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Date: Tue, 8 Jan 2002 19:24:04 -0200 (BRST)
From: Rik van Riel <riel@conectiva.com.br>
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To: Robert Love <rml@tech9.net>
Cc: Daniel Phillips <phillips@bonn-fries.net>, Andrew Morton <akpm@zip.com.au>,
        Anton Blanchard <anton@samba.org>, Andrea Arcangeli <andrea@suse.de>,
        Luigi Genoni <kernel@Expansa.sns.it>,
        Dieter N?tzel <Dieter.Nuetzel@hamburg.de>,
        Marcelo Tosatti <marcelo@conectiva.com.br>,
        Linux Kernel List <linux-kernel@vger.kernel.org>
Subject: Re: [2.4.17/18pre] VM and swap - it's really unusable
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On 8 Jan 2002, Robert Love wrote:
> On Tue, 2002-01-08 at 16:08, Rik van Riel wrote:
>
> > The preemptible kernel ALSO has to wait for a scheduling point
> > to roll around, since it cannot preempt with spinlocks held.
> >
> > Considering this, I don't see much of an advantage to adding
> > kernel preemption.
>
> It only has to wait if locks are held and then only until the locks are
> dropped.  Otherwise it will preempt on the next return from interrupt.

So what exactly _is_ the difference between an explicit
preemption point and a place where we need to explicitly
drop a spinlock ?

>From what I can see, there really isn't a difference.

> Future work would be to look into long-held locks and see what we can
> do.

One thing we could do is download Andrew Morton's patch ;)

Rik
-- 
"Linux holds advantages over the single-vendor commercial OS"
    -- Microsoft's "Competing with Linux" document

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