ao? 2011a1'06ae??21ae?JPY 17:36, Mel Gorman a??e??:
 >

Fragmentation avoidance benefits from tuning min_free_kbytes to a higher
value and minimising fragmentation-related problems is crucial if THP is
to allocate its necessary pages.

THP tunes min_free_kbytes automatically and this value is in part
related to the number of zones. At 512M on a single node machine, the
recommended min_free_kbytes is close to 10% of memory which is barely
tolerable as it is. At 256M, it's 17%, at 128M, it's 34% so tuning the
value lower has diminishing returns as the performance impact of giving
up such a high percentage of free memory is not going to be offset by
reduced TLB misses. Tuning it to a higher value might make some sense
if the higher min_free_kbytes was a problem but it would be much more
rational to tune it as a sysctl than making it a compile-time decision.

What this patch changed is the check of total memory pages in hugepage_init(),
which I don't think is suitable as a sysctl.

If you mean min_free_kbytes could be tuned as a sysctl, that should be done
in other patch, right? :)

Thanks.

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