[PATCH] mm: update the description for vm_total_pages

[PATCH] mm: update the description for vm_total_pages

[Wang Sheng-Hui]

vm_total_pages is calculated by nr_free_pagecache_pages(), which counts
the number of pages which are beyond the high watermark within all zones.
So vm_total_pages is not equal to total number of pages which the VM controls.

Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
---
 mm/vmscan.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 0f16ffe..8c7a559 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -136,7 +136,11 @@ struct scan_control {
  * From 0 .. 100.  Higher means more swappy.
  */
 int vm_swappiness = 60;
-unsigned long vm_total_pages;  /* The total number of pages which the VM controls */
+/*
+ * The total number of pages which are beyond the high watermark
+ * within all zones.
+ */
+unsigned long vm_total_pages;

 static LIST_HEAD(shrinker_list);
 static DECLARE_RWSEM(shrinker_rwsem);
-- 
1.8.3.2

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Re: [PATCH] mm: update the description for vm_total_pages

[Andrew Morton]

On Tue, 08 Jul 2014 13:44:51 +0800 Wang Sheng-Hui <shhuiw@gmail.com> wrote:

> 
> vm_total_pages is calculated by nr_free_pagecache_pages(), which counts
> the number of pages which are beyond the high watermark within all zones.
> So vm_total_pages is not equal to total number of pages which the VM controls.
> 
> ...
>
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -136,7 +136,11 @@ struct scan_control {
>   * From 0 .. 100.  Higher means more swappy.
>   */
>  int vm_swappiness = 60;
> -unsigned long vm_total_pages;  /* The total number of pages which the VM controls */
> +/*
> + * The total number of pages which are beyond the high watermark
> + * within all zones.
> + */
> +unsigned long vm_total_pages;
> 
>  static LIST_HEAD(shrinker_list);
>  static DECLARE_RWSEM(shrinker_rwsem);

Nice patch!  It's good to document these little things as one discovers
them.

However vm_total_pages is only ever used in build_all_zonelists() and
could be made a local within that function.

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Re: [PATCH] mm: update the description for vm_total_pages

[Wang Sheng-Hui]

Andrew,

On 2014a1'07ae??09ae?JPY 04:41, Andrew Morton wrote:
> On Tue, 08 Jul 2014 13:44:51 +0800 Wang Sheng-Hui <shhuiw@gmail.com> wrote:
> 
>>
>> vm_total_pages is calculated by nr_free_pagecache_pages(), which counts
>> the number of pages which are beyond the high watermark within all zones.
>> So vm_total_pages is not equal to total number of pages which the VM controls.
>>
>> ...
>>
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -136,7 +136,11 @@ struct scan_control {
>>   * From 0 .. 100.  Higher means more swappy.
>>   */
>>  int vm_swappiness = 60;
>> -unsigned long vm_total_pages;  /* The total number of pages which the VM controls */
>> +/*
>> + * The total number of pages which are beyond the high watermark
>> + * within all zones.
>> + */
>> +unsigned long vm_total_pages;
>>
>>  static LIST_HEAD(shrinker_list);
>>  static DECLARE_RWSEM(shrinker_rwsem);
> 
> Nice patch!  It's good to document these little things as one discovers
> them.
> 
> However vm_total_pages is only ever used in build_all_zonelists() and
> could be made a local within that function.

We can see that vm_total_pages is not used in build_all_zonelist() only.
          http://lxr.oss.org.cn/search?string=vm_total_pages

Maybe some redefinition is needed instead of current definition in vmscan.c.:-)

>

Regards,
Wang Sheng-Hui

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Re: [PATCH] mm: update the description for vm_total_pages

[Andrew Morton]

On Wed, 09 Jul 2014 07:45:06 +0800 Wang Sheng-Hui <shhuiw@gmail.com> wrote:

> >> +unsigned long vm_total_pages;
> >>
> >>  static LIST_HEAD(shrinker_list);
> >>  static DECLARE_RWSEM(shrinker_rwsem);
> > 
> > Nice patch!  It's good to document these little things as one discovers
> > them.
> > 
> > However vm_total_pages is only ever used in build_all_zonelists() and
> > could be made a local within that function.
> 
> We can see that vm_total_pages is not used in build_all_zonelist() only.
>           http://lxr.oss.org.cn/search?string=vm_total_pages

Look more closely ;)

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