On Wed, Jan 31, 2018 at 06:04:13PM -0500, daniel.m.jordan@xxxxxxxxxx wrote: > Now that release_pages is scaling better with concurrent removals from > the LRU, the performance results (included below) showed increased > contention on lru_lock in the add-to-LRU path. > > To alleviate some of this contention, do more work outside the LRU lock. > Prepare a local list of pages to be spliced onto the front of the LRU, > including setting PageLRU in each page, before taking lru_lock. Since > other threads use this page flag in certain checks outside lru_lock, > ensure each page's LRU links have been properly initialized before > setting the flag, and use memory barriers accordingly. > > Performance Results > > This is a will-it-scale run of page_fault1 using 4 different kernels. > > kernel kern # > > 4.15-rc2 1 > large-zone-batch 2 > lru-lock-base 3 > lru-lock-splice 4 > > Each kernel builds on the last. The first is a baseline, the second > makes zone->lock more scalable by increasing an order-0 per-cpu > pagelist's 'batch' and 'high' values to 310 and 1860 respectively Since the purpose of the patchset is to optimize lru_lock, you may consider adjusting pcp->high to be >= 32768(page_fault1's test size is 128M = 32768 pages). That should eliminate zone->lock contention entirely. > (courtesy of Aaron Lu's patch), the third scales lru_lock without > splicing pages (the previous patch in this series), and the fourth adds > page splicing (this patch). > > N tasks mmap, fault, and munmap anonymous pages in a loop until the test > time has elapsed. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
