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    SubjectRe: [PATCH 3/3] compaction accouting fix
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    On Thu, Sep 1, 2011 at 11:20 PM, Mel Gorman <mgorman@suse.de> wrote:
    > On Sun, Nov 13, 2011 at 01:37:43AM +0900, Minchan Kim wrote:
    >> I saw the following accouting of compaction during test of the series.
    >
    > s/accouting/accounting/ both here and in the subject. A nicer name the
    > patch would have been
    >
    > "mm: compaction: Only update compact_blocks_moved if compaction was successful"

    Thanks, I will fix it at next version. :)

    >
    >>
    >> compact_blocks_moved 251
    >> compact_pages_moved 44
    >>
    >> It's very awkward to me although it's possbile because it means we try to compact 251 blocks
    >> but it just migrated 44 pages. As further investigation, I found isolate_migratepages doesn't
    >> isolate any pages but it returns ISOLATE_SUCCESS and then, it just increases compact_blocks_moved
    >> but doesn't increased compact_pages_moved.
    >>
    >> This patch makes accouting of compaction works only in case of success of isolation.
    >>
    >
    > compact_blocks_moved exists to indicate the rate compaction is
    > scanning pageblocks. If compact_blocks_moved and compact_pages_moved
    > are increasing at a similar rate for example, it could imply that
    > compaction is doing a lot of scanning but is not necessarily useful
    > work. It's not necessarily reflected by compact_fail because that
    > counter is only updated for pages that were isolated from the LRU.

    You seem to say "compact_pagemigrate_failed" not "compact_fail".

    >
    > I now recognise of course that "compact_blocks_moved" was an *awful*
    > choice of name for this stat.

    I hope changing stat names as follows unless it's too late(ie, it
    doesn't break ABI with any tools)

    compact_blocks_moved -> compact_blocks
    compact_pages_moved -> compact_pgmigrated_success
    compact_pagemigrate_failed -> compact_pgmigrated_fail
    compact_stall -> compact_alloc_stall
    compact_fail -> compact_alloc_fail
    compact_success -> compact_alloc_success


    >
    > --
    > Mel Gorman
    > SUSE Labs
    >



    --
    Kind regards,
    Minchan Kim


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