tree d96a20e332ed3f147ef4431c5e410205fc376e9a
parent 4518085e127dff97e74f74a8780d7564e273bec8
author Shakeel Butt <shakeelb@google.com> 1510796306 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> 1510798867 -0800

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>