From: David Ahern <dsahern@gmail.com>
To: Rabin Vincent <rabin@rab.in>, Yunlong Song <yunlong.song@huawei.com>
Cc: a.p.zijlstra@chello.nl, paulus@samba.org, mingo@redhat.com,
Arnaldo Carvalho de Melo <acme@kernel.org>,
linux-kernel@vger.kernel.org, wangnan0@huawei.com
Subject: Re: [Question] How does perf still record the stack of a specified pid even when that process is interrupted and CPU is scheduled to other process
Date: Tue, 05 May 2015 16:24:54 -0600 [thread overview]
Message-ID: <55494336.4060709@gmail.com> (raw)
In-Reply-To: <20150505215328.GA3397@debian>
On 5/5/15 3:53 PM, Rabin Vincent wrote:
> The commands above will identify the sys_write which takes time but only
> provide the stacktrace at the entry and exit of the syscall, but this do
> not show why the process blocked or what it did inside the system call.
>
> So a way to get what is required for the use case would be to make the
> following changes to the above sequence:
>
> (1) include the sched:* events when perf trace record is run
>
> (2) around the time of interest, look at the kernel stack st the sched:switch
> events between the entry and the exit. This will show what the process was
> waiting for when it when it blocked. The stacktraces at the
> stat_runtime events in the process may also be useful to understand what
> was going on.
agreed.
next prev parent reply other threads:[~2015-05-05 22:24 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-24 13:31 [Question] How does perf still record the stack of a specified pid even when that process is interrupted and CPU is scheduled to other process Yunlong Song
2015-04-24 13:49 ` Yunlong Song
2015-04-25 14:03 ` Yunlong Song
2015-04-24 13:49 ` David Ahern
2015-04-24 13:56 ` Yunlong Song
2015-04-24 13:58 ` David Ahern
2015-04-25 14:05 ` Yunlong Song
2015-04-25 15:53 ` David Ahern
2015-05-05 21:53 ` Rabin Vincent
2015-05-05 22:24 ` David Ahern [this message]
2015-05-06 4:13 ` Yunlong Song
2015-05-06 4:10 ` Yunlong Song
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