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From: Peter Zijlstra <peterz@infradead.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-kernel@vger.kernel.org, will.deacon@arm.com,
	dave.martin@arm.com, Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH 7/7] perf: kill perf_event_context::pmu
Date: Mon, 10 Feb 2014 19:10:26 +0100	[thread overview]
Message-ID: <20140210181026.GD27965@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1392054264-23570-8-git-send-email-mark.rutland@arm.com>

On Mon, Feb 10, 2014 at 05:44:24PM +0000, Mark Rutland wrote:
> Currently portions of the perf subsystem assume that a
> perf_event_context is associated with a single pmu while in reality a
> single perf_event_context may be shared by a number of pmus, as commit
> 443772776c69 (perf: Disable all pmus on unthrottling and rescheduling)
> describes.
> 
> This patch removes perf_event_context::pmu, replacing it with a direct
> pointer to the associated perf_cpu_context and a task_ctx_nr (as all
> pmus sharing a context have the same task_ctx_nr). This makes the
> relationship between pmus and perf_event_contexts clearer and allows us
> to save on some pointer chasing.
> 
> This also fixes a potential misuse of ctx->pmu introduced in commit
> bad7192b842c (perf: Fix PERF_EVENT_IOC_PERIOD to force-reset the
> period), where ctx->pmu is disabled before modifying state on
> event->pmu. In this case the two pmus are not guaranteed to be the same.
> 
> As perf_pmu_rotate_{start,stop} only really care about the context they
> are rotating, they are renamed to perf_event_ctx_{start,stop}.

This very much relies on the previous patch where you make pmu_disable
iterate all the events.

We could also change this to keep a pmu list for each context and
iterate that instead. Given there is indeed a fair limit on different
PMUs in the system that iteration should be much shorter.



  reply	other threads:[~2014-02-10 18:10 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-10 17:44 [PATCH 0/7] Perf core cleanups for shared perf_event_contexts Mark Rutland
2014-02-10 17:44 ` [PATCH 1/7] perf: fix prototype of find_pmu_context Mark Rutland
2014-02-27 13:33   ` [tip:perf/core] perf: Fix prototype of find_pmu_context() tip-bot for Mark Rutland
2014-02-10 17:44 ` [PATCH 2/7] perf: remove redundant pmu assignment Mark Rutland
2014-02-27 13:33   ` [tip:perf/core] perf: Remove redundant PMU assignment tip-bot for Mark Rutland
2014-02-10 17:44 ` [PATCH 3/7] perf: kill perf_event_context_type Mark Rutland
2014-02-25 11:38   ` Peter Zijlstra
2014-02-27 11:46     ` Mark Rutland
2014-02-10 17:44 ` [PATCH 4/7] perf: be less pessimistic when scheduling events Mark Rutland
2014-02-10 17:58   ` Peter Zijlstra
2014-02-11 17:48     ` Mark Rutland
2014-02-25 11:29       ` Peter Zijlstra
2014-02-27 12:07         ` Mark Rutland
2014-02-10 17:44 ` [PATCH 5/7] perf: kill pmu::hrtimer_interval_ms Mark Rutland
2014-02-10 17:44 ` [PATCH 6/7] perf: Centralise context pmu disabling Mark Rutland
2014-02-10 18:08   ` Peter Zijlstra
2014-02-10 17:44 ` [PATCH 7/7] perf: kill perf_event_context::pmu Mark Rutland
2014-02-10 18:10   ` Peter Zijlstra [this message]
2014-02-11 17:56     ` Mark Rutland
2014-02-12 15:01       ` Dave Martin
2014-02-25 11:31       ` Peter Zijlstra
2014-02-27 11:48         ` Mark Rutland
2014-02-27 11:51           ` Peter Zijlstra
2014-02-27 12:30             ` Mark Rutland
2014-02-19 13:43 ` [PATCH 0/7] Perf core cleanups for shared perf_event_contexts Mark Rutland
2014-02-25 11:39   ` Peter Zijlstra

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