mm: Do not drain pagevecs for mlockall(MCL_FUTURE)

[Christoph Lameter <cl@xxxxxxxxxx>]

MCL_FUTURE does not move pages between lru list and draining the LRU per
cpu pagevecs is a nasty activity. Avoid doing it unecessarily.

Signed-off-by: Christoph Lameter <cl@xxxxxxxxxx>


---
 mm/mlock.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-2.6/mm/mlock.c
===================================================================
--- linux-2.6.orig/mm/mlock.c	2011-10-07 14:57:52.000000000 -0500
+++ linux-2.6/mm/mlock.c	2011-10-07 15:01:06.000000000 -0500
@@ -549,7 +549,8 @@ SYSCALL_DEFINE1(mlockall, int, flags)
 	if (!can_do_mlock())
 		goto out;

-	lru_add_drain_all();	/* flush pagevec */
+	if (flags & MCL_CURRENT)
+		lru_add_drain_all();	/* flush pagevec */

 	down_write(&current->mm->mmap_sem);

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