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    SubjectRe: [PATCH v3 5/7] mm/compaction: respect compaction order when updating defer counter
    On Fri, Dec 04, 2015 at 06:15:02PM +0100, Vlastimil Babka wrote:
    > On 12/03/2015 08:11 AM, Joonsoo Kim wrote:
    > >It doesn't make sense that we reset defer counter
    > >in compaction_defer_reset() when compaction request under the order of
    > >compact_order_failed succeed. Fix it.
    >
    > Right.
    >
    > >And, it does make sense that giving enough chance for updated failed
    > >order compaction before deferring. Change it.
    >
    > Sorry, can't understand the meaning here. From the code it seems
    > that you want to reset defer_shift to 0 instead of increasing it,
    > when the current order is lower than the failed one? That makes
    > sense, yeah.

    You correctly understand my intention. :)

    > How about this?
    >
    > "On the other hand, when deferring compaction for an order lower
    > than the current compact_order_failed, we can assume the lower order
    > will recover more quickly, so we should reset the progress made
    > previously on compact_defer_shift with the higher order."

    Will add it.

    >
    > >Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    >
    > Acked-by: Vlastimil Babka <vbabka@suse.cz>

    Thanks.
    >
    > >---
    > > mm/compaction.c | 19 +++++++++++--------
    > > 1 file changed, 11 insertions(+), 8 deletions(-)
    > >
    > >diff --git a/mm/compaction.c b/mm/compaction.c
    > >index 67b8d90..1a75a6e 100644
    > >--- a/mm/compaction.c
    > >+++ b/mm/compaction.c
    > >@@ -126,11 +126,14 @@ static struct page *pageblock_pfn_to_page(unsigned long start_pfn,
    > > */
    > > static void defer_compaction(struct zone *zone, int order)
    > > {
    > >- zone->compact_considered = 0;
    > >- zone->compact_defer_shift++;
    > >-
    > >- if (order < zone->compact_order_failed)
    > >+ if (order < zone->compact_order_failed) {
    > >+ zone->compact_considered = 0;
    > >+ zone->compact_defer_shift = 0;
    > > zone->compact_order_failed = order;
    > >+ } else {
    > >+ zone->compact_considered = 0;
    > >+ zone->compact_defer_shift++;
    > >+ }
    > >
    > > if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
    > > zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
    > >@@ -161,11 +164,11 @@ bool compaction_deferred(struct zone *zone, int order)
    > > /* Update defer tracking counters after successful compaction of given order */
    > > static void compaction_defer_reset(struct zone *zone, int order)
    > > {
    > >- zone->compact_considered = 0;
    > >- zone->compact_defer_shift = 0;
    > >-
    > >- if (order >= zone->compact_order_failed)
    > >+ if (order >= zone->compact_order_failed) {
    > >+ zone->compact_considered = 0;
    > >+ zone->compact_defer_shift = 0;
    > > zone->compact_order_failed = order + 1;
    > >+ }
    > >
    > > trace_mm_compaction_defer_reset(zone, order);
    > > }
    > >
    >
    > --
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