From: Peter Zijlstra <a.p.zijlstra@chello•nl>
To: Michael Ellerman <michael@ellerman•id.au>
Cc: Michael Neuling <mikey@neuling•org>,
Frederic Weisbecker <fweisbec@gmail•com>,
linux-kernel@vger•kernel.org, linuxppc-dev@ozlabs•org,
K Prasad <prasad@linux•vnet.ibm.com>,
Ingo Molnar <mingo@kernel•org>
Subject: Re: powerpc/perf: hw breakpoints return ENOSPC
Date: Thu, 16 Aug 2012 16:15:02 +0200 [thread overview]
Message-ID: <1345126502.29668.36.camel@twins> (raw)
In-Reply-To: <1345125747.20062.12.camel@concordia>
On Fri, 2012-08-17 at 00:02 +1000, Michael Ellerman wrote:
> You do want to guarantee that the task will always be subject to the
> breakpoint, even if it moves cpus. So is there any way to guarantee that
> other than reserving a breakpoint slot on every cpu ahead of time?=20
That's not how regular perf works.. regular perf can overload hw
resources at will and stuff is strictly per-cpu.
So the regular perf record has perf_event_attr::inherit enabled by
default, this will result in it creating a per-task-per-cpu event for
each cpu and this will succeed because there's no strict reservation to
avoid/detect starvation against perf_event_attr::pinned events.
For regular (!pinned) events, we'll RR the created events on the
available hardware resources.
HWBP does things completely different and reserves a slot over all CPUs
for everything, thus stuff completely falls apart.
next prev parent reply other threads:[~2012-08-16 14:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-16 4:23 powerpc/perf: hw breakpoints return ENOSPC Michael Neuling
2012-08-16 7:40 ` Peter Zijlstra
2012-08-16 11:17 ` Michael Neuling
2012-08-16 11:44 ` Peter Zijlstra
2012-08-16 14:02 ` Michael Ellerman
2012-08-16 14:15 ` Peter Zijlstra [this message]
2012-08-17 1:20 ` Michael Ellerman
2012-08-16 23:34 ` Michael Neuling
2012-08-17 16:15 ` Frederic Weisbecker
2012-08-17 21:58 ` Michael Neuling
2012-09-25 7:10 ` Michael Neuling
2012-09-27 15:23 ` Frederic Weisbecker
2012-09-27 1:02 ` Jovi Zhang
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