From: Peter Zijlstra <peterz@infradead.org>
To: skannan@codeaurora.org
Cc: mark.rutland@arm.com, 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: Sat, 3 Mar 2018 16:41:13 +0100 [thread overview]
Message-ID: <20180303154113.GH25201@hirez.programming.kicks-ass.net> (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". When I
> say clusters, I using the more common interpretation of "homogeneous CPUs
> running on the same clock"/CPUs in a cpufreq policy and not ARM's new
> redefinition of cluster. So, on a SoC with 4 little and 4 big cores, it'll
> still trigger a lot of unnecessary smp calls/IPIs that cause unnecessary
> wakeups.
arch/arm64/include/asm/topology.h:#define topology_physical_package_id(cpu) (cpu_topology[cpu].cluster_id)
*sigh*... that's just broken...
next prev parent reply other threads:[~2018-03-03 15:41 UTC|newest]
Thread overview: 13+ 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 ` [PATCH v1 2/2] perf/core: Add support for PMUs that can be read from any CPU Saravana Kannan
2018-02-24 0:56 ` Saravana Kannan
2018-02-24 8:41 ` Peter Zijlstra
2018-02-27 1:53 ` skannan
2018-02-27 11:52 ` Mark Rutland
2018-03-03 15:41 ` Peter Zijlstra [this message]
2018-03-07 16:39 ` Jeremy Linton
2018-02-25 14:38 ` Mark Rutland
2018-02-27 2:11 ` skannan
2018-02-27 11:43 ` Mark Rutland
2018-02-27 23:15 ` skannan
2018-02-24 8:08 ` [PATCH v1 1/2] perf/core: Add API to look up PMU type by name Peter Zijlstra
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