From: Song Liu <songliubraving@fb.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Namhyung Kim <namhyung@kernel.org>,
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>
Subject: Re: [PATCH v3] perf/core: Set event shadow time for inactive events too
Date: Sat, 18 Dec 2021 09:09:05 +0000 [thread overview]
Message-ID: <7A415BC0-E6F2-4ED2-8996-8F5871ED8001@fb.com> (raw)
In-Reply-To: <Yby8Su+fVA1lqVjT@hirez.programming.kicks-ass.net>
> On Dec 17, 2021, at 8:35 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Fri, Dec 10, 2021 at 11:33:41AM +0100, Peter Zijlstra wrote:
>
>> I'm thinking this is a cgroup specific thing. Normally the shadow_time
>> thing is simply a relative displacement between event-time and the
>> global clock. That displacement never changes, except when you do
>> IOC_DISABLE/IOC_ENABLE.
>>
>> However, for cgroup things are different, since the cgroup events aren't
>> unconditionally runnable, that is, the enabled time should only count
>> when the cgroup is active, right?
>>
>> So perhaps perf_event_read_local() should use a cgroup clock instead of
>> perf_clock() for cgroup events.
>>
>> Let me think about that some more...
>
> How's this then? Song, could you also please test and or better explain
> the problem f79256532682 pretends to cure? Because the below is
> reverting that, I *really* hate having to touch the events we're not
> scheduling.
Unfortunately, this change bring the bug back. For time_enabled in rdpmc
case to work properly, we have to touch all the enabled but not running
events, right?
Thanks,
Song
[...]
next prev parent reply other threads:[~2021-12-18 9:09 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-05 22:48 [PATCH v3] perf/core: Set event shadow time for inactive events too Namhyung Kim
2021-12-06 23:11 ` Song Liu
2021-12-08 23:22 ` Peter Zijlstra
2021-12-09 5:52 ` Namhyung Kim
2021-12-09 8:21 ` Peter Zijlstra
2021-12-09 11:26 ` Peter Zijlstra
2021-12-09 11:34 ` Peter Zijlstra
2021-12-09 21:51 ` Namhyung Kim
2021-12-10 10:19 ` Peter Zijlstra
2021-12-10 18:59 ` Namhyung Kim
2021-12-20 9:39 ` Peter Zijlstra
2021-12-09 21:35 ` Namhyung Kim
2021-12-10 10:33 ` Peter Zijlstra
2021-12-10 23:19 ` Namhyung Kim
2021-12-17 16:35 ` Peter Zijlstra
2021-12-18 9:09 ` Song Liu [this message]
2021-12-20 9:30 ` Peter Zijlstra
2021-12-20 9:54 ` Peter Zijlstra
2021-12-21 12:39 ` Peter Zijlstra
2021-12-20 12:19 ` Peter Zijlstra
2021-12-21 5:54 ` Namhyung Kim
2021-12-21 7:23 ` Song Liu
2021-12-21 11:21 ` Peter Zijlstra
2022-01-18 11:17 ` [tip: perf/urgent] perf: Fix perf_event_read_local() time tip-bot2 for Peter Zijlstra
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