From: Andrew Morton <akpm@linux-foundation.org>
To: Matthias Schniedermeyer <ms@citd.de>
Cc: linux-kernel@vger.kernel.org, David Chinner <dgc@sgi.com>,
Timothy Shimmin <tes@sgi.com>
Subject: Re: Why is deleting (or reading) files not counted as IO-Wait in top?
Date: Sat, 5 Jan 2008 01:31:15 -0800 [thread overview]
Message-ID: <20080105013115.217a5ab1.akpm@linux-foundation.org> (raw)
In-Reply-To: <20080102193503.GA31414@citd.de>
On Wed, 2 Jan 2008 20:35:03 +0100 Matthias Schniedermeyer <ms@citd.de> wrote:
> Hi
>
>
> Currently i'm deleting about 500.000 files on a XFS-filesystem which
> takes a few minutes, as i had a top open i saw that 'wa' is shown as
> 0.0% (Nothing else running currently) and everything except 'id' is near
> the bottom too. Kernel is 2.6.23.11.
>
> So, as 'rm -rf' is essentially a IO (or seek, to be more correct)-bound
> task, shouldn't that count as "Waiting for IO"?
>
> The man-page of top says:
> 'Amount of time the CPU has been waiting for I/O to complete.'
>
> But AFAICT wa only seams to be (ac)counted for writing and not for
> reading. I come to that conclusion because, when i fire 'sync' i can see
> some percent wa for a few seconds.
>
Yes, you would absolutely expect `rm' to be stuck in D state and
contributing to both load average and io-wait in this situation.
I'd think that either XFS is playing games (and it'd take some pretty
inventive games to do this) or your observations are in error.
next prev parent reply other threads:[~2008-01-05 9:31 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-02 19:35 Why is deleting (or reading) files not counted as IO-Wait in top? Matthias Schniedermeyer
2008-01-03 0:16 ` Maxim Levitsky
2008-01-03 8:25 ` Matthias Schniedermeyer
2008-01-05 9:31 ` Andrew Morton [this message]
2008-01-05 16:58 ` Matthias Schniedermeyer
2008-01-14 6:24 ` David Chinner
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