lru_add_drain_all() is not required by mlock() and it will drain everything that has been cached at the time mlock is called. And that is not really related to the memory which will be faulted in (and cached) and mlocked by the syscall itself. Without lru_add_drain_all() the mlocked pages can remain on pagevecs and be moved to evictable LRUs. However they will eventually be moved back to unevictable LRU by reclaim. So, we can safely remove lru_add_drain_all() from mlock syscall. Also there is no need for local lru_add_drain() as it will be called deep inside __mm_populate() (in follow_page_pte()). On larger machines the overhead of lru_add_drain_all() in mlock() can be significant when mlocking data already in memory. We have observed high latency in mlock() due to lru_add_drain_all() when the users were mlocking in memory tmpfs files. Signed-off-by: Shakeel Butt <shakeelb@xxxxxxxxxx> --- Changelog since v1: - updated commit message 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.rc0.271.g36b669edcc-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>
