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    SubjectRe: [PATCH 3/3] compaction accouting fix
    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.
    > 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.
    > CC: Mel Gorman <>
    > CC: Johannes Weiner <>
    > CC: Rik van Riel <>
    > Signed-off-by: Minchan Kim <>

    Acked-by: Johannes Weiner <>

    It's a teensy-bit awkward that isolate_migratepages() can return
    success without actually isolating any new pages, just because there
    are still some pages left from a previous run (cc->nr_migratepages is
    maintained across isolation calls).

    Maybe isolate_migratepages() should just return an error if compaction
    should really be aborted and 0 otherwise, and have compact_zone()
    always check for cc->nr_migratepages itself?

    if (isolate_migratepages(zone, cc) < 0) {
    goto out;

    if (!cc->nr_migratepages)


    Just a nit-pick, though. If you don't agree, just leave it as is.

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      Last update: 2011-08-31 13:39    [W:0.022 / U:0.284 seconds]
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