Re: [ck] swap prefetching merge plans

[Nick Piggin]

jos poortvliet wrote:
> Op donderdag 23 maart 2006 08:04, schreef Con Kolivas:
>
> > On Thu, 23 Mar 2006 03:53 pm, Andrew Morton wrote:
> >
> > > A look at the -mm lineup for 2.6.17:
> > >
> > > mm-implement-swap-prefetching.patch
> > > mm-implement-swap-prefetching-fix.patch
> > > mm-implement-swap-prefetching-tweaks.patch
> > >
> > >  Still don't have a compelling argument for this, IMO.
>
>
> well, the reason i use it is my computer is much more reactive in the morning. 
> linux uses to get very slow after a night of not-doing-much except some 
> 'sleep 5h && blabla' and cron stuff. in the morning it takes a few HOURS to 
> get up and running smoothly. with swap prefetch, it actually feels faster 
> compared to a fresh boot. now you can force swap prefetch to start working, i 
> use it now and then after some heavy taskts which pulled everything to swap.

I have two issues with this argument (not that I'm trying to say it
couldn't make a difference in your case).

Firstly, swap prefetch actually doesn't handle the midnight updatedb pageout
problem nicely. It doesn't do any prefetching when the pagecache/vfs cache
fills memory (which is what would have to happen for updatedb to push stuff
into swap).

Secondly, with or without swap prefetch, I think we can do a better job of
handling these use-once patterns to begin with.

--
SUSE Labs, Novell Inc.
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