From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Mark Wielaard <mjw@redhat.com>
Cc: Kui-Feng Lee <kuifeng@fb.com>,
dwarves@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH dwarves v4 3/4] pahole: Use per-thread btf instances to avoid mutex locking.
Date: Fri, 28 Jan 2022 16:50:48 -0300 [thread overview]
Message-ID: <YfRJGJ35SQCy+98H@kernel.org> (raw)
In-Reply-To: <YfL8kjM30uHN3qxs@kernel.org>
Em Thu, Jan 27, 2022 at 05:12:02PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Wed, Jan 26, 2022 at 11:58:27AM -0800, Andrii Nakryiko escreveu:
> > On Wed, Jan 26, 2022 at 11:21 AM Kui-Feng Lee <kuifeng@fb.com> wrote:
> > > Create an instance of btf for each worker thread, and add type info to
> > > the local btf instance in the steal-function of pahole without mutex
> > > acquiring. Once finished with all worker threads, merge all
> > > per-thread btf instances to the primary btf instance.
> > There are still unnecessary casts and missing {} in the else branch,
> > but I'll let Arnaldo decide or fix it up.
So its just one unneeded cast as thr_data here is just a 'void *':
diff --git a/pahole.c b/pahole.c
index 8c0a982f05c9ae3d..39e18804100dbfda 100644
--- a/pahole.c
+++ b/pahole.c
@@ -2924,7 +2924,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu,
* avoids copying the data collected by the first thread.
*/
if (thr_data) {
- struct thread_data *thread = (struct thread_data *)thr_data;
+ struct thread_data *thread = thr_data;
if (thread->encoder == NULL) {
thread->encoder =
This other is needed as it is a "void **":
@@ -2832,7 +2832,7 @@ static int pahole_thread_exit(struct conf_load *conf, void *thr_data)
static int pahole_threads_collect(struct conf_load *conf, int nr_threads, void **thr_data,
int error)
{
- struct thread_data **threads = (struct thread_data **)thr_data;
+ struct thread_data **threads = thr_data;
int i;
int err = 0;
Removing it:
/var/home/acme/git/pahole/pahole.c: In function ‘pahole_threads_collect’:
/var/home/acme/git/pahole/pahole.c:2835:40: warning: initialization of ‘struct thread_data **’ from incompatible pointer type ‘void **’ [-Wincompatible-pointer-types]
2835 | struct thread_data **threads = thr_data;
| ^~~~~~~~
And I did some more profiling, now the focus should go to elfutils:
⬢[acme@toolbox pahole]$ perf report --no-children -s dso --call-graph none 2> /dev/null | head -20
# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 0
#
# Samples: 27K of event 'cycles:u'
# Event count (approx.): 27956766207
#
# Overhead Shared Object
# ........ ...................
#
46.70% libdwarves.so.1.0.0
39.84% libdw-0.186.so
9.70% libc-2.33.so
2.14% libpthread-2.33.so
1.47% [unknown]
