diff mbox series

[RFC,02/10] autonuma: Reduce cache footprint when scanning page tables

Message ID 20191101075727.26683-3-ying.huang@intel.com (mailing list archive)
State New, archived
Headers show
Series autonuma: Optimize memory placement in memory tiering system | expand

Commit Message

Huang, Ying Nov. 1, 2019, 7:57 a.m. UTC 
From: Huang Ying <ying.huang@intel.com>

In auto NUMA balancing page table scanning, if the pte_protnone() is
true, the PTE needs not to be changed because it's in target state
already.  So other checking on corresponding struct page is
unnecessary too.

So, if we check pte_protnone() firstly for each PTE, we can avoid
unnecessary struct page accessing, so that reduce the cache footprint
of NUMA balancing page table scanning.

In the performance test of pmbench memory accessing benchmark with
80:20 read/write ratio and normal access address distribution on a 2
socket Intel server with Optance DC Persistent Memory, perf profiling
shows that the autonuma page table scanning time reduces from 1.23% to
0.97% (that is, reduced 21%) with the patch.

Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
---
 mm/mprotect.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Comments

Mel Gorman Nov. 1, 2019, 11:13 a.m. UTC | #1 
On Fri, Nov 01, 2019 at 03:57:19PM +0800, Huang, Ying wrote:
> From: Huang Ying <ying.huang@intel.com>
> 
> In auto NUMA balancing page table scanning, if the pte_protnone() is
> true, the PTE needs not to be changed because it's in target state
> already.  So other checking on corresponding struct page is
> unnecessary too.
> 
> So, if we check pte_protnone() firstly for each PTE, we can avoid
> unnecessary struct page accessing, so that reduce the cache footprint
> of NUMA balancing page table scanning.
> 
> In the performance test of pmbench memory accessing benchmark with
> 80:20 read/write ratio and normal access address distribution on a 2
> socket Intel server with Optance DC Persistent Memory, perf profiling
> shows that the autonuma page table scanning time reduces from 1.23% to
> 0.97% (that is, reduced 21%) with the patch.
> 
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>

Acked-by: Mel Gorman <mgorman@suse.de>

This patch is independent of the series and should be resent separately.
Alternatively Andrew, please pick this patch up on its own.
diff mbox series

Patch

diff --git a/mm/mprotect.c b/mm/mprotect.c
index bf38dfbbb4b4..d69b9913388e 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -80,6 +80,10 @@  static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 			if (prot_numa) {
 				struct page *page;
 
+				/* Avoid TLB flush if possible */
+				if (pte_protnone(oldpte))
+					continue;
+
 				page = vm_normal_page(vma, addr, oldpte);
 				if (!page || PageKsm(page))
 					continue;
@@ -97,10 +101,6 @@  static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 				if (page_is_file_cache(page) && PageDirty(page))
 					continue;
 
-				/* Avoid TLB flush if possible */
-				if (pte_protnone(oldpte))
-					continue;
-
 				/*
 				 * Don't mess with PTEs if page is already on the node
 				 * a single-threaded process is running on.