Date: Tue, 7 Mar 2006 16:05:15 -0800
From: Andrew Morton <akpm@osdl.org>
To: Con Kolivas <kernel@kolivas.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, ck@vds.kolivas.org
Subject: Re: [PATCH] mm: yield during swap prefetching
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Con Kolivas <kernel@kolivas.org> wrote:
>
> > yield() really sucks if there are a lot of runnable tasks.  And the amount
> > of CPU which that thread uses isn't likely to matter anyway.
> > 
> > I think it'd be better to just not do this.  Perhaps alter the thread's
> > static priority instead?  Does the scheduler have a knob which can be used
> > to disable a tasks's dynamic priority boost heuristic?
> 
> We do have SCHED_BATCH but even that doesn't really have the desired effect. 
> I know how much yield sucks and I actually want it to suck as much as yield 
> does.

Why do you want that?

If prefetch is doing its job then it will save the machine from a pile of
major faults in the near future.  The fact that the machine happens to be
running a number of busy tasks doesn't alter that.  It's _worth_ stealing a
few cycles from those tasks now to avoid lengthy D-state sleeps in the near
future?
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