mm: numa: Scan pages with elevated page_mapcount

i/linux

Currently automatic NUMA balancing is unable to distinguish between false
shared versus private pages except by ignoring pages with an elevated
page_mapcount entirely. This avoids shared pages bouncing between the
nodes whose task is using them but that is ignored quite a lot of data.

This patch kicks away the training wheels in preparation for adding support
for identifying shared/private pages is now in place. The ordering is so
that the impact of the shared/private detection can be easily measured. Note
that the patch does not migrate shared, file-backed within vmas marked
VM_EXEC as these are generally shared library pages. Migrating such pages
is not beneficial as there is an expectation they are read-shared between
caches and iTLB and iCache pressure is generally low.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-28-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

This commit is contained in:

Mel Gorman

2013-10-07 11:29:05 +01:00

committed by

Ingo Molnar

parent 9ff1d9ff3c

commit 1bc115d87d

5 changed files with 18 additions and 29 deletions

									
										mm/mprotect.c
									
		+1
		-3
	
												View File
												
				@@ -69,9 +69,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,

									if (last_nid != this_nid)

										all_same_node = false;

									/* only check non-shared pages */

									if (!pte_numa(oldpte) &&

									    page_mapcount(page) == 1) {

									if (!pte_numa(oldpte)) {

										ptent = pte_mknuma(ptent);

										updated = true;

									}