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From: Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua>
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To: Andrew Morton <akpm@zip.com.au>, Rik van Riel <riel@conectiva.com.br>
Subject: Re: [RFC][PATCH] iowait statistics
Date: Wed, 15 May 2002 15:02:57 -0200
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On 14 May 2002 00:18, Andrew Morton wrote:
> Rik van Riel wrote:
> > 4) on SMP systems the iowait time can be overestimated, no big
> >    deal IMHO but cheap suggestions for improvement are welcome
>
> I suspect that a number of these statistical accounting mechanisms
> are going to break.  The new irq-affinity code works awfully well.
>
> The kernel profiler in 2.5 doesn't work very well at present.
> When investigating this, I ran a busy-wait process.  It attached
> itself to CPU #3 and that CPU received precisely zero interrupts
> across a five minute period.  So the profiler cunningly avoids profiling
> busy CPUs, which is rather counter-productive.  Fortunate that oprofile
> uses NMI.

What, even local APIC interrupts did not happen on CPU#3
in these five mins?
--
vda