From: Jiri Olsa <jolsa@redhat.com>
To: Sujith Manoharan <sujith@msujith.org>
Cc: linux-perf-users@vger.kernel.org
Subject: Re: perf lock usage
Date: Tue, 28 Jan 2014 10:35:42 +0100 [thread overview]
Message-ID: <20140128093542.GD1229@krava.brq.redhat.com> (raw)
In-Reply-To: <21216.48020.60857.22056@gargle.gargle.HOWL>
On Thu, Jan 23, 2014 at 12:19:56PM +0530, Sujith Manoharan wrote:
> Hi,
>
> I am trying to use perf lock and am not sure if
> the results are correct (the bad rate is 98 %).
>
> Is this expected behavior ?
some of the kernel lock types do not follow the:
acquire
contended
acuired
release
lock state machine, like rcu or spin locks.. and thats what
caused most of the bad rates in my tests.
I was recently working on some changes for lock tracing,
what stats are you interested in?
jirka
>
> root@linux-test ~# perf --version
> perf version 3.12.0
>
> root@linux-test ~# perf lock record cat /etc/issue
> Arch Linux \r (\l)
>
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.356 MB perf.data (~15533 samples) ]
> root@linux-test ~# perf lock report
> Name acquired contended total wait (ns) max wait (ns) min wait (ns)
>
> &cpuctx_lock 0 0 0 0 0
> &sig->cred_guard... 0 0 0 0 0
>
> === output for debug===
>
> bad: 153, total: 155
> bad rate: 98.709677 %
> histogram of events caused bad sequence
> acquire: 1
> acquired: 0
> contended: 0
> release: 152
>
> I am using the wireless-testing kernel:
> root@linux-test ~# uname -a
> Linux linux-test 3.13.0-wl-debug #197 SMP PREEMPT Tue Jan 21 03:19:43 IST 2014 x86_64 GNU/Linux
>
> lockdep is enabled:
> root@linux-test ~# zgrep -i lockdep /proc/config.gz
> CONFIG_LOCKDEP_SUPPORT=y
> CONFIG_LOCKDEP=y
> # CONFIG_DEBUG_LOCKDEP is not set
>
>
> Sujith
> --
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next prev parent reply other threads:[~2014-01-28 9:35 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-23 6:49 perf lock usage Sujith Manoharan
2014-01-23 12:36 ` Frederic Weisbecker
2014-01-23 12:37 ` Sujith Manoharan
2014-01-28 9:35 ` Jiri Olsa [this message]
2014-01-29 13:53 ` Sujith Manoharan
2014-01-30 10:33 ` Jiri Olsa
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