lkml.org 
[lkml]   [2013]   [Jul]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 04/18] mm: numa: Do not migrate or account for hinting faults on the zero page
Date
The zero page is not replicated between nodes and is often shared
between processes. The data is read-only and likely to be cached in
local CPUs if heavily accessed meaning that the remote memory access
cost is less of a concern. This patch stops accounting for numa hinting
faults on the zero page in both terms of counting faults and scheduling
tasks on nodes.

Signed-off-by: Mel Gorman <mgorman@suse.de>
---
mm/huge_memory.c | 9 +++++++++
mm/memory.c | 7 ++++++-
2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e4a79fa..ec938ed 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1302,6 +1302,15 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,

page = pmd_page(pmd);
get_page(page);
+
+ /*
+ * Do not account for faults against the huge zero page. The read-only
+ * data is likely to be read-cached on the local CPUs and it is less
+ * useful to know about local versus remote hits on the zero page.
+ */
+ if (is_huge_zero_pfn(page_to_pfn(page)))
+ goto clear_pmdnuma;
+
src_nid = numa_node_id();
count_vm_numa_event(NUMA_HINT_FAULTS);
if (src_nid == page_to_nid(page))
diff --git a/mm/memory.c b/mm/memory.c
index ba94dec..6c6f6b0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3560,8 +3560,13 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
set_pte_at(mm, addr, ptep, pte);
update_mmu_cache(vma, addr, ptep);

+ /*
+ * Do not account for faults against the zero page. The read-only data
+ * is likely to be read-cached on the local CPUs and it is less useful
+ * to know about local versus remote hits on the zero page.
+ */
page = vm_normal_page(vma, addr, pte);
- if (!page) {
+ if (!page || is_zero_pfn(page_to_pfn(page))) {
pte_unmap_unlock(ptep, ptl);
return 0;
}
--
1.8.1.4


\
 
 \ /
  Last update: 2013-07-16 00:21    [W:0.371 / U:36.508 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site