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    SubjectRe: [RFC 1/2] deactive invalidated pages
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    On Tue, Nov 23, 2010 at 4:15 PM, Andrew Morton
    <akpm@linux-foundation.org> wrote:
    > On Tue, 23 Nov 2010 15:05:39 +0900 Minchan Kim <minchan.kim@gmail.com> wrote:
    >
    >> On Tue, Nov 23, 2010 at 2:48 PM, Andrew Morton
    >> >> > move it to the head of the LRU anyway. __But given that the user has
    >> >>
    >> >> Why does it move into head of LRU?
    >> >> If the page which isn't mapped doesn't have PG_referenced, it would be
    >> >> reclaimed.
    >> >
    >> > If it's dirty or under writeback it can't be reclaimed!
    >>
    >> I see your point. And it's why I add it to head of inactive list.
    >
    > But that *guarantees* that the page will get a full trip around the
    > inactive list.  And this will guarantee that potentially useful pages
    > are reclaimed before the pages which we *know* the user doesn't want!
    > Bad!
    >
    > Whereas if we queue it to the tail, it will only get that full trip if
    > reclaim happens to run before the page is cleaned.  And we just agreed
    > that reclaim isn't likely to run immediately, because pages are being
    > freed.
    >
    > So we face a choice between guaranteed eviction of potentially-useful
    > pages (which are very expensive to reestablish) versus a *possible*
    > need to move an unreclaimable page to the head of the LRU, which is
    > cheap.

    How about flagging SetPageReclaim when we add it to head of inactive?
    If page write is complete, end_page_writeback would move it to tail of
    inactive.

    --
    Kind regards,
    Minchan Kim
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