Re: [PATCH] ignore referenced pages on reclaim when OOM

[Andrew Morton <akpm@osdl.org>]

Rik van Riel <riel@redhat.com> wrote:
>
> On Tue, 9 Nov 2004, Nikita Danilov wrote:
> 
> >  > Speeds up extreme load performance on Rik's tests.
> > 
> > I recently tested quite similar thing, the only dfference being that in
> > my case references bit started being ignored when scanning priority
> > reached 2 rather than 0.
> > 
> > I found that it _degrades_ performance in the loads when there is a lot
> > of file system write-back going from tail of the inactive list (like
> > dirtying huge file through mmap in a loop).
> 
> Well yeah, when you reach priority 2, you've only scanned
> 1/4 of memory.  On the other hand, when you reach priority
> 0, you've already scanned all pages once - beyond that point
> the referenced bit really doesn't buy you much any more.
> 

But we have to scan active, referenced pages two times to move them onto
the inactive list.  A bit more, really, because nowadays
refill_inactive_zone() doesn't even run page_referenced() until it starts
to reach higher scanning priorities.

So it could be that we're just not scanning enough.
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