Hi Andrew, With all patches are acked-by Hugh and Johannes, and full testing from LKP, is this patchset ready for more testing on linux-next? or anything still need be improved? Thanks Alex 在 2020/11/5 下午4:55, Alex Shi 写道: > This version rebase on next/master 20201104, with much of Johannes's > Acks and some changes according to Johannes comments. And add a new patch > v21-0006-mm-rmap-stop-store-reordering-issue-on-page-mapp.patch to support > v21-0007. > > This patchset followed 2 memcg VM_WARN_ON_ONCE_PAGE patches which were > added to -mm tree yesterday. > > Many thanks for line by line review by Hugh Dickins, Alexander Duyck and > Johannes Weiner. > > So now this patchset includes 3 parts: > 1, some code cleanup and minimum optimization as a preparation. > 2, use TestCleanPageLRU as page isolation's precondition. > 3, replace per node lru_lock with per memcg per node lru_lock. > > Current lru_lock is one for each of node, pgdat->lru_lock, that guard for > lru lists, but now we had moved the lru lists into memcg for long time. Still > using per node lru_lock is clearly unscalable, pages on each of memcgs have > to compete each others for a whole lru_lock. This patchset try to use per > lruvec/memcg lru_lock to repleace per node lru lock to guard lru lists, make > it scalable for memcgs and get performance gain. > > Currently lru_lock still guards both lru list and page's lru bit, that's ok. > but if we want to use specific lruvec lock on the page, we need to pin down > the page's lruvec/memcg during locking. Just taking lruvec lock first may be > undermined by the page's memcg charge/migration. To fix this problem, we could > take out the page's lru bit clear and use it as pin down action to block the > memcg changes. That's the reason for new atomic func TestClearPageLRU. > So now isolating a page need both actions: TestClearPageLRU and hold the > lru_lock. > > The typical usage of this is isolate_migratepages_block() in compaction.c > we have to take lru bit before lru lock, that serialized the page isolation > in memcg page charge/migration which will change page's lruvec and new > lru_lock in it. > > The above solution suggested by Johannes Weiner, and based on his new memcg > charge path, then have this patchset. (Hugh Dickins tested and contributed much > code from compaction fix to general code polish, thanks a lot!). > > Daniel Jordan's testing show 62% improvement on modified readtwice case > on his 2P * 10 core * 2 HT broadwell box on v18, which has no much different > with this v20. > https://lore.kernel.org/lkml/20200915165807.kpp7uhiw7l3loofu@xxxxxxxxxxxxxxxxxxxxxxxxxx/ > > Thanks Hugh Dickins and Konstantin Khlebnikov, they both brought this > idea 8 years ago, and others who give comments as well: Daniel Jordan, > Mel Gorman, Shakeel Butt, Matthew Wilcox, Alexander Duyck etc. > > Thanks for Testing support from Intel 0day and Rong Chen, Fengguang Wu, > and Yun Wang. Hugh Dickins also shared his kbuild-swap case. Thanks!
