* [PATCH] mm: slub: fix ALLOC_SLOWPATH stat
@ 2014-01-06 20:43 Dave Hansen
2014-01-07 2:44 ` Christoph Lameter
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Dave Hansen @ 2014-01-06 20:43 UTC (permalink / raw)
To: linux-mm; +Cc: linux-kernel, cl, akpm, penberg, Dave Hansen
From: Dave Hansen <dave.hansen@linux.intel.com>
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@linux.intel.com>
---
linux.git-davehans/mm/slub.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff -puN mm/slub.c~slub-ALLOC_SLOWPATH-stat mm/slub.c
--- linux.git/mm/slub.c~slub-ALLOC_SLOWPATH-stat 2014-01-06 12:39:28.148072544 -0800
+++ linux.git-davehans/mm/slub.c 2014-01-06 12:39:28.155072860 -0800
@@ -2301,8 +2301,6 @@ redo:
if (freelist)
goto load_freelist;
- stat(s, ALLOC_SLOWPATH);
-
freelist = get_freelist(s, page);
if (!freelist) {
@@ -2409,10 +2407,10 @@ 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);
/*
_
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: slub: fix ALLOC_SLOWPATH stat
2014-01-06 20:43 [PATCH] mm: slub: fix ALLOC_SLOWPATH stat Dave Hansen
@ 2014-01-07 2:44 ` Christoph Lameter
2014-01-07 4:44 ` Wanpeng Li
2014-01-09 2:24 ` David Rientjes
2 siblings, 0 replies; 6+ messages in thread
From: Christoph Lameter @ 2014-01-07 2:44 UTC (permalink / raw)
To: Dave Hansen; +Cc: linux-mm, linux-kernel, akpm, penberg
On Mon, 6 Jan 2014, Dave Hansen wrote:
> 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().
Acked-by: Christoph Lameter <cl@linux.com>
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: slub: fix ALLOC_SLOWPATH stat
2014-01-06 20:43 [PATCH] mm: slub: fix ALLOC_SLOWPATH stat Dave Hansen
2014-01-07 2:44 ` Christoph Lameter
@ 2014-01-07 4:44 ` Wanpeng Li
2014-01-09 2:24 ` David Rientjes
2 siblings, 0 replies; 6+ messages in thread
From: Wanpeng Li @ 2014-01-07 4:44 UTC (permalink / raw)
To: Dave Hansen; +Cc: linux-mm, linux-kernel, cl, akpm, penberg
On Mon, Jan 06, 2014 at 12:43:00PM -0800, Dave Hansen wrote:
>
>From: Dave Hansen <dave.hansen@linux.intel.com>
>
>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@linux.intel.com>
Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
>---
>
> linux.git-davehans/mm/slub.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
>diff -puN mm/slub.c~slub-ALLOC_SLOWPATH-stat mm/slub.c
>--- linux.git/mm/slub.c~slub-ALLOC_SLOWPATH-stat 2014-01-06 12:39:28.148072544 -0800
>+++ linux.git-davehans/mm/slub.c 2014-01-06 12:39:28.155072860 -0800
>@@ -2301,8 +2301,6 @@ redo:
> if (freelist)
> goto load_freelist;
>
>- stat(s, ALLOC_SLOWPATH);
>-
> freelist = get_freelist(s, page);
>
> if (!freelist) {
>@@ -2409,10 +2407,10 @@ 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);
>
> /*
>_
>
>--
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: slub: fix ALLOC_SLOWPATH stat
2014-01-06 20:43 [PATCH] mm: slub: fix ALLOC_SLOWPATH stat Dave Hansen
2014-01-07 2:44 ` Christoph Lameter
2014-01-07 4:44 ` Wanpeng Li
@ 2014-01-09 2:24 ` David Rientjes
2014-01-21 22:14 ` David Rientjes
2 siblings, 1 reply; 6+ messages in thread
From: David Rientjes @ 2014-01-09 2:24 UTC (permalink / raw)
To: Dave Hansen; +Cc: linux-mm, linux-kernel, cl, akpm, penberg
On Mon, 6 Jan 2014, Dave Hansen wrote:
> 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@linux.intel.com>
Acked-by: David Rientjes <rientjes@google.com>
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: slub: fix ALLOC_SLOWPATH stat
2014-01-09 2:24 ` David Rientjes
@ 2014-01-21 22:14 ` David Rientjes
2014-05-08 3:05 ` David Rientjes
0 siblings, 1 reply; 6+ messages in thread
From: David Rientjes @ 2014-01-21 22:14 UTC (permalink / raw)
To: Dave Hansen
Cc: linux-mm, linux-kernel, Christoph Lameter, Andrew Morton, Pekka Enberg
On Wed, 8 Jan 2014, David Rientjes wrote:
> > 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@linux.intel.com>
>
> Acked-by: David Rientjes <rientjes@google.com>
>
Pekka, are you going to pick this up for linux-next? I think it would be
nice to have for 3.14 for those of us who use the stats.
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: slub: fix ALLOC_SLOWPATH stat
2014-01-21 22:14 ` David Rientjes
@ 2014-05-08 3:05 ` David Rientjes
0 siblings, 0 replies; 6+ messages in thread
From: David Rientjes @ 2014-05-08 3:05 UTC (permalink / raw)
To: Andrew Morton, Pekka Enberg
Cc: Dave Hansen, linux-mm, linux-kernel, Christoph Lameter
On Tue, 21 Jan 2014, David Rientjes wrote:
> On Wed, 8 Jan 2014, David Rientjes wrote:
>
> > > 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@linux.intel.com>
> >
> > Acked-by: David Rientjes <rientjes@google.com>
> >
>
> Pekka, are you going to pick this up for linux-next? I think it would be
> nice to have for 3.14 for those of us who use the stats.
>
Ping #2. Pekka or Andrew, would you pick this up for linux-next?
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2014-01-06 20:43 [PATCH] mm: slub: fix ALLOC_SLOWPATH stat Dave Hansen
2014-01-07 2:44 ` Christoph Lameter
2014-01-07 4:44 ` Wanpeng Li
2014-01-09 2:24 ` David Rientjes
2014-01-21 22:14 ` David Rientjes
2014-05-08 3:05 ` David Rientjes
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