Re: [PATCH 0/4] perf lock contention: Improve call stack handling (v1)

[Namhyung Kim]

Hi Arnaldo,

On Thu, Sep 8, 2022 at 11:43 AM Arnaldo Carvalho de Melo
<acme@xxxxxxxxxx> 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!

Thanks,
Namhyung