diff options
| author | Alexey Dobriyan <adobriyan@gmail.com> | 2016-10-07 16:58:39 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-10-07 18:46:27 -0700 |
| commit | 131ddc5c7d814d61f945b6322019e5148f6d39f0 (patch) | |
| tree | 757cd259f035f9bf8f0efc477b0e3e6e5aa935f0 | |
| parent | f7e2355f0f8635ddcfd26858f58732b7bf85f9f4 (diff) | |
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@p183.telecom.by
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/vmacache.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/mm/vmacache.c b/mm/vmacache.c index fd09dc9c6812..035fdeb35b43 100644 --- a/mm/vmacache.c +++ b/mm/vmacache.c @@ -87,11 +87,11 @@ struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr) { 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_exact(struct mm_struct *mm, { 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]; |