On 11/23/2015 04:16 PM, Joonsoo Kim wrote:
> Numbers looks fine to me. I guess this performance degradation is
> caused by COMPACT_CLUSTER_MAX change (from 32 to 256). THP allocation
> is async so should be aborted quickly. But, after isolating 256
> migratable pages, it can't be aborted and will finish 256 pages
> migration (at least, current implementation).
> 
> Aaron, please test again with setting COMPACT_CLUSTER_MAX to 32
> (in swap.h)?

This is what I found in include/linux/swap.h:

#define SWAP_CLUSTER_MAX 32UL
#define COMPACT_CLUSTER_MAX SWAP_CLUSTER_MAX

Looks like it is already 32, or am I looking at the wrong place?

BTW, I'm using v4.3 for all these tests, and I just checked v4.4-rc2,
the above definition doesn't change.

> 
> And, please attach always-always's vmstat numbers, too.

Sure, attached the vmstat tool output, taken every second.

Thanks,
Aaron