From: Peter Zijlstra <peterz@infradead.org>
To: Song Liu <songliubraving@fb.com>
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: Mon, 20 Dec 2021 10:54:55 +0100 [thread overview]
Message-ID: <YcBS75PpjOujBTUe@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <YcBNOsMG3aGVpnWK@hirez.programming.kicks-ass.net>
On Mon, Dec 20, 2021 at 10:30:34AM +0100, Peter Zijlstra wrote:
> On Sat, Dec 18, 2021 at 09:09:05AM +0000, Song Liu wrote:
> > 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?
>
> Ohh.. argh. I think I see why, it looses the context time enable edge,
> and because this is all strictly per-event in the uapi (there is no ctx
> representation) it can't be cured by improving ctx time handling :/
>
> Bah, I so hate this.
For now I've added this then ...
+/*
+ * Because the userpage is strictly per-event (there is no concept of context,
+ * so there cannot be a context indirection), every userpage must be updated
+ * when context time starts :-(
+ *
+ * IOW, we must not miss EVENT_TIME edges.
+ */
static inline bool event_update_userpage(struct perf_event *event)
But that same is not true for perf_event_read_local(), that *has* access
to the context and so must be able to DTRT.
next prev parent reply other threads:[~2021-12-20 9:55 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
2021-12-20 9:30 ` Peter Zijlstra
2021-12-20 9:54 ` Peter Zijlstra [this message]
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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