Re: [PATCH 1/2] mm/pageblock: mitigation cmpxchg false sharing in pageblock flags

[David Hildenbrand]

On 16.08.20 05:47, Alex Shi wrote:
> pageblock_flags is used as long, since every pageblock_flags is just 4
> bits, 'long' size will include 8(32bit machine) or 16 pageblocks' flags,
> that flag setting has to sync in cmpxchg with 7 or 15 other pageblock
> flags. It would cause long waiting for sync.
> 
> If we could change the pageblock_flags variable as char, we could use
> char size cmpxchg, which just sync up with 2 pageblock flags. it could
> relief much false sharing in cmpxchg.

Do you have any performance numbers to back your claims? IOW, do we care
at all?



-- 
Thanks,

David / dhildenb