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>
Subject: Re: [PATCH v3] perf/core: Set event shadow time for inactive events too
Date: Thu, 9 Dec 2021 12:26:32 +0100 [thread overview]
Message-ID: <YbHn6JaaOo3b5GLO@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20211205224843.1503081-1-namhyung@kernel.org>
On Sun, Dec 05, 2021 at 02:48:43PM -0800, Namhyung Kim wrote:
> Actually 18446744069443110306 is 0xffffffff01b345a2 so it seems to
> have a negative enabled time. In fact, bperf keeps values returned by
> bpf_perf_event_read_value() which calls perf_event_read_local(), and
> accumulates delta between two calls. When event->shadow_ctx_time is
> not set, it'd return invalid enabled time which is bigger than normal.
*that*, how does it happen that shadow_time isn't set? It should be last
set when the event switches to INACTIVE, no? At which point the logic in
perf_event_read_local() should make @enabled move forward while @running
stays put.
Let me go rummage around a bit... either I'm missing something obvious
or something's smelly.
next prev parent reply other threads:[~2021-12-09 11:26 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 [this message]
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
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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