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Message-ID: <20070522203116.GA8656@elte.hu>
Date: Tue, 22 May 2007 22:31:16 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Michael Chang <thenewme91@...il.com>
Cc: Con Kolivas <kernel@...ivas.org>,
Nick Piggin <nickpiggin@...oo.com.au>,
Ray Lee <ray-lk@...rabbit.org>, linux-kernel@...r.kernel.org,
ck list <ck@....kolivas.org>, linux-mm@...ck.org,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [ck] Re: [PATCH] mm: swap prefetch improvements
* Michael Chang <thenewme91@...il.com> wrote:
> > It clearly should not consider 'itself' as IO activity. This
> > suggests some bug in the 'detect activity' mechanism, agreed? I'm
> > wondering whether you are seeing the same problem, or is all
> > swap-prefetch IO on your system continuous until it's done [or some
> > other IO comes inbetween]?
>
> The only "problem" I can see with this idea is in the potential case
> that it takes up all the IO activity, and so there is never enough IO
> activity from other progams to trigger the wait mechanism because they
> don't get a chance to run.
i dont understand what you mean. Any 'use only idle IO capacity'
mechanism should immediately cease to be active the moment any other app
tries to do IO - whether the IO subsystem is saturated or not.
> That said, I don't think there are any issues with the code
> compensating for its own activity in the "detect activity" mechanism
> -- assuming there wasn't a major impact in e.g. maintainability or
> something.
>
> As for the burstyness... considering the "no negative impact" stance,
> I can understand that. But it seems inefficient, at best...
well, it's a plain old bug (a not too serious one) in my book, i'm
surprised that we are now at mail #7 about it :-) I reported it, and i
guess Con will fix it eventually. There's really no need to deny that it
exists or to try to talk it out of existence. Sheesh! :-)
Ingo
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