From: David Ahern <dsahern@gmail.com>
To: Brendan Gregg <brendan.d.gregg@gmail.com>,
linux-perf-users@vger.kernel.org
Subject: Re: Fwd: filtering perf itself
Date: Mon, 07 Jul 2014 12:44:41 -0600 [thread overview]
Message-ID: <53BAEA99.7050602@gmail.com> (raw)
In-Reply-To: <CAE40pdePzcfHfZzuOC6DyFc2H7DQMZ_JzADvx_guDS+Eg4SJtw@mail.gmail.com>
On 7/7/14, 12:38 PM, Brendan Gregg wrote:
> G'Day perf users,
>
> Is there a way to filter perf from tracing itself?
>
> Here's an idle system:
>
> # ./perf record -e syscalls:sys_enter_read -a sleep 5
> [ perf record: Woken up 2 times to write data ]
> [ perf record: Captured and wrote 0.569 MB perf.data (~24864 samples) ]
> # ./perf record -e syscalls:sys_enter_write -a sleep 5
> [ perf record: Woken up 0 times to write data ]
> [ perf record: Captured and wrote 150.381 MB perf.data (~6570251 samples) ]
>
> Note the disparity. perf is capturing its own writes, creating a feedback loop.
Not a filter, but works around the problem using mmap'ed output file:
https://github.com/dsahern/linux/commit/ae2d7010256f5a5b247fb4df9f764a911a34a2f3
David
next prev parent reply other threads:[~2014-07-07 18:44 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAE40pdeACbvYJN0BMh9edGGLvdpV_H1Kn5ccgBh7GFuDHiuWGQ@mail.gmail.com>
2014-07-07 18:38 ` Fwd: filtering perf itself Brendan Gregg
2014-07-07 18:44 ` David Ahern [this message]
2014-07-07 19:00 ` Brendan Gregg
2014-07-07 19:16 ` Brendan Gregg
2014-07-07 19:31 ` Brendan Gregg
2014-07-08 19:10 ` William Cohen
2014-07-09 19:27 ` Brendan Gregg
2014-07-08 20:45 ` Andi Kleen
2014-07-09 19:47 ` Brendan Gregg
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