From 72b03fcd5d515441d4aefcad01c1c4392c8099c9 Mon Sep 17 00:00:00 2001 From: Shakeel Butt Date: Wed, 15 Nov 2017 17:38:26 -0800 Subject: [PATCH] mm: mlock: remove lru_add_drain_all() 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. If anything lru_add_drain_all() should be called _after_ pages have been mlocked and faulted in but even that is not strictly needed because those pages would get to the appropriate LRUs lazily during the reclaim path. Moreover follow_page_pte (gup) will drain the local pcp LRU cache. 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. [mhocko@suse.com: changelog fix] Link: http://lkml.kernel.org/r/20171019222507.2894-1-shakeelb@google.com Signed-off-by: Shakeel Butt Acked-by: Michal Hocko Acked-by: Balbir Singh Acked-by: Vlastimil Babka Cc: "Kirill A. Shutemov" Cc: Joonsoo Kim Cc: Minchan Kim Cc: Yisheng Xie Cc: Ingo Molnar Cc: Greg Thelen Cc: Hugh Dickins Cc: Anshuman Khandual Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mlock.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/mm/mlock.c b/mm/mlock.c index ed37cb208d19..30472d438794 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -670,8 +670,6 @@ 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; @@ -798,9 +796,6 @@ 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; -- 2.30.2