[PATCH] mv clear node_load[] to __build_all_zonelists()‏

[PATCH] mv clear node_load[] to __build_all_zonelists()‏

[Bob Liu]

 If node_load[] is cleared everytime build_zonelists() is called,node_load[]
 will have no help to find the next node that should appear in the given node's
 fallback list.
 Signed-off-by: Bob Liu <bo-liu@hotmail.com>
---
 mm/page_alloc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d052abb..72f7345 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2544,7 +2544,6 @@ static void build_zonelists(pg_data_t *pgdat)
 	prev_node = local_node;
 	nodes_clear(used_mask);

-	memset(node_load, 0, sizeof(node_load));
 	memset(node_order, 0, sizeof(node_order));
 	j = 0;

@@ -2653,6 +2652,7 @@ static int __build_all_zonelists(void *dummy)
 {
 	int nid;

+	memset(node_load, 0, sizeof(node_load));
 	for_each_online_node(nid) {
 		pg_data_t *pgdat = NODE_DATA(nid);

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[PATCH] mv clear node_load[] to __build_all_zonelists()

[Bo Liu]

 If node_load[] is cleared everytime build_zonelists() is called,node_load[]
 will have no help to find the next node that should appear in the given node's
 fallback list.
 Signed-off-by: Bob Liu 
---
 mm/page_alloc.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d052abb..72f7345 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2544,7 +2544,6 @@ static void build_zonelists(pg_data_t *pgdat)
 	prev_node = local_node;
 	nodes_clear(used_mask);
 
-	memset(node_load, 0, sizeof(node_load));
 	memset(node_order, 0, sizeof(node_order));
 	j = 0;
 
@@ -2653,6 +2652,7 @@ static int __build_all_zonelists(void *dummy)
 {
 	int nid;
 
+	memset(node_load, 0, sizeof(node_load));
 	for_each_online_node(nid) {
 		pg_data_t *pgdat = NODE_DATA(nid);




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Re: [PATCH] mv clear node_load[] to __build_all_zonelists()

[KAMEZAWA Hiroyuki]

On Thu, 6 Aug 2009 18:44:40 +0800
Bo Liu <bo-liu@hotmail.com> wrote:

> 
>  If node_load[] is cleared everytime build_zonelists() is called,node_load[]
>  will have no help to find the next node that should appear in the given node's
>  fallback list.
>  Signed-off-by: Bob Liu 

nice catch. (my old bug...sorry

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

BTW, do you have special reasons to hide your mail address in commit log ?

I added proper CC: list.
Hmm, I think it's necessary to do total review/rewrite this function again..


> ---
>  mm/page_alloc.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>  
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index d052abb..72f7345 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2544,7 +2544,6 @@ static void build_zonelists(pg_data_t *pgdat)
>  	prev_node = local_node;
>  	nodes_clear(used_mask);
>  
> -	memset(node_load, 0, sizeof(node_load));
>  	memset(node_order, 0, sizeof(node_order));
>  	j = 0;
>  
> @@ -2653,6 +2652,7 @@ static int __build_all_zonelists(void *dummy)
>  {
>  	int nid;
>  
> +	memset(node_load, 0, sizeof(node_load));
>  	for_each_online_node(nid) {
>  		pg_data_t *pgdat = NODE_DATA(nid);
> 
> 
> 
> 
> _________________________________________________________________
> Drag na?? dropa??Get easy photo sharing with Windows Livea?c Photos.
> 
> http://www.microsoft.com/windows/windowslive/products/photos.aspx

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Re: [PATCH] mv clear node_load[] to __build_all_zonelists()

[Andrew Morton]

On Thu, 6 Aug 2009 19:50:37 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> On Thu, 6 Aug 2009 18:44:40 +0800
> Bo Liu <bo-liu@hotmail.com> wrote:
> 
> > 
> >  If node_load[] is cleared everytime build_zonelists() is called,node_load[]
> >  will have no help to find the next node that should appear in the given node's
> >  fallback list.
> >  Signed-off-by: Bob Liu 
> 
> nice catch. (my old bug...sorry
> 
> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> 
> BTW, do you have special reasons to hide your mail address in commit log ?
> 
> I added proper CC: list.
> Hmm, I think it's necessary to do total review/rewrite this function again..
> 
> 
> > ---
> >  mm/page_alloc.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >  
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index d052abb..72f7345 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -2544,7 +2544,6 @@ static void build_zonelists(pg_data_t *pgdat)
> >  	prev_node = local_node;
> >  	nodes_clear(used_mask);
> >  
> > -	memset(node_load, 0, sizeof(node_load));
> >  	memset(node_order, 0, sizeof(node_order));
> >  	j = 0;
> >  
> > @@ -2653,6 +2652,7 @@ static int __build_all_zonelists(void *dummy)
> >  {
> >  	int nid;
> >  
> > +	memset(node_load, 0, sizeof(node_load));
> >  	for_each_online_node(nid) {
> >  		pg_data_t *pgdat = NODE_DATA(nid);

What are the consequences of this bug?

Is the fix needed in 2.6.31?  Earlier?

Thanks.

