Date: Mon, 13 Feb 2006 12:58:58 -0800 (PST)
From: Christoph Lameter <clameter@engr.sgi.com>
To: Con Kolivas <kernel@kolivas.org>
cc: linux kernel mailing list <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>, ck list <ck@vds.kolivas.org>
Subject: Re: [PATCH] mm: Implement Swap Prefetching v25
In-Reply-To: <200602120141.46084.kernel@kolivas.org>
Message-ID: <Pine.LNX.4.62.0602131256000.3026@schroedinger.engr.sgi.com>
References: <200602120141.46084.kernel@kolivas.org>
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On Sun, 12 Feb 2006, Con Kolivas wrote:

> Once pages have been added to the swapped list, a timer is started, testing
> for conditions suitable to prefetch swap pages every 5 seconds. Suitable
> conditions are defined as lack of swapping out or in any pages, and no
> watermark tests failing. Significant amounts of dirtied ram and changes in
> free ram representing disk writes or reads also prevent prefetching.
> 
> It then checks that we have spare ram looking for at least 3* pages_high free
> per zone and if it succeeds that will prefetch pages from swap into the swap
> cache. The pages are added to the tail of the inactive list to preserve LRU
> ordering.

spare ram when swapping??? We are already under memory pressure. Why make 
it worse by getting rid of the few bits of available memory? If a system 
swaps then we are per definition in the bad performance range. Add more
memory.
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