linux-kernel - Re: [PATCH] sched: Provide iowait counters

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Message-ID: <4A6B4E28.7000207@linux.intel.com>
Date:	Sat, 25 Jul 2009 11:25:44 -0700
From:	Arjan van de Ven <arjan@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	"Kok, Auke-jan H" <auke-jan.h.kok@...el.com>
Subject: Re: [PATCH] sched: Provide iowait counters

Peter Zijlstra wrote:
> On Sat, 2009-07-25 at 09:42 -0700, Arjan van de Ven wrote:
>> In case you wonder why you need both tools, and can't just use one: we
>> wondered the same, but it turns out that if you only build
>> Tool Two, you don't get a good overview of what is going on on a
>> higher level. It's like looking at the world via a microscope all the
>> time,
> 
> I'd be thinking you could compose your ms based picture on the sample
> data. For instance, if you sample on cpu-clock at 100kHz, then a 100
> samples get you a full blue slice, 50 get you a 50% blue slice, etc.
> 
> Of course, since its sample based, you can miss some detail, but I think
> you're looking at the large picture anyway.
> 
> Would this work?
> 

ok thinking some more, in principle we can make a hybrid, that only uses the
perf data, as long as the perf data includes run/iowait/woken events.
(and process exit, name change. ideally also exec).
We'll just poll /proc only for the io throughput data, and collect that on a 1 msec
scale.
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