Date: Thu, 9 Sep 2004 14:28:01 -0700
From: Andrew Morton <akpm@osdl.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: mingo@elte.hu, rlrevell@joe-job.com, linux-kernel@vger.kernel.org,
       felipe_alfaro@linuxmail.org, mista.tapas@gmx.net, kr@cybsft.com,
       Mark_H_Johnson@Raytheon.com
Subject: Re: [patch] voluntary-preempt-2.6.9-rc1-bk12-R6
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Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
>
> I would still expect the only thing to materially improve swap latency
> to be a log structured swap, possibly with a cleaner which tidies
> together pages that are referenced together.
> 

Maybe.  It'd be nice to show some benefit from the "organise pages by
virtual address" patch first.

But then, maybe that doesn't help because there is little correlation
between address congruency and time-of-reference.  That's hard to believe
though.

hm.  The patch _does_ do what I wanted it to do.  Maybe I tested it with
silly workloads.

> 
> You also want contiguous runs of at least 64K and probaly a lot more on
> bigger memory systems. 

I used 1MB.

+/*
+ * We divide the swapdev into 1024 kilobyte chunks.  We use the cookie and the
+ * upper bits of the index to select a chunk and the rest of the index as the
+ * offset into the selected chunk.
+ */
+#define CHUNK_SHIFT	(20 - PAGE_SHIFT)

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