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authorShakeel Butt <shakeelb@google.com>2017-11-15 17:38:26 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-11-15 18:21:07 -0800
commit72b03fcd5d515441d4aefcad01c1c4392c8099c9 (patch)
treed96a20e332ed3f147ef4431c5e410205fc376e9a /mm
parent4518085e127dff97e74f74a8780d7564e273bec8 (diff)
download96b-common-72b03fcd5d515441d4aefcad01c1c4392c8099c9.tar.gz
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 <shakeelb@google.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Balbir Singh <bsingharora@gmail.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Yisheng Xie <xieyisheng1@huawei.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Greg Thelen <gthelen@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/mlock.c5
1 files changed, 0 insertions, 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;