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From: Denis Vlasenko <vda@port.imtp.ilyichevsk.odessa.ua>
To: Rik van Riel <riel@conectiva.com.br>
Cc: <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>
Subject: Re: [RFC][PATCH] iowait statistics
Date: Wed, 15 May 2002 18:17:22 -0200	[thread overview]
Message-ID: <200205151514.g4FFEmY13920@Port.imtp.ilyichevsk.odessa.ua> (raw)
In-Reply-To: <Pine.LNX.4.44L.0205151102030.9490-100000@duckman.distro.conectiva>

On 15 May 2002 12:03, Rik van Riel wrote:
> > I was investigating why sometimes in top I see idle % like
> > 9384729374923.43%. It was caused by idle count in /proc/stat
> > going backward sometimes.
>
> Thanks for tracking down this bug.
>
> > It can be fixed for SMP:
> > * add spinlock
> > or
> > * add per_cpu_idle, account it too at timer/APIC int
> >   and get rid of idle % calculations for /proc/stat
> >
> > As a user, I vote for glitchless statistics even if they
> > consume extra i++ cycle every timer int on every CPU.
>
> Same for me. The last option is probably easiest to implement
> and cheapest at run time.

I think two patches for same kernel piece at the same time is
too many. Go ahead and code this if you want.

> The extra "cost" will approach zero
> once somebody takes the time to put the per-cpu stats on per
> cpu cache lines, which I'm sure somebody will do once we have
> enough per-cpu stats ;)

I thought about that too: per_cpu_xxx[cpu] -> per_cpu[cpu].xxx
type thing.
--
vda

  reply	other threads:[~2002-05-15 15:19 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-05-14  1:19 [RFC][PATCH] iowait statistics Rik van Riel
2002-05-14  2:18 ` Andrew Morton
2002-05-14 12:30   ` Rik van Riel
2002-05-15 17:02   ` Denis Vlasenko
2002-05-16  7:41     ` Andrew Morton
2002-05-16 14:04       ` Denis Vlasenko
2002-05-14 15:39 ` William Lee Irwin III
2002-05-14 16:36   ` Rik van Riel
2002-05-14 16:54     ` William Lee Irwin III
2002-05-15 17:17       ` Denis Vlasenko
2002-05-15 14:03         ` Rik van Riel
2002-05-15 20:17           ` Denis Vlasenko [this message]
2002-05-15 16:13             ` Rik van Riel
2002-05-15 16:21               ` William Lee Irwin III
2002-05-15 17:00               ` William Lee Irwin III
2002-05-15 18:16                 ` Bill Davidsen
2002-05-15 18:30                 ` William Lee Irwin III
2002-05-15 18:33                   ` Rik van Riel
2002-05-15 18:46                     ` William Lee Irwin III
2002-05-15 19:00                       ` Rik van Riel
2002-05-16 11:42                         ` Denis Vlasenko
2002-05-16 11:14               ` Denis Vlasenko
2002-05-15 15:15         ` Bill Davidsen
2002-05-16 10:58           ` Denis Vlasenko
2002-05-14 18:19     ` Martin J. Bligh
2002-05-15  1:31 ` Bill Davidsen
2002-05-15  1:41   ` William Lee Irwin III
2002-05-15 14:39     ` Bill Davidsen

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