From: Arnaldo Carvalho de Melo <acme@kernel.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>, Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Ian Rogers <irogers@google.com>,
linux-perf-users <linux-perf-users@vger.kernel.org>,
Song Liu <songliubraving@fb.com>, bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH 0/4] perf lock contention: Improve call stack handling (v1)
Date: Wed, 21 Sep 2022 15:09:47 +0100 [thread overview]
Message-ID: <YysbKwpO9XLfHM90@kernel.org> (raw)
In-Reply-To: <CAM9d7ch7owDKkn9a89qkZ-KpSf02+OVJd01_76xMadA+vv3owQ@mail.gmail.com>
Em Tue, Sep 20, 2022 at 02:04:47PM -0700, Namhyung Kim escreveu:
> On Tue, Sep 20, 2022 at 1:22 PM Arnaldo Carvalho de Melo
> <acme@kernel.org> wrote:
> >
> > Em Thu, Sep 08, 2022 at 04:44:15PM -0700, Namhyung Kim escreveu:
> > > Hi Arnaldo,
> > >
> > > On Thu, Sep 8, 2022 at 11:43 AM Arnaldo Carvalho de Melo
> > > <acme@kernel.org> wrote:
> > > >
> > > > Em Wed, Sep 07, 2022 at 11:37:50PM -0700, Namhyung Kim escreveu:
> > > > > Hello,
> > > > >
> > > > > I found that call stack from the lock tracepoint (using bpf_get_stackid)
> > > > > can be different on each configuration. For example it's very different
> > > > > when I run it on a VM than on a real machine.
> > > > >
> > > > > The perf lock contention relies on the stack trace to get the lock
> > > > > caller names, this kind of difference can be annoying. Ideally we could
> > > > > skip stack trace entries for internal BPF or lock functions and get the
> > > > > correct caller, but it's not the case as of today. Currently it's hard
> > > > > coded to control the behavior of stack traces for the lock contention
> > > > > tracepoints.
> > > > >
> > > > > To handle those differences, add two new options to control the number of
> > > > > stack entries and how many it skips. The default value worked well on
> > > > > my VM setup, but I had to use --stack-skip=5 on real machines.
> > > > >
> > > > > You can get it from 'perf/lock-stack-v1' branch in
> > > > >
> > > > > git://git.kernel.org/pub/scm/linux/kernel/git/namhyung/linux-perf.git
> > > >
> > > > This clashed with a patch you Acked earlier, so lets see if someone has
> > > > extra review comments and a v2 become needed for other reason, when you
> > > > can refresh it, ok?
> > >
> > > Sounds good!
> >
> > Have you resubmitted this? /me goes on the backlog...
>
> Yep :)
>
> https://lore.kernel.org/r/20220912055314.744552-1-namhyung@kernel.org
It applies now, testing :-)
- Arnaldo
prev parent reply other threads:[~2022-09-21 14:10 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-08 6:37 [PATCH 0/4] perf lock contention: Improve call stack handling (v1) Namhyung Kim
2022-09-08 6:37 ` [PATCH 1/4] perf lock contention: Factor out get_symbol_name_offset() Namhyung Kim
2022-09-08 6:37 ` [PATCH 2/4] perf lock contention: Show full callstack with -v option Namhyung Kim
2022-09-08 6:37 ` [PATCH 3/4] perf lock contention: Allow to change stack depth and skip Namhyung Kim
2022-09-08 6:37 ` [PATCH 4/4] perf lock contention: Skip stack trace from BPF Namhyung Kim
2022-09-08 18:43 ` [PATCH 0/4] perf lock contention: Improve call stack handling (v1) Arnaldo Carvalho de Melo
2022-09-08 23:44 ` Namhyung Kim
2022-09-20 20:22 ` Arnaldo Carvalho de Melo
2022-09-20 21:04 ` Namhyung Kim
2022-09-21 14:09 ` Arnaldo Carvalho de Melo [this message]
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