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SubjectRe: [PATCH -mm 00/25] VM pageout scalability improvements (V10)
On Fri, 6 Jun 2008 14:02:16 -0700
Andrew Morton <> wrote:
> On Fri, 06 Jun 2008 16:28:38 -0400
> Rik van Riel <> wrote:
> > On large memory systems, the VM can spend way too much time scanning
> > through pages that it cannot (or should not) evict from memory. Not
> > only does it use up CPU time, but it also provokes lock contention
> > and can leave large systems under memory presure in a catatonic state.
> >
> > Against 2.6.26-rc2-mm1
> >
> > This patch series improves VM scalability by:
> -mm has a patch called
> vmscan-give-referenced-active-and-unmapped-pages-a-second-trip-around-the-lru.patch
> which has been sitting there for some time waiting for us to work out
> whether or not it is a desirable thing.
> This patchset of yours apparently retains the change which
> vmscan-give-referenced-active-and-unmapped-pages-a-second-trip-around-the-lru.patch
> makes.
> But do we know that it was a good one?

Benchmark results here indicate that it helps some workloads by up
to 10%, but makes the page cache pages that fall off of the active
list more prone to being replaced by streaming IO.

I have added in a fix in this series to set the referenced bit on
unmapped page cache pages that get deactivated, so that defect is

I've been busy with some other stuff this week; I'll try to get
you some numbers ASAP.

All rights reversed.

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