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    SubjectRe: fadvise DONTNEED implementation (or lack thereof)
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    > On Tue,  9 Nov 2010 16:28:02 +0900 (JST), KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> wrote:
    > > So, I don't think application developers will use fadvise() aggressively
    > > because we don't have a cross platform agreement of a fadvice behavior.
    > >
    > I strongly disagree. For a long time I have been trying to resolve
    > interactivity issues caused by my rsync-based backup script. Many kernel
    > developers have said that there is nothing the kernel can do without
    > more information from user-space (e.g. cgroups, madvise). While cgroups
    > help, the fix is round-about at best and requires configuration where
    > really none should be necessary. The easiest solution for everyone
    > involved would be for rsync to use FADV_DONTNEED. The behavior doesn't
    > need to be perfectly consistent between platforms for the flag to be
    > useful so long as each implementation does something sane to help
    > use-once access patterns.
    >
    > People seem to mention frequently that there are no users of
    > FADV_DONTNEED and therefore we don't need to implement it. It seems like
    > this is ignoring an obvious catch-22. Currently rsync has no fadvise
    > support at all, since using[1] the implemented hints to get the desired
    > effect is far too complicated^M^M^M^Mhacky to be considered
    > merge-worthy. Considering the number of Google hits returned for
    > fadvise, I wouldn't be surprised if there were countless other projects
    > with this same difficulty. We want to be able to tell the kernel about
    > our useage patterns, but the kernel won't listen.

    Because we have an alternative solution already. please try memcgroup :)





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