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From: Andy Lutomirski <luto@amacapital.net>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Arnaldo Carvalho de Melo <acme@infradead.org>,
	clark@redhat.com, Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Ingo Molnar <mingo@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH] perf: add 'perf bench syscall'
Date: Tue, 21 Jun 2016 09:31:26 -0700	[thread overview]
Message-ID: <CALCETrUsS9cpyrh4rr6U8u2Jfeef1S6sjYU7uqbV_3+A+MTRoA@mail.gmail.com> (raw)
In-Reply-To: <20160621145539.byehondkdw6jhbha@treble>

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

      reply	other threads:[~2016-06-21 16:31 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-01  2:12 [PATCH 0/4 v3] sched,time: reduce nohz_full syscall overhead 40% riel
2016-02-01  2:12 ` [PATCH 1/4] sched,time: remove non-power-of-two divides from __acct_update_integrals riel
2016-02-01  4:46   ` kbuild test robot
2016-02-01  8:37   ` Thomas Gleixner
2016-02-01  9:22     ` Peter Zijlstra
2016-02-01  9:31       ` Thomas Gleixner
2016-02-01 13:44       ` Rik van Riel
2016-02-01 13:51         ` Peter Zijlstra
2016-02-01  2:12 ` [PATCH 2/4] acct,time: change indentation in __acct_update_integrals riel
2016-02-01  2:12 ` [PATCH 3/4] time,acct: drop irq save & restore from __acct_update_integrals riel
2016-02-01  9:28   ` Peter Zijlstra
2016-02-01 19:22     ` Rik van Riel
2016-02-01  2:12 ` [PATCH 4/4] sched,time: only call account_{user,sys,guest,idle}_time once a jiffy riel
2016-02-01  9:29   ` Peter Zijlstra
2016-02-01 19:23     ` Rik van Riel
2016-02-01  7:41 ` [PATCH] perf tooling: Add 'perf bench syscall' benchmark Ingo Molnar
2016-02-01  7:48   ` [PATCH] perf tooling: Simplify 'perf bench syscall' Ingo Molnar
2016-02-01 15:41   ` [PATCH] perf tooling: Add 'perf bench syscall' benchmark Andy Lutomirski
2016-02-03 10:22     ` Ingo Molnar
2016-06-20 18:00       ` [PATCH] perf: add 'perf bench syscall' Josh Poimboeuf
2016-06-20 19:16         ` Andy Lutomirski
2016-06-21 14:55           ` Josh Poimboeuf
2016-06-21 16:31             ` Andy Lutomirski [this message]

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