linux-kernel - Re: [RFC][PATCH 11/11] perf: Rework the PMU methods

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Message-ID: <20100629153753.GI5318@nowhere>
Date:	Tue, 29 Jun 2010 17:37:56 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	paulus <paulus@...ba.org>,
	stephane eranian <eranian@...glemail.com>,
	Robert Richter <robert.richter@....com>,
	Will Deacon <will.deacon@....com>,
	Paul Mundt <lethal@...ux-sh.org>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Lin Ming <ming.m.lin@...el.com>,
	Yanmin <yanmin_zhang@...ux.intel.com>,
	Deng-Cheng Zhu <dengcheng.zhu@...il.com>,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 11/11] perf: Rework the PMU methods

On Thu, Jun 24, 2010 at 04:28:15PM +0200, Peter Zijlstra wrote:
> Replace pmu::{enable,disable,start,stop,unthrottle} with
> pmu::{add,del,start,stop}, all of which take a flags argument.
> 
> The new interface extends the capability to stop a counter while
> keeping it scheduled on the PMU. We replace the throttled state with
> the generic stopped state.
> 
> This also allows us to efficiently stop/start counters over certain
> code paths (like IRQ handlers).
> 
> It also allows scheduling a counter without it starting, allowing for
> a generic frozen state (useful for rotating stopped counters).
> 
> The stopped state is implemented in two different ways, depending on
> how the architecture implemented the throttled state:
> 
>  1) We disable the counter:
>     a) the pmu has per-counter enable bits, we flip that
>     b) we program a NOP event, preserving the counter state
> 
>  2) We store the counter state and ignore all read/overflow events
> 
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>


Acked-by: Frederic Weisbecker <fweisbec@...il.com>

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