On Mon, 9 May 2022 08:47:10 -0700 Minchan Kim <minchan@xxxxxxxxxx> wrote: > The rmap locks(i_mmap_rwsem and anon_vma->root->rwsem) could be > contented under memory pressure if processes keep working on > their vmas(e.g., fork, mmap, munmap). It makes reclaim path > stuck. In our real workload traces, we see kswapd is waiting the > lock for 300ms+(a sec as worst case) and it makes other processes > entering direct reclaim, which were also stuck on the lock. > > This patch makes LRU aging path try_lock mode like shink_page_list > so the reclaim context will keep working with next LRU pages > without being stuck. > > Since this patch introduces a new "contended" field as out-param > along with try_lock in-param in rmap_walk_control, it's not > immutable any longer if the try_lock is set so remove const > keywords on rmap related functions. Since rmap walking is already > expensive operation, I doubt the const would help sizable benefit( > And we didn't have it until 5.17). Some quantitative testing results would be helpful. Demonstrate the benefits of the patch?
