From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Vince Weaver <vweaver1@eecs.utk.edu>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Stephane Eranian <eranian@gmail.com>,
Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: perf: is PERF_COUNT_SW_CONTEXT_SWITCHES a kernel or user event?
Date: Mon, 27 Jun 2011 12:43:23 +0200 [thread overview]
Message-ID: <1309171403.6701.77.camel@twins> (raw)
In-Reply-To: <alpine.DEB.2.00.1106241658420.23095@cl320.eecs.utk.edu>
On Fri, 2011-06-24 at 17:03 -0400, Vince Weaver wrote:
> Hello
>
> the commit included in 2.6.34:
> perf: Use hot regs with software sched switch/migrate events
> e49a5bd38159dfb1928fd25b173bc9de4bbadb21
>
> Changes the behavior of the PERF_COUNT_SW_CONTEXT_SWITCHES
> counter.
>
> Before 2.6.34 all of the PERF_COUNT_SW_CONTEXT_SWITCHES events were
> counted as happening in userspace (they show up in "perf stat -e cs:u")
> but after the commit they always happen in kernelspace ("perf stat -e
> cs:k").
>
> Was this intended behavior?
> I'm writing a validation test for this and want to make sure I get it
> right.
>
> This can be confusing if your tool defaults to userspace only counts (PAPI
> does this).
hurm, difficult case, like the changelog explains the previous behaviour
wasn't ideal either. Seems like we want somewhat of a middle ground
there, but I'm not quite sure how to make that happen.
Let me ponder things for a bit.
next prev parent reply other threads:[~2011-06-27 10:45 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-24 21:03 perf: is PERF_COUNT_SW_CONTEXT_SWITCHES a kernel or user event? Vince Weaver
2011-06-27 10:43 ` Peter Zijlstra [this message]
2011-06-27 18:59 ` Frederic Weisbecker
2011-06-28 17:30 ` Vince Weaver
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