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Re: [PATCH] mv clear node_load[] to __build_all_zonelists()

[KAMEZAWA Hiroyuki]

On Mon, 17 Aug 2009 14:34:47 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> On Thu, 6 Aug 2009 19:50:37 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> 
> > On Thu, 6 Aug 2009 18:44:40 +0800
> > Bo Liu <bo-liu@hotmail.com> wrote:
> > 
> > > 
> > >  If node_load[] is cleared everytime build_zonelists() is called,node_load[]
> > >  will have no help to find the next node that should appear in the given node's
> > >  fallback list.
> > >  Signed-off-by: Bob Liu 
> > 
> > nice catch. (my old bug...sorry
> > 
> > Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> > 
> > BTW, do you have special reasons to hide your mail address in commit log ?
> > 
> > I added proper CC: list.
> > Hmm, I think it's necessary to do total review/rewrite this function again..
> > 
> > 
> > > ---
> > >  mm/page_alloc.c |    2 +-
> > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > >  
> > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > > index d052abb..72f7345 100644
> > > --- a/mm/page_alloc.c
> > > +++ b/mm/page_alloc.c
> > > @@ -2544,7 +2544,6 @@ static void build_zonelists(pg_data_t *pgdat)
> > >  	prev_node = local_node;
> > >  	nodes_clear(used_mask);
> > >  
> > > -	memset(node_load, 0, sizeof(node_load));
> > >  	memset(node_order, 0, sizeof(node_order));
> > >  	j = 0;
> > >  
> > > @@ -2653,6 +2652,7 @@ static int __build_all_zonelists(void *dummy)
> > >  {
> > >  	int nid;
> > >  
> > > +	memset(node_load, 0, sizeof(node_load));
> > >  	for_each_online_node(nid) {
> > >  		pg_data_t *pgdat = NODE_DATA(nid);
> 
> What are the consequences of this bug?
> 
> Is the fix needed in 2.6.31?  Earlier?
> 
I think this should be on fast-track as bugfix.

By this bug, zonelist's node_order is not calculated as expected.
This bug affects on big machine, which has asynmetric node distance.

[synmetric NUMA's node distance]
     0    1    2
0   10   12   12
1   12   10   12
2   12   12   10

[asynmetric NUMA's node distance]
     0    1    2
0   10   12   20
1   12   10   14
2   20   14   10


This (my bug) is very old..but no one have reported this for a long time.
Maybe because the number of asynmetric NUMA is very small and they use cpuset
for customizing node memory allocation fallback.

Thanks,
-Kame

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RE: [PATCH] mv clear node_load[] to __build_all_zonelists()

[Bo Liu]

 
On Tue, 18 Aug 2009 09:12:03 +0900
KAMEZAWA Hiroyuki wrote:
>
> On Mon, 17 Aug 2009 14:34:47 -0700
> Andrew Morton wrote:
>
>> On Thu, 6 Aug 2009 19:50:37 +0900
>> KAMEZAWA Hiroyuki wrote:
>>
>>> On Thu, 6 Aug 2009 18:44:40 +0800
>>> Bo Liu wrote:
>>>
>>>>
>>>> If node_load[] is cleared everytime build_zonelists() is called,node_load[]
>>>> will have no help to find the next node that should appear in the given node's
>>>> fallback list.
>>>> Signed-off-by: Bob Liu
>>>
>>> nice catch. (my old bug...sorry
>>>
>>> Reviewed-by: KAMEZAWA Hiroyuki 
>>>
>>> BTW, do you have special reasons to hide your mail address in commit log ?
>>>
>>> I added proper CC: list.
>>> Hmm, I think it's necessary to do total review/rewrite this function again..
>>>
>>>
>>>> ---
>>>> mm/page_alloc.c | 2 +-
>>>> 1 files changed, 1 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>>> index d052abb..72f7345 100644
>>>> --- a/mm/page_alloc.c
>>>> +++ b/mm/page_alloc.c
>>>> @@ -2544,7 +2544,6 @@ static void build_zonelists(pg_data_t *pgdat)
>>>> prev_node = local_node;
>>>> nodes_clear(used_mask);
>>>>
>>>> - memset(node_load, 0, sizeof(node_load));
>>>> memset(node_order, 0, sizeof(node_order));
>>>> j = 0;
>>>>
>>>> @@ -2653,6 +2652,7 @@ static int __build_all_zonelists(void *dummy)
>>>> {
>>>> int nid;
>>>>
>>>> + memset(node_load, 0, sizeof(node_load));
>>>> for_each_online_node(nid) {
>>>> pg_data_t *pgdat = NODE_DATA(nid);
>>
>> What are the consequences of this bug?
>>
>> Is the fix needed in 2.6.31? Earlier?
>>
> I think this should be on fast-track as bugfix.
>
> By this bug, zonelist's node_order is not calculated as expected.
> This bug affects on big machine, which has asynmetric node distance.
>
> [synmetric NUMA's node distance]
> 0 1 2
> 0 10 12 12
> 1 12 10 12
> 2 12 12 10
>
> [asynmetric NUMA's node distance]
> 0 1 2
> 0 10 12 20
> 1 12 10 14
> 2 20 14 10
>
 
Thanks for your explanations.
Actually,
When I submited this patch I didn't think so clearly about the consequences.
I just knew the node_load[] will be nouse because of the memset() clear it every time.

>
> This (my bug) is very old..but no one have reported this for a long time.
> Maybe because the number of asynmetric NUMA is very small and they use cpuset
> for customizing node memory allocation fallback.
 
 
 
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