在 2020/8/19 下午3:57, Anshuman Khandual 写道: > > > On 08/19/2020 11:17 AM, Alex Shi wrote: >> Current pageblock_flags is only 4 bits, so it has to share a char size >> in cmpxchg when get set, the false sharing cause perf drop. >> >> If we incrase the bits up to 8, false sharing would gone in cmpxchg. and >> the only cost is half char per pageblock, which is half char per 128MB >> on x86, 4 chars in 1 GB. > > Agreed that increase in memory utilization is negligible here but does > this really improve performance ? > It's no doubt in theory. and it would had a bad impact according to commit e380bebe4771548 mm, compaction: keep migration source private to a single but I do have some problem in running thpscale/mmtest. I'd like to see if anyone could give a try. BTW, I naturally hate the false sharing even it's in theory. Anyone who doesn't? :) Thanks Alex
