;
};
+extern void clear_created_dirs_cache(void);
extern int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *topath);
#define LSTAT_DIR (1u << 0)
diff --git a/entry.c b/entry.c
index aa2ee46a84033585d8e07a585610c5a697af82c2..36d6f98c1f59a86a5e9c117e1181c1169208168f 100644
--- a/entry.c
+++ b/entry.c
@@ -1,33 +1,67 @@
#include "cache.h"
#include "blob.h"
-static void create_directories(const char *path, const struct checkout *state)
+static char dirs_path[PATH_MAX];
+static int dirs_len = 0;
+
+static inline int
+greatest_common_created_dirs_prefix(int len, const char *name)
{
- int len = strlen(path);
- char *buf = xmalloc(len + 1);
- const char *slash = path;
+ int max_len, match_len = 0, i = 0;
- while ((slash = strchr(slash+1, '/')) != NULL) {
- struct stat st;
- int stat_status;
+ max_len = len < dirs_len ? len : dirs_len;
+ while (i < max_len && name[i] == dirs_path[i]) {
+ if (name[i] == '/') match_len = i;
+ i++;
+ }
+ if (i == dirs_len && len > dirs_len && name[dirs_len] == '/')
+ match_len = dirs_len;
+ return match_len;
+}
- len = slash - path;
- memcpy(buf, path, len);
- buf[len] = 0;
+void clear_created_dirs_cache(void)
+{
+ dirs_path[0] = '\0';
+ dirs_len = 0;
+}
- if (len <= state->base_dir_len)
+static void
+create_directories(int len, const char *path, const struct checkout *state)
+{
+ int i, max_len, last_slash, stat_status;
+ struct stat st;
+
+ /* Check the cache for previously checked or created
+ * directories (and components) within this function. There
+ * is no need to check or re-create directory components more
+ * than once!
+ */
+ max_len = len < PATH_MAX ? len : PATH_MAX;
+ i = last_slash = greatest_common_created_dirs_prefix(max_len, path);
+
+ while (i < max_len) {
+ do {
+ dirs_path[i] = path[i];
+ i++;
+ } while (i < max_len && path[i] != '/');
+ if (i >= max_len)
+ break;
+ last_slash = i;
+ dirs_path[last_slash] = '\0';
+
+ if (last_slash <= state->base_dir_len)
/*
* checkout-index --prefix=<dir>; <dir> is
* allowed to be a symlink to an existing
* directory.
*/
- stat_status = stat(buf, &st);
+ stat_status = stat(dirs_path, &st);
else
/*
* if there currently is a symlink, we would
* want to replace it with a real directory.
*/
- stat_status = lstat(buf, &st);
+ stat_status = lstat(dirs_path, &st);
if (!stat_status && S_ISDIR(st.st_mode))
continue; /* ok, it is already a directory. */
@@ -38,14 +72,20 @@ static void create_directories(const char *path, const struct checkout *state)
* error codepath; we do not care, as we unlink and
* mkdir again in such a case.
*/
- if (mkdir(buf, 0777)) {
+ if (mkdir(dirs_path, 0777)) {
if (errno == EEXIST && state->force &&
- !unlink(buf) && !mkdir(buf, 0777))
+ !unlink(dirs_path) && !mkdir(dirs_path, 0777))
continue;
- die("cannot create directory at %s", buf);
+ die("cannot create directory at %s", dirs_path);
}
}
- free(buf);
+ /* Update the cache of already created/checked directories */
+ if (last_slash > 0 && last_slash < PATH_MAX) {
+ dirs_path[last_slash] = '\0';
+ dirs_len = last_slash;
+ } else {
+ clear_created_dirs_cache();
+ }
}
static void remove_subtree(const char *path)
@@ -55,6 +95,11 @@ static void remove_subtree(const char *path)
char pathbuf[PATH_MAX];
char *name;
+ /* To be utterly safe we invalidate the cache of the
+ * previously created directories.
+ */
+ clear_created_dirs_cache();
+
if (!dir)
die("cannot opendir %s (%s)", path, strerror(errno));
strcpy(pathbuf, path);
@@ -201,6 +246,7 @@ int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *t
memcpy(path, state->base_dir, len);
strcpy(path + len, ce->name);
+ len += ce_namelen(ce);
if (!lstat(path, &st)) {
unsigned changed = ce_match_stat(ce, &st, CE_MATCH_IGNORE_VALID);
@@ -229,6 +275,6 @@ int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *t
return error("unable to unlink old '%s' (%s)", path, strerror(errno));
} else if (state->not_new)
return 0;
- create_directories(path, state);
+ create_directories(len, path, state);
return write_entry(ce, path, state, 0);
}
diff --git a/unpack-trees.c b/unpack-trees.c
index 28e275981a21b033459ef9c7e420cce4bf7e5513..0a03e65f9c9d869ab2d8b3c337f032ff2b8e7b2f 100644
--- a/unpack-trees.c
+++ b/unpack-trees.c
@@ -119,6 +119,7 @@ static int check_updates(struct unpack_trees_options *o)
}
}
+ clear_created_dirs_cache();
for (i = 0; i < index->cache_nr; i++) {
struct cache_entry *ce = index->cache[i];
--
1.6.1.rc1.49.g7f705
^ permalink raw reply related [flat|nested] 4+ messages in thread