[PATCH 0/4] perf lock contention: Improve aggr x filter combination (v1)

Namhyung Kim
2023-02-02T05:05:04Z

Hello,

The callstack filter can be useful to debug lock issues but it has a
limitation that it only works with caller aggregation mode (which is the
default setting). IOW it cannot filter by callstack when showing tasks
or lock addresses/names.

But sometimes users want to use the filter for other aggregation mode.
Like "show me lock addresses/names from this caller only" or "show me
tasks having these callers".

When it's using tracepoint events from the data file, the situation is
good since the tracepoints have all the necessary info. But when using
BPF it needs to extend the key of lock stat BPF map to have more than
one info like 'pid + stack_id' or 'lock_addr + stack_id'. As callstack
filter works in userspace, it should save the both info.

With this change we can now use the -S/--callstack-filter with the
-t/--threads option or -l/--lock-addr option. It's also possible to use
it with other filter options.

The following example shows the top 5 tasks that have contention
somewhere in the epoll handling.

$ sudo perf lock con -abt -S epoll -E5 -- sleep 1
contended total wait max wait avg wait pid comm

2 58.64 us 32.38 us 29.32 us 1514752 Chrome_IOThread
3 29.31 us 12.65 us 9.77 us 3773 Xorg
1 17.45 us 17.45 us 17.45 us 1514906 Chrome_ChildIOT
1 15.41 us 15.41 us 15.41 us 1515382 Chrome_ChildIOT
1 12.52 us 12.52 us 12.52 us 293878 IPC I/O Parent

You get get the code at 'perf/lock-filter-v1' branch in

git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git

Thanks,
Namhyung

Namhyung Kim (4):
perf lock contention: Factor out lock_contention_get_name()
perf lock contention: Use lock_stat_find{,new}
perf lock contention: Support filters for different aggregation
perf test: Add more test cases for perf lock contention

tools/perf/builtin-lock.c | 79 ++++----
tools/perf/tests/shell/lock_contention.sh | 66 ++++++-
tools/perf/util/bpf_lock_contention.c | 178 +++++++++++-------
.../perf/util/bpf_skel/lock_contention.bpf.c | 15 +-
tools/perf/util/bpf_skel/lock_data.h | 4 +-
tools/perf/util/lock-contention.h | 5 +
6 files changed, 234 insertions(+), 113 deletions(-)

base-commit: 7cfa9f5e440054db7c7e28e83a045d36993ff958
--
2.39.1.456.gfc5497dd1b-goog