From: Peter Zijlstra <peterz@infradead.org>
To: Namhyung Kim <namhyung@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Jiri Olsa <jolsa@redhat.com>, Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
LKML <linux-kernel@vger.kernel.org>,
Stephane Eranian <eranian@google.com>,
Andi Kleen <ak@linux.intel.com>, Ian Rogers <irogers@google.com>,
Song Liu <songliubraving@fb.com>, Tejun Heo <tj@kernel.org>,
kernel test robot <lkp@intel.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v3 1/2] perf/core: Share an event with multiple cgroups
Date: Tue, 20 Apr 2021 20:43:36 +0200 [thread overview]
Message-ID: <YH8g2EPn+2cvN3JA@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAM9d7chaxr4o3iY1Y+Z9W0C5rZ7gazvUA2U+Uq_L6CHaHsFqGA@mail.gmail.com>
On Wed, Apr 21, 2021 at 03:37:11AM +0900, Namhyung Kim wrote:
> On Tue, Apr 20, 2021 at 7:28 PM Peter Zijlstra <peterz@infradead.org> wrote:
> > You forgot NMI.
>
> Thanks for your explanation. Maybe I'm missing something but
> this event is basically for counting and doesn't allow sampling.
> Do you say it's affected by other sampling events? Note that
> it's not reading from the PMU here, what it reads is a snapshot
> of last pmu->read(event) afaik.
Even !sampling events will trigger NMI to deal with short hardware
counters rolling over. But yes, !sampling can also be updated from NMI
by other events if they're in a group etc..
Basically, always assume NMI/PMI can happen.
next prev parent reply other threads:[~2021-04-20 18:45 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 15:53 [PATCH v3 0/2] perf core: Sharing events with multiple cgroups Namhyung Kim
2021-04-13 15:53 ` [PATCH v3 1/2] perf/core: Share an event " Namhyung Kim
2021-04-15 14:51 ` Peter Zijlstra
2021-04-15 23:48 ` Namhyung Kim
2021-04-16 9:26 ` Peter Zijlstra
2021-04-16 9:29 ` Peter Zijlstra
2021-04-16 10:19 ` Namhyung Kim
2021-04-16 10:27 ` Peter Zijlstra
2021-04-16 11:22 ` Namhyung Kim
2021-04-16 11:59 ` Peter Zijlstra
2021-04-16 12:19 ` Namhyung Kim
2021-04-16 13:39 ` Peter Zijlstra
2021-05-09 7:13 ` Namhyung Kim
2021-04-16 10:18 ` Namhyung Kim
2021-04-16 9:49 ` Namhyung Kim
2021-04-20 10:28 ` Peter Zijlstra
2021-04-20 18:37 ` Namhyung Kim
2021-04-20 18:43 ` Peter Zijlstra [this message]
2021-04-20 8:34 ` Stephane Eranian
2021-04-20 9:48 ` Peter Zijlstra
2021-04-20 11:28 ` Peter Zijlstra
2021-04-21 19:37 ` Namhyung Kim
2021-05-03 21:53 ` Namhyung Kim
2021-04-13 15:53 ` [PATCH v3 2/2] perf/core: Support reading group events with shared cgroups Namhyung Kim
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