Recently we have observed high latency in mlock() in our generic library and noticed that users have started using tmpfs files even without swap and the latency was due to expensive remote LRU cache draining. Is lru_add_drain_all() required by mlock()? The answer is no and the reason it is still in mlock() is to rapidly move mlocked pages to unevictable LRU. Without lru_add_drain_all() the mlocked pages which were on pagevec at mlock() time will be moved to evictable LRUs but will eventually be moved back to unevictable LRU by reclaim. So, we can safely remove lru_add_drain_all() from mlock(). Also there is no need for local lru_add_drain() as it will be called deep inside __mm_populate() (in follow_page_pte()). Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx> --- mm/mlock.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/mm/mlock.c b/mm/mlock.c index dfc6f1912176..3ceb2935d1e0 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -669,8 +669,6 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla if (!can_do_mlock()) return -EPERM; - lru_add_drain_all(); /* flush pagevec */ - len = PAGE_ALIGN(len + (offset_in_page(start))); start &= PAGE_MASK; @@ -797,9 +795,6 @@ SYSCALL_DEFINE1(mlockall, int, flags) if (!can_do_mlock()) return -EPERM; - if (flags & MCL_CURRENT) - lru_add_drain_all(); /* flush pagevec */ - lock_limit = rlimit(RLIMIT_MEMLOCK); lock_limit >>= PAGE_SHIFT; -- 2.15.0.rc1.287.g2b38de12cc-goog -- 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>
