> > > > V1 did compaction per pageblock. but current patch doesn't. > > > > so, Is COMPACTBLOCKS still good name? > > > > > > It's not such a minor nit. I wondered about that myself but it's still a > > > block - just not a pageblock. Would COMPACTCLUSTER be a better name as it's > > > related to COMPACT_CLUSTER_MAX? > > > > I've looked at this code again. honestly I'm a abit confusing even though both your > > suggestions seems reasonable. > > > > now COMPACTBLOCKS is tracking #-of-called-migrate_pages. but I can't imazine > > how to use it. can you please explain this ststics purpose? probably this is only useful > > when conbination other stats, and the name should be consist with such combination one. > > > > It is intended to count how many steps compaction took, the fewer the > better so minimally, the lower this number is the better. Specifically, the > "goodness" is related to the number of pages that were successfully allocated > due to compaction. Assuming the only high-order allocation was huge pages, > one possible calculation for "goodness" is; > > hugepage_clusters = (1 << HUGE HUGETLB_PAGE_ORDER) / COMPACT_CLUSTER_MAX > goodness = (compactclusters / hugepage_clusters) / compactsuccess > > The value of goodness is undefined if "compactsuccess" is 0. > > Otherwise, the closer the "goodness" is to 1, the better. A value of 1 > implies that compaction is selecting exactly the right blocks for migration > and the minimum number of pages are being moved around. The greater the value, > the more "useless" work compaction is doing. > > If there are a mix of high-orders that are resulting in compaction, calculating > the goodness is a lot harder and compactcluster is just a rule of thumb as > to how much work compaction is doing. > > Does that make sense? Sure! then, now I fully agree with COMPACTCLUSTER. Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>