Re: [PATCH] perf: add 'perf bench syscall'

From	Andy Lutomirski <luto@amacapital.net>
Newsgroups	linux.kernel
Subject	Re: [PATCH] perf: add 'perf bench syscall'
Date	2016-06-21 18:40 +0200
Message-ID	<rMwSt-8eX-1@gated-at.bofh.it> (permalink)
References	(2 earlier) <qXoTO-4WL-41@gated-at.bofh.it> <qY2Rd-H6-27@gated-at.bofh.it> <rMbO1-3aM-3@gated-at.bofh.it> <rMd3r-3UC-21@gated-at.bofh.it> <rMvto-7tu-21@gated-at.bofh.it>
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On Jun 21, 2016 7:55 AM, "Josh Poimboeuf" <jpoimboe@redhat.com> wrote:
>
> On Mon, Jun 20, 2016 at 12:16:22PM -0700, Andy Lutomirski wrote:
> > On Mon, Jun 20, 2016 at 11:00 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > >
> > > From: Josh Poimboeuf <jpoimboe@redhat.com>
> > > Subject: [PATCH] perf: add 'perf bench syscall'
> > >
> > > Add a basic 'perf bench syscall' benchmark which does a getppid() system
> > > call in a tight loop.
> > >
> >
> > My one suggestion would be to use a different syscall than getppid(),
> > as getppid() can have unusual performance characteristics on kernels
> > with pid namespaces enabled.  I'm a fan of prctl(-1, 0, 0, 0, 0).
>
> Hm, can you elaborate on the unusual performance characteristics of
> getppid()?  The code seems pretty minimal.

task_this_vnr -> pid_vnr -> pid_nr_ns

There's probably something better than prctl, though.

--Andy

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[PATCH] perf: add 'perf bench syscall' Josh Poimboeuf <jpoimboe@redhat.com> - 2016-06-20 20:10 +0200
  Re: [PATCH] perf: add 'perf bench syscall' Andy Lutomirski <luto@amacapital.net> - 2016-06-20 21:30 +0200
    Re: [PATCH] perf: add 'perf bench syscall' Josh Poimboeuf <jpoimboe@redhat.com> - 2016-06-21 17:10 +0200
      Re: [PATCH] perf: add 'perf bench syscall' Andy Lutomirski <luto@amacapital.net> - 2016-06-21 18:40 +0200

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