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authorMel Gorman <mgorman@suse.de>2013-10-07 11:29:05 +0100
committerIngo Molnar <mingo@kernel.org>2013-10-09 12:40:32 +0200
commit1bc115d87dffd1c43bdc3c9c9d1e3a51c195d18e (patch)
tree56a26b4f4fe089e3dd1df5a26877d1e4c0114d35 /mm
parent9ff1d9ff3c2c8ab3feaeb2e8056a07ca293f7bde (diff)
downloadlinux-1bc115d87dffd1c43bdc3c9c9d1e3a51c195d18e.tar.bz2
mm: numa: Scan pages with elevated page_mapcount
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>
Diffstat (limited to 'mm')
-rw-r--r--mm/huge_memory.c12
-rw-r--r--mm/memory.c7
-rw-r--r--mm/migrate.c17
-rw-r--r--mm/mprotect.c4
4 files changed, 14 insertions, 26 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 914216733e0a..2a28c2c6c165 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -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);
diff --git a/mm/memory.c b/mm/memory.c
index 24bc9b848af6..3e3b4b8b6c41 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3577,7 +3577,7 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
}
/* Migrate to the requested node */
- migrated = migrate_misplaced_page(page, target_nid);
+ migrated = migrate_misplaced_page(page, vma, target_nid);
if (migrated)
page_nid = target_nid;
@@ -3642,16 +3642,13 @@ static int do_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
page = vm_normal_page(vma, addr, pteval);
if (unlikely(!page))
continue;
- /* only check non-shared pages */
- if (unlikely(page_mapcount(page) != 1))
- continue;
last_nid = page_nid_last(page);
page_nid = page_to_nid(page);
target_nid = numa_migrate_prep(page, vma, addr, page_nid);
pte_unmap_unlock(pte, ptl);
if (target_nid != -1) {
- migrated = migrate_misplaced_page(page, target_nid);
+ migrated = migrate_misplaced_page(page, vma, target_nid);
if (migrated)
page_nid = target_nid;
} else {
diff --git a/mm/migrate.c b/mm/migrate.c
index 7bd90d3b16bb..fcba2f46bb80 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1599,7 +1599,8 @@ int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
* node. Caller is expected to have an elevated reference count on
* the page that will be dropped by this function before returning.
*/
-int migrate_misplaced_page(struct page *page, int node)
+int migrate_misplaced_page(struct page *page, struct vm_area_struct *vma,
+ int node)
{
pg_data_t *pgdat = NODE_DATA(node);
int isolated;
@@ -1607,10 +1608,11 @@ int migrate_misplaced_page(struct page *page, int node)
LIST_HEAD(migratepages);
/*
- * Don't migrate pages that are mapped in multiple processes.
- * TODO: Handle false sharing detection instead of this hammer
+ * Don't migrate file pages that are mapped in multiple processes
+ * with execute permissions as they are probably shared libraries.
*/
- if (page_mapcount(page) != 1)
+ if (page_mapcount(page) != 1 && page_is_file_cache(page) &&
+ (vma->vm_flags & VM_EXEC))
goto out;
/*
@@ -1661,13 +1663,6 @@ int migrate_misplaced_transhuge_page(struct mm_struct *mm,
int page_lru = page_is_file_cache(page);
/*
- * Don't migrate pages that are mapped in multiple processes.
- * TODO: Handle false sharing detection instead of this hammer
- */
- if (page_mapcount(page) != 1)
- goto out_dropref;
-
- /*
* Rate-limit the amount of data that is being migrated to a node.
* Optimal placement is no good if the memory bus is saturated and
* all the time is being spent migrating!
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 2da33dca6134..41e02923fcd9 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -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;
}