0.09% ld-2.33.so
0.06% libelf-0.186.so
0.00% libcrypto.so.1.1.1l
0.00% libk5crypto.so.3.1
⬢[acme@toolbox pahole]$
$ perf report -g graph,0.5,2 --stdio --no-children -s dso --dso libdw-0.186.so
# To display the perf.data header info, please use --header/--header-only options.
#
# dso: libdw-0.186.so
#
# Total Lost Samples: 0
#
# Samples: 27K of event 'cycles:u'
# Event count (approx.): 27956766207
#
# Overhead Shared Object
# ........ ..............
#
39.84% libdw-0.186.so
|
|--25.66%--__libdw_find_attr
| |
| |--20.96%--__dwarf_attr_internal (inlined)
| | |
| | |--10.94%--attr_numeric
| | | |
| | | |--9.96%--die__process_class
| | | | __die__process_tag
| | | | die__process_unit
| | | | die__process
| | | | dwarf_cus__create_and_process_cu
| | | | dwarf_cus__process_cu_thread
| | | | start_thread
| | | | __GI___clone (inlined)
| | | |
| | | --0.61%--type__init
| | | __die__process_tag
| | | die__process_unit
| | | die__process
| | | dwarf_cus__create_and_process_cu
| | | dwarf_cus__process_cu_thread
| | | start_thread
| | | __GI___clone (inlined)
| | |
| | |--5.43%--attr_type
| | | |
| | | --4.94%--tag__init
| | | |
| | | |--2.60%--die__process_class
| | | | __die__process_tag
| | | | die__process_unit
| | | | die__process
| | | | dwarf_cus__create_and_process_cu
| | | | dwarf_cus__process_cu_thread
| | | | start_thread
| | | | __GI___clone (inlined)
| | | |
| | | |--0.99%--__die__process_tag
| | | | |
| | | | --0.98%--die__process_unit
| | | | die__process
| | | | dwarf_cus__create_and_process_cu
| | | | dwarf_cus__process_cu_thread
| | | | start_thread
| | | | __GI___clone (inlined)
| |
| |--4.01%--__dwarf_siblingof_internal (inlined)
| | |
| | |--1.41%--die__process_class
| | | __die__process_tag
| | | die__process_unit
| | | die__process
| | | dwarf_cus__create_and_process_cu
| | | dwarf_cus__process_cu_thread
| | | start_thread
| | | __GI___clone (inlined)
| | |
| | |--1.02%--die__process
| | | dwarf_cus__create_and_process_cu
| | | dwarf_cus__process_cu_thread
| | | start_thread
| | | __GI___clone (inlined)
|
|--2.38%--__libdw_form_val_compute_len
| __libdw_find_attr
| |
| --1.86%--__dwarf_attr_internal (inlined)
| |
| |--0.94%--attr_numeric
| | |
| | --0.83%--die__process_class
| | __die__process_tag
| | die__process_unit
| | die__process
| | dwarf_cus__create_and_process_cu
| | dwarf_cus__process_cu_thread
| | start_thread
| | __GI___clone (inlined)
| |
| --0.56%--attr_type
| |
| --0.53%--tag__init
#
# (Tip: If you have debuginfo enabled, try: perf report -s sym,srcline)
#
This find_attr thing needs improvements, its a linear search AFAIK, some
hashtable could do wonders, I guess.
Mark, was this considered at some point?
⬢[acme@toolbox pahole]$ rpm -q elfutils-libs
elfutils-libs-0.186-1.fc34.x86_64
Andrii https://github.com/libbpf/libbpf/actions/workflows/pahole.yml is
in failure mode for 3 days, and only yesterday I pushed these changes,
seems unrelated to pahole:
Tests exit status: 1
Test Results:
bpftool: PASS
test_progs: FAIL (returned 1)
test_progs-no_alu32: FAIL (returned 1)
test_verifier: PASS
shutdown: CLEAN
Error: Process completed with exit code 1.
Can you please check?
- Arnaldo
next prev parent reply other threads:[~2022-01-28 19:52 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-26 19:20 [PATCH dwarves v4 0/4] Parallelize BTF type info generating of pahole Kui-Feng Lee
2022-01-26 19:20 ` [PATCH dwarves v4 1/4] dwarf_loader: Receive per-thread data on worker threads Kui-Feng Lee
2022-01-26 19:55 ` Andrii Nakryiko
2022-01-26 20:14 ` Kui-Feng Lee
2022-01-27 10:05 ` Arnaldo Carvalho de Melo
2022-03-08 23:45 ` Andrii Nakryiko
2022-03-09 19:24 ` Arnaldo Carvalho de Melo
2022-03-10 0:14 ` Andrii Nakryiko
2022-03-10 0:18 ` Andrii Nakryiko
2022-03-21 19:06 ` Kui-Feng Lee
2022-03-21 21:08 ` Arnaldo Carvalho de Melo
2022-03-14 15:38 ` Arnaldo Carvalho de Melo
2022-03-14 15:43 ` Arnaldo Carvalho de Melo
2022-01-26 19:20 ` [PATCH dwarves v4 2/4] dwarf_loader: Prepare and pass per-thread data to " Kui-Feng Lee
2022-01-26 19:55 ` Andrii Nakryiko
2022-01-26 19:20 ` [PATCH dwarves v4 3/4] pahole: Use per-thread btf instances to avoid mutex locking Kui-Feng Lee
2022-01-26 19:58 ` Andrii Nakryiko
2022-01-26 20:57 ` Kui-Feng Lee
2022-01-27 10:05 ` Arnaldo Carvalho de Melo
2022-01-27 20:12 ` Arnaldo Carvalho de Melo
2022-01-28 19:50 ` Arnaldo Carvalho de Melo [this message]
2022-02-01 6:56 ` Andrii Nakryiko
2022-02-02 0:16 ` Arnaldo Carvalho de Melo
2022-01-26 19:20 ` [PATCH dwarves v4 4/4] libbpf: Update libbpf to a new revision Kui-Feng Lee
2022-01-26 19:59 ` Andrii Nakryiko
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