Re: [PATCH] swapin readahead and fixes

[Drago Goricanec <drago@king.otsd.ts.fujitsu.co.jp>]

On Tue, 8 Dec 1998 03:31:25 +0100 (CET), Rik van Riel writes:

> On a swapout, we will scan ahead of where we are (p->swap_address)
> and swap out the next number of pages too. We break the loop if:
> - the page isn't present or already in swap
> - the next two pages were touched since our last scan
> - the page isn't allocated
> - we reach the end of a SWAP_CLUSTER area in swap space
> 
> If we write this way (no more expensive than normal because
> we write the stuff in one disk movement) swapin readahead
> will be much more effective and performance will increase.

Except for disk I/O bound processes, where the swapout writeahead
steals some extra time from the disk.  I guess this is where having
separate swap and data disks would help.

Looking forward to trying out your patches myself.

Drago


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