Subject: + mm-slub-fix-alloc_slowpath-stat.patch added to -mm tree
To: dave.hansen@xxxxxxxxxxxxxxx,cl@xxxxxxxxx,penberg@xxxxxxxxxx,rientjes@xxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Thu, 08 May 2014 15:56:00 -0700
The patch titled
Subject: mm: slub: fix ALLOC_SLOWPATH stat
has been added to the -mm tree. Its filename is
mm-slub-fix-alloc_slowpath-stat.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-slub-fix-alloc_slowpath-stat.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-slub-fix-alloc_slowpath-stat.patch
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From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Subject: mm: slub: fix ALLOC_SLOWPATH stat
There used to be only one path out of __slab_alloc(), and ALLOC_SLOWPATH
got bumped in that exit path. Now there are two, and a bunch of gotos.
ALLOC_SLOWPATH can now get set more than once during a single call to
__slab_alloc() which is pretty bogus. Here's the sequence:
1. Enter __slab_alloc(), fall through all the way to the
stat(s, ALLOC_SLOWPATH);
2. hit 'if (!freelist)', and bump DEACTIVATE_BYPASS, jump to
new_slab (goto #1)
3. Hit 'if (c->partial)', bump CPU_PARTIAL_ALLOC, goto redo
(goto #2)
4. Fall through in the same path we did before all the way to
stat(s, ALLOC_SLOWPATH)
5. bump ALLOC_REFILL stat, then return
Doing this is obviously bogus. It keeps us from being able to accurately
compare ALLOC_SLOWPATH vs. ALLOC_FASTPATH. It also means that the total
number of allocs always exceeds the total number of frees.
This patch moves stat(s, ALLOC_SLOWPATH) to be called from the same place
that __slab_alloc() is. This makes it much less likely that
ALLOC_SLOWPATH will get botched again in the spaghetti-code inside
__slab_alloc().
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Acked-by: Christoph Lameter <cl@xxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff -puN mm/slub.c~mm-slub-fix-alloc_slowpath-stat mm/slub.c
--- a/mm/slub.c~mm-slub-fix-alloc_slowpath-stat
+++ a/mm/slub.c
@@ -2326,8 +2326,6 @@ redo:
if (freelist)
goto load_freelist;
- stat(s, ALLOC_SLOWPATH);
-
freelist = get_freelist(s, page);
if (!freelist) {
@@ -2432,10 +2430,10 @@ redo:
object = c->freelist;
page = c->page;
- if (unlikely(!object || !node_match(page, node)))
+ if (unlikely(!object || !node_match(page, node))) {
object = __slab_alloc(s, gfpflags, node, addr, c);
-
- else {
+ stat(s, ALLOC_SLOWPATH);
+ } else {
void *next_object = get_freepointer_safe(s, object);
/*
_
Patches currently in -mm which might be from dave.hansen@xxxxxxxxxxxxxxx are
mm-slub-fix-alloc_slowpath-stat.patch
mm-introduce-do_shared_fault-and-drop-do_fault-fix-fix.patch
mm-pass-vm_bug_on-reason-to-dump_page.patch
mm-pass-vm_bug_on-reason-to-dump_page-fix.patch
mm-debug-make-bad_range-output-more-usable-and-readable.patch
mm-shrinker-trace-points-fix-negatives.patch
mm-shrinker-add-nid-to-tracepoint-output.patch
do_shared_fault-check-that-mmap_sem-is-held.patch
linux-next.patch
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