On Thu, Sep 03, 2020 at 03:01:20PM +0800, 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 the false sharing in cmpxchg. > > Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> Page block types were not known to change at high frequency that would cause a measurable performance drop. If anything, the performance hit from pageblocks is the lookup paths which is a lot more frequent. What was the workload you were running that altered pageblocks at a high enough frequency for collisions to occur when updating adjacent pageblocks? -- Mel Gorman SUSE Labs
