From: Frederic Weisbecker <fweisbec@gmail.com>
To: Anton Blanchard <anton@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@elte.hu>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mundt <lethal@linux-sh.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] perf: Fix inconsistency between IP and callchain sampling
Date: Thu, 21 Jan 2010 14:20:18 +0100 [thread overview]
Message-ID: <20100121132014.GH5017@nowhere> (raw)
In-Reply-To: <20100118054707.GT12666@kryten>
On Mon, Jan 18, 2010 at 04:47:07PM +1100, Anton Blanchard wrote:
>
> When running perf across all cpus with backtracing (-a -g), sometimes we
> get samples without associated backtraces:
>
> 23.44% init [kernel] [k] restore
> 11.46% init eeba0c [k] 0x00000000eeba0c
> 6.77% swapper [kernel] [k] .perf_ctx_adjust_freq
> 5.73% init [kernel] [k] .__trace_hcall_entry
> 4.69% perf libc-2.9.so [.] 0x0000000006bb8c
> |
> |--11.11%-- 0xfffa941bbbc
>
> It turns out the backtrace code has a check for the idle task and the IP
> sampling does not. This creates problems when profiling an interrupt
> heavy workload (in my case 10Gbit ethernet) since we get no backtraces
> for interrupts received while idle (ie most of the workload).
>
> Right now x86 and sh check that current is not NULL, which should never
> happen so remove that too.
>
> Signed-off-by: Anton Blanchard <anton@samba.org>
I'm queuing it. Thanks.
next prev parent reply other threads:[~2010-01-21 13:20 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-18 5:47 [PATCH] perf: Fix inconsistency between IP and callchain sampling Anton Blanchard
2010-01-18 10:43 ` Frederic Weisbecker
2010-01-22 2:04 ` Anton Blanchard
2010-01-22 7:25 ` Ingo Molnar
2010-01-21 13:20 ` Frederic Weisbecker [this message]
2010-01-29 9:24 ` [tip:perf/core] " tip-bot for Anton Blanchard
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