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    SubjectRe: [PATCH 07/11] Memory compaction core
    Date
    > > > > V1 did compaction per pageblock. but current patch doesn't.
    > > > > so, Is COMPACTBLOCKS still good name?
    > > >
    > > > It's not such a minor nit. I wondered about that myself but it's still a
    > > > block - just not a pageblock. Would COMPACTCLUSTER be a better name as it's
    > > > related to COMPACT_CLUSTER_MAX?
    > >
    > > I've looked at this code again. honestly I'm a abit confusing even though both your
    > > suggestions seems reasonable.
    > >
    > > now COMPACTBLOCKS is tracking #-of-called-migrate_pages. but I can't imazine
    > > how to use it. can you please explain this ststics purpose? probably this is only useful
    > > when conbination other stats, and the name should be consist with such combination one.
    > >
    >
    > It is intended to count how many steps compaction took, the fewer the
    > better so minimally, the lower this number is the better. Specifically, the
    > "goodness" is related to the number of pages that were successfully allocated
    > due to compaction. Assuming the only high-order allocation was huge pages,
    > one possible calculation for "goodness" is;
    >
    > hugepage_clusters = (1 << HUGE HUGETLB_PAGE_ORDER) / COMPACT_CLUSTER_MAX
    > goodness = (compactclusters / hugepage_clusters) / compactsuccess
    >
    > The value of goodness is undefined if "compactsuccess" is 0.
    >
    > Otherwise, the closer the "goodness" is to 1, the better. A value of 1
    > implies that compaction is selecting exactly the right blocks for migration
    > and the minimum number of pages are being moved around. The greater the value,
    > the more "useless" work compaction is doing.
    >
    > If there are a mix of high-orders that are resulting in compaction, calculating
    > the goodness is a lot harder and compactcluster is just a rule of thumb as
    > to how much work compaction is doing.
    >
    > Does that make sense?

    Sure! then, now I fully agree with COMPACTCLUSTER.

    Thanks.




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