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    SubjectRe: swsusp performance problems in 2.6.15-rc3-mm1
    Hi!

    > Newer kernels write and read a bigger image, which makes the prompt show
    > up somewhat later, but gives the benefit of putting me back in
    > approximately the same place I left off with regards to working set.
    >
    > I would like the best of both worlds - I want my suspend to go faster
    > (so I want a smaller image), and I also want my working set paged back
    > in after resume.
    >
    > I'm assuming that the difference is that with Rafael's patches, clean
    > pages that would have been evicted in the "freeing pages..." step are
    > now being written out to the swsusp image. If so, this is a waste - no
    > point in having the data on disk twice. (It would be nice to confirm
    > this suspicion.)

    Confirmed. But you are wrong; it is not a waste. The pages are nicely
    linear in suspend image, while they would be all over the disk
    otherwise. There can easily be factor 20 difference between linear
    read and random read.

    > Could we rework it to avoid writing clean pages out to the swsusp image,
    > but keep a list of those pages and read them back in *after* having
    > resumed? Maybe do the /dev/initrd ('less +/once Documentation/initrd.txt'
    > if you're not familiar with it) trick to make the list of pages available
    > to a userland helper.

    I did not understand this one.

    > Someone suggested the 'cat `grep / /proc/*/maps`' trick. This kills the
    > working set calculations that the kernel has so painstakingly built up,
    > reading in all kinds of pages that were flushed with good reason, and
    > also fails to get my Mercurial .d files back into cache, since they are
    > not mapped by any long-running process.

    Yes, that was very rough approximation.

    Anyway, try limiting size of image to ~500MB, first. Should solve your
    problem with very little work.
    Pavel
    --
    Thanks, Sharp!
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