linux-kernel - Re: [PATCH v2 0/3] perf lock contention: Improve aggr x filter combination

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Date:   Fri, 3 Feb 2023 17:12:47 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     jolsa@...nel.org, peterz@...radead.org, mingo@...hat.com,
        irogers@...gle.com, linux-kernel@...r.kernel.org,
        adrian.hunter@...el.com, linux-perf-users@...r.kernel.org,
        song@...nel.org, haoluo@...gle.com, bpf@...r.kernel.org,
        juri.lelli@...hat.com
Subject: Re: [PATCH v2 0/3] perf lock contention: Improve aggr x filter
 combination

Em Thu, Feb 02, 2023 at 06:13:21PM -0800, Namhyung Kim escreveu:
> 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.

Thanks, applied.

- Arnaldo

 
> 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 (3):
>   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
> 
>  tools/perf/builtin-lock.c                     |  79 ++++----
>  tools/perf/util/Build                         |   5 +-
>  tools/perf/util/bpf_lock_contention.c         | 180 +++++++++++-------
>  .../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, 178 insertions(+), 110 deletions(-)
> 
> -- 
> 2.39.1.519.gcb327c4b5f-goog
> 

-- 

- Arnaldo