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From: Mark Rutland <mark.rutland@arm.com>
To: skannan@codeaurora.org
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	avilaj@codeaurora.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 2/2] perf/core: Add support for PMUs that can be read from any CPU
Date: Tue, 27 Feb 2018 11:52:25 +0000	[thread overview]
Message-ID: <20180227115224.rmtfy4eif3g4hmmr@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <7cab1b91545e81e4b6b09e85c2f81d7e@codeaurora.org>

On Mon, Feb 26, 2018 at 05:53:57PM -0800, skannan@codeaurora.org wrote:
> On 2018-02-24 00:41, Peter Zijlstra wrote:
> > On Fri, Feb 23, 2018 at 04:19:38PM -0800, Saravana Kannan wrote:
> > > Some PMUs events can be read from any CPU. So allow the PMU to mark
> > > events as such. For these events, we don't need to reject reads or
> > > make smp calls to the event's CPU and cause unnecessary wake ups.
> > > 
> > > Good examples of such events would be events from caches shared across
> > > all CPUs.
> > 
> > So why would the existing ACTIVE_PKG not work for you? Because clearly
> > your example does not cross a package.
> 
> Because based on testing it on hardware, it looks like the two clusters in
> an ARM DynamIQ design are not considered part of the same "package". 

I don't think we should consider the topology masks at all for system
PMU affinity. Due to the number of ways these can be integrated, and the
lack of a standard(ish) topology across arm platforms.

IIUC, there's ongoing work to try to clean that up, but that won't give
us anything meaningful for PMU affinity.

If we need a mask, that should be something the FW description of the
PMU provides, and the PMU driver provides to the core code.

Thanks,
Mark.

WARNING: multiple messages have this Message-ID (diff)
From: mark.rutland@arm.com (Mark Rutland)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v1 2/2] perf/core: Add support for PMUs that can be read from any CPU
Date: Tue, 27 Feb 2018 11:52:25 +0000	[thread overview]
Message-ID: <20180227115224.rmtfy4eif3g4hmmr@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <7cab1b91545e81e4b6b09e85c2f81d7e@codeaurora.org>

On Mon, Feb 26, 2018 at 05:53:57PM -0800, skannan at codeaurora.org wrote:
> On 2018-02-24 00:41, Peter Zijlstra wrote:
> > On Fri, Feb 23, 2018 at 04:19:38PM -0800, Saravana Kannan wrote:
> > > Some PMUs events can be read from any CPU. So allow the PMU to mark
> > > events as such. For these events, we don't need to reject reads or
> > > make smp calls to the event's CPU and cause unnecessary wake ups.
> > > 
> > > Good examples of such events would be events from caches shared across
> > > all CPUs.
> > 
> > So why would the existing ACTIVE_PKG not work for you? Because clearly
> > your example does not cross a package.
> 
> Because based on testing it on hardware, it looks like the two clusters in
> an ARM DynamIQ design are not considered part of the same "package". 

I don't think we should consider the topology masks at all for system
PMU affinity. Due to the number of ways these can be integrated, and the
lack of a standard(ish) topology across arm platforms.

IIUC, there's ongoing work to try to clean that up, but that won't give
us anything meaningful for PMU affinity.

If we need a mask, that should be something the FW description of the
PMU provides, and the PMU driver provides to the core code.

Thanks,
Mark.

  reply	other threads:[~2018-02-27 11:52 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-24  0:19 [PATCH v1 1/2] perf/core: Add API to look up PMU type by name Saravana Kannan
2018-02-24  0:19 ` Saravana Kannan
2018-02-24  0:19 ` [PATCH v1 2/2] perf/core: Add support for PMUs that can be read from any CPU Saravana Kannan
2018-02-24  0:19   ` Saravana Kannan
2018-02-24  0:56   ` Saravana Kannan
2018-02-24  0:56     ` Saravana Kannan
2018-02-24  8:41   ` Peter Zijlstra
2018-02-24  8:41     ` Peter Zijlstra
2018-02-27  1:53     ` skannan
2018-02-27  1:53       ` skannan at codeaurora.org
2018-02-27 11:52       ` Mark Rutland [this message]
2018-02-27 11:52         ` Mark Rutland
2018-03-03 15:41       ` Peter Zijlstra
2018-03-03 15:41         ` Peter Zijlstra
2018-03-07 16:39         ` Jeremy Linton
2018-03-07 16:39           ` Jeremy Linton
2018-02-25 14:38   ` Mark Rutland
2018-02-25 14:38     ` Mark Rutland
2018-02-27  2:11     ` skannan
2018-02-27  2:11       ` skannan at codeaurora.org
2018-02-27 11:43       ` Mark Rutland
2018-02-27 11:43         ` Mark Rutland
2018-02-27 23:15         ` skannan
2018-02-27 23:15           ` skannan at codeaurora.org
2018-02-24  8:08 ` [PATCH v1 1/2] perf/core: Add API to look up PMU type by name Peter Zijlstra
2018-02-24  8:08   ` Peter Zijlstra

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