The patch titled
Subject: mm: unrig VMA cache hit ratio
has been added to the -mm tree. Its filename is
mm-unrig-vma-cache-hit-ratio.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-unrig-vma-cache-hit-ratio.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-unrig-vma-cache-hit-ratio.patch
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------------------------------------------------------
From: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Subject: mm: unrig VMA cache hit ratio
Current code doesn't count first FIND operation after VMA cache flush
(which happen surprisingly often) artificially increasing cache hit ratio.
On my regular setup the difference is:
Before After
==========================================================
* boot, login into KDE
vmacache_find_calls 446216 vmacache_find_calls 492741
vmacache_find_hits 277596 vmacache_find_hits 276096
~62.2% ~56.0%
* rebuild kernel (no changes to code, usual config)
vmacache_find_calls 1943007 vmacache_find_calls 2083718
vmacache_find_hits 1246123 vmacache_find_hits 1244146
~64.1% ~59.7%
* rebuild kernel (full rebuild, usual config)
vmacache_find_calls 32163155 vmacache_find_calls 33677183
vmacache_find_hits 27889956 vmacache_find_hits 27877591
~88.2% ~84.3%
Total: ~4% cache hit ratio.
If someone is counting _relative_ cache _miss_ ratio, misreporting is much
higher.
Link: http://lkml.kernel.org/r/20160822225009.GA3934@xxxxxxxxxxxxxxx
Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/vmacache.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff -puN mm/vmacache.c~mm-unrig-vma-cache-hit-ratio mm/vmacache.c
--- a/mm/vmacache.c~mm-unrig-vma-cache-hit-ratio
+++ a/mm/vmacache.c
@@ -87,11 +87,11 @@ struct vm_area_struct *vmacache_find(str
{
int i;
+ count_vm_vmacache_event(VMACACHE_FIND_CALLS);
+
if (!vmacache_valid(mm))
return NULL;
- count_vm_vmacache_event(VMACACHE_FIND_CALLS);
-
for (i = 0; i < VMACACHE_SIZE; i++) {
struct vm_area_struct *vma = current->vmacache[i];
@@ -115,11 +115,11 @@ struct vm_area_struct *vmacache_find_exa
{
int i;
+ count_vm_vmacache_event(VMACACHE_FIND_CALLS);
+
if (!vmacache_valid(mm))
return NULL;
- count_vm_vmacache_event(VMACACHE_FIND_CALLS);
-
for (i = 0; i < VMACACHE_SIZE; i++) {
struct vm_area_struct *vma = current->vmacache[i];
_
Patches currently in -mm which might be from adobriyan@xxxxxxxxx are
kbuild-simpler-generation-of-assembly-constants.patch
mm-unrig-vma-cache-hit-ratio.patch
proc-much-faster-proc-vmstat.patch
proc-faster-proc-status.patch
cred-simpler-1d-supplementary-groups.patch
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