linux-kernel - Re: [PATCH] mm: swap prefetch more improvements

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Date:	Tue, 15 May 2007 11:58:01 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Con Kolivas <kernel@...ivas.org>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, ck@....kolivas.org
Subject: Re: [PATCH] mm: swap prefetch more improvements

On Mon, 2007-05-14 at 15:00 -0700, Andrew Morton wrote:
> On Mon, 14 May 2007 10:50:54 +1000
> Con Kolivas <kernel@...ivas.org> wrote:
> 
> > akpm, please queue on top of "mm: swap prefetch improvements"
> > 
> > ---
> > Failed radix_tree_insert wasn't being handled leaving stale kmem.
> > 
> > The list should be iterated over in the reverse order when prefetching.
> > 
> > Make the yield within kprefetchd stronger through the use of cond_resched.
> 
> hm.
> 
> > 
> > -		might_sleep();
> > -		if (!prefetch_suitable())
> > +		/* Yield to anything else running */
> > +		if (cond_resched() || !prefetch_suitable())
> >  			goto out_unlocked;
> 
> So if cond_resched() happened to schedule away, we terminate this
> swap-tricking attempt.  It's not possible to determine the reasons for this
> from the code or from the changelog (==bad).
> 
> How come?

I think Con meant need_resched(). That would indicate someone else wants
to use the CPU and and has higher priority than kprefetchd.



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