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mm: numa: Scan pages with elevated page_mapcount

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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
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12
mm/huge_memory.c
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@@ -1484,14 +1484,12 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
struct page *page = pmd_page(*pmd);
/*
* Only check non-shared pages. Do not trap faults
* against the zero page. The read-only data is likely
* to be read-cached on the local CPU cache and it is
* less useful to know about local vs remote hits on
* the zero page.
* Do not trap faults against the zero page. The
* read-only data is likely to be read-cached on the
* local CPU cache and it is less useful to know about
* local vs remote hits on the zero page.
*/
if (page_mapcount(page) == 1 &&
!is_huge_zero_page(page) &&
if (!is_huge_zero_page(page) &&
!pmd_numa(*pmd)) {
entry = pmdp_get_and_clear(mm, addr, pmd);
entry = pmd_mknuma(entry);