On 06/26/2015 04:14 AM, Joonsoo Kim wrote:
2015-06-26 3:56 GMT+09:00 Vlastimil Babka <vbabka@xxxxxxx>:
on non-movable would be maintained so fallback doesn't happen.
There's nothing that guarantees that the migration scanner will be emptying
unmovable pageblock, or am I missing something?
As replied to Mel's comment, as number of unmovable pageblocks, which is
filled by movable pages due to this compaction change increases,
possible candidate reclaimable/migratable pages from them also increase.
So, at some time, amount of used page by free scanner and amount of
migrated page by migration scanner would be balanced.
Worse, those pageblocks would be
marked to skip by the free scanner if it isolated free pages from them, so
migration scanner would skip them.
Yes, but, next iteration will move out movable pages from that pageblock
and freed pages will be used for further unmovable allocation.
So, in the long term, this doesn't make much more fragmentation.
Theoretically, maybe. I guess there's not much point discussing it
further, until there's data from experiments evaluating the long-term
fragmentation (think of e.g. the number of mixed pageblocks you already
checked in different experiments).
Thanks.
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