linux-kernel - Re: [PATCH v1 2/6] perf trace: Ignore thread hashing in summary

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Date: Wed, 14 Feb 2024 13:42:09 -0800
From: Ian Rogers <irogers@...gle.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Oliver Upton <oliver.upton@...ux.dev>, 
	Yang Jihong <yangjihong1@...wei.com>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v1 2/6] perf trace: Ignore thread hashing in summary

On Wed, Feb 14, 2024 at 1:36 PM Ian Rogers <irogers@...gle.com> wrote:
>
> On Wed, Feb 14, 2024 at 1:15 PM Ian Rogers <irogers@...gle.com> wrote:
> >
> > On Wed, Feb 14, 2024 at 10:27 AM Ian Rogers <irogers@...gle.com> wrote:
> > >
> > > On Wed, Feb 14, 2024 at 9:25 AM Arnaldo Carvalho de Melo
> > > <acme@...nel.org> wrote:
> > > >
> > > > On Tue, Feb 13, 2024 at 10:37:04PM -0800, Ian Rogers wrote:
> > > > > Commit 91e467bc568f ("perf machine: Use hashtable for machine
> > > > > threads") made the iteration of thread tids unordered. The perf trace
> > > > > --summary output sorts and prints each hash bucket, rather than all
> > > > > threads globally. Change this behavior by turn all threads into a
> > > > > list, sort the list by number of trace events then by tids, finally
> > > > > print the list. This also allows the rbtree in threads to be not
> > > > > accessed outside of machine.
> > > >
> > > > Can you please provide a refresh of the output that is changed by your patch?
> > >
> > > Hmm.. looks like perf trace record has broken and doesn't produce
> > > output in newer perfs. It works on 6.5 and so a bisect is necessary.
> >
> > Bisect result:
> > ```
> > 9925495d96efc14d885ba66c5696f664fe0e663c is the first bad commit
> > commit 9925495d96efc14d885ba66c5696f664fe0e663c
> > Author: Ian Rogers <irogers@...gle.com>
> > Date:   Thu Sep 14 14:19:45 2023 -0700
> >
> >    perf build: Default BUILD_BPF_SKEL, warn/disable for missing deps
> > ...
> > https://lore.kernel.org/r/20230914211948.814999-3-irogers@google.com
> > ```
> >
> > Now to do the bisect with BUILD_BPF_SKEL=1 on each make.
>
> This looks better (how could I be at fault :-) ):
> ```
> 1836480429d173c01664a633b61e525b13d41a2a is the first bad commit
> commit 1836480429d173c01664a633b61e525b13d41a2a
> Author: Arnaldo Carvalho de Melo <acme@...hat.com>
> Date:   Wed Aug 16 13:53:26 2023 -0300
>
>    perf bpf_skel augmented_raw_syscalls: Cap the socklen parameter
> using &= sizeof(saddr)
> ...
>    Cc: Adrian Hunter <adrian.hunter@...el.com>
>    Cc: Ian Rogers <irogers@...gle.com>
>    Cc: Jiri Olsa <jolsa@...nel.org>
>    Cc: Namhyung Kim <namhyung@...nel.org>
>    Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> ```
> No LKML link.

Hmm.. basically that change fixed the BPF program to verify and so the
problem has been long standing with the BPF code. Maybe perf trace
record never worked with BPF.

Thanks,
Ian