linux-kernel - Re: [RFC][PATCH] perf: Add a few generic stalled-cycles events

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Message-ID: <507C467E.8010205@fb.com>
Date:	Mon, 15 Oct 2012 10:23:10 -0700
From:	Arun Sharma <asharma@...com>
To:	Robert Richter <robert.richter@....com>
CC:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	<acme@...hat.com>, <mingo@...nel.org>, <peterz@...radead.org>,
	<eranian@...gle.com>, "Anton Blanchard" <anton@....ibm.com>,
	<paulus@...ba.org>, <mpjohn@...ibm.com>, <linuxppc-dev@...abs.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] perf: Add a few generic stalled-cycles events

On 10/15/12 8:55 AM, Robert Richter wrote:

[..]
> Perf tool works then out-of-the-box with:
>
>   $ perf record -e cpu/stalled-cycles-fixed-point/ ...
>
> The event string can easily be reused by other architectures as a
> quasi standard.

I like Robert's proposal better. It's hard to model all the stall events 
(eg: instruction decoder related stalls on x86) in a hardware 
independent way.

Another area to think about: software engineers are generally busy and 
have a limited amount of time to devote to hardware event based 
optimizations. The most common question I hear is: what is the expected 
perf gain if I fix this? It's hard to answer that with just the stall 
events.

  -Arun
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