Re: [PATCH] mm: Implement Swap Prefetching v25

[Christoph Lameter]

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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