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

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Message-Id: <200705152243.57871.kernel@kolivas.org>
Date:	Tue, 15 May 2007 22:43:57 +1000
From:	Con Kolivas <kernel@...ivas.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	ck@....kolivas.org
Subject: Re: [PATCH] mm: swap prefetch more improvements

On Tuesday 15 May 2007 19:58, Peter Zijlstra wrote:
> 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.

It may well be that need_resched is what I was trying to do... I don't need it 
to do the resched and _then_ break out of swap prefetch.

-- 
-ck
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