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    SubjectRe: [PATCH 3/3][RFC] swsusp: shrink file cache first
    On Fri, Feb 06, 2009 at 01:00:09PM -0800, Andrew Morton wrote:
    > On Fri, 6 Feb 2009 05:49:07 +0100
    > Johannes Weiner <> wrote:
    > > > and, I think you should mesure performence result.
    > >
    > > Yes, I'm still thinking about ideas how to quantify it properly. I
    > > have not yet found a reliable way to check for whether the working set
    > > is intact besides seeing whether the resumed applications are
    > > responsive right away or if they first have to swap in their pages
    > > again.
    > Describing your subjective non-quantitative impressions would be better
    > than nothing...


    > The patch bugs me.

    Please ignore it, it is broken as is. My verbal cortex got obviously
    disconnected from my code cortex when writing the changelog... And I
    will reconsider the actual change bits, I still think that we
    shouldn't scan anon page lists while may_swap is zero.

    > The whole darn point behind the whole darn page reclaim is "reclaim the
    > pages which we aren't likely to need soon". There's nothing special
    > about the swsusp code at all! We want it to do exactly what page
    > reclaim normally does, only faster.
    > So why do we need to write special hand-rolled code to implement
    > something which we've already spent ten years writing?
    > hm? And if this approach leads to less-than-optimum performance after
    > resume then the fault lies with core page reclaim - it reclaimed the
    > wrong pages!
    > That actually was my thinking when I first worked on
    > shrink_all_memory() and it did turn out to be surprisingly hard to
    > simply reuse the existing reclaim code for this application. Things
    > kept on going wrong. IIRC this was because we were freeing pages as we
    > were reclaiming, so the page reclaim logic kept on seeing all these
    > free pages and kept on wanting to bale out.
    > Now, the simple and obvious fix to this is not to free the pages - just
    > keep on allocating pages and storing them locally until we have
    > "enough" memory. Then when we're all done, dump them all straight onto
    > to the freelists.
    > But for some reason which I do not recall, we couldn't do that.
    > It would be good to revisit all this.

    Thanks for the comments, I will see what I can come up with.


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