diff mbox series

[v2] mm/page_alloc: fix counting of free pages after take off from buddy

Message ID 20210508035533.23222-1-dinghui@sangfor.com.cn (mailing list archive)
State New
Headers show
Series [v2] mm/page_alloc: fix counting of free pages after take off from buddy | expand

Commit Message

Ding Hui May 8, 2021, 3:55 a.m. UTC
Recently we found there is a lot MemFree left in /proc/meminfo after
do a lot of pages soft offline.

I think it's incorrect since NR_FREE_PAGES should not contain HWPoison pages.
For offline free pages, after a successful call take_page_off_buddy(), the
page is no longer belong to buddy allocator, and will not be used any more,
but we missed accounting NR_FREE_PAGES in this situation.

Do update like rmqueue() does.

Signed-off-by: Ding Hui <dinghui@sangfor.com.cn>
---
V2:
use __mod_zone_freepage_state instead of __mod_zone_page_state

 mm/page_alloc.c | 1 +
 1 file changed, 1 insertion(+)

Comments

HORIGUCHI NAOYA(堀口 直也) May 25, 2021, 8:32 a.m. UTC | #1
On Sat, May 08, 2021 at 11:55:33AM +0800, Ding Hui wrote:
> Recently we found there is a lot MemFree left in /proc/meminfo after
> do a lot of pages soft offline.
> 
> I think it's incorrect since NR_FREE_PAGES should not contain HWPoison pages.
> For offline free pages, after a successful call take_page_off_buddy(), the
> page is no longer belong to buddy allocator, and will not be used any more,
> but we missed accounting NR_FREE_PAGES in this situation.
> 
> Do update like rmqueue() does.
> 
> Signed-off-by: Ding Hui <dinghui@sangfor.com.cn>
> ---
> V2:
> use __mod_zone_freepage_state instead of __mod_zone_page_state
> 
>  mm/page_alloc.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cfc72873961d..e124a615303b 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8947,6 +8947,7 @@ bool take_page_off_buddy(struct page *page)
>  			del_page_from_free_list(page_head, zone, page_order);
>  			break_down_buddy_pages(zone, page_head, page, 0,
>  						page_order, migratetype);
> +			__mod_zone_freepage_state(zone, -1, migratetype);

Page offline code (see set_migratetype_isolate()) seems to handle
NR_FREE_PAGES counter in its own way, so I think that it's more correct to
call __mod_zone_freepage_state() only when is_migrate_isolate(migratetype))
is false.

Otherwise, the patch looks good to me.

Thanks,
Naoya Horiguchi

>  			ret = true;
>  			break;
>  		}
> -- 
> 2.17.1
>
Ding Hui May 26, 2021, 12:43 a.m. UTC | #2
On 2021/5/25 16:32, HORIGUCHI NAOYA(堀口 直也) wrote:
> On Sat, May 08, 2021 at 11:55:33AM +0800, Ding Hui wrote:
>> Recently we found there is a lot MemFree left in /proc/meminfo after
>> do a lot of pages soft offline.
>>
>> I think it's incorrect since NR_FREE_PAGES should not contain HWPoison pages.
>> For offline free pages, after a successful call take_page_off_buddy(), the
>> page is no longer belong to buddy allocator, and will not be used any more,
>> but we missed accounting NR_FREE_PAGES in this situation.
>>
>> Do update like rmqueue() does.
>>
>> Signed-off-by: Ding Hui <dinghui@sangfor.com.cn>
>> ---
>> V2:
>> use __mod_zone_freepage_state instead of __mod_zone_page_state
>>
>>   mm/page_alloc.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index cfc72873961d..e124a615303b 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -8947,6 +8947,7 @@ bool take_page_off_buddy(struct page *page)
>>   			del_page_from_free_list(page_head, zone, page_order);
>>   			break_down_buddy_pages(zone, page_head, page, 0,
>>   						page_order, migratetype);
>> +			__mod_zone_freepage_state(zone, -1, migratetype);
> 
> Page offline code (see set_migratetype_isolate()) seems to handle
> NR_FREE_PAGES counter in its own way, so I think that it's more correct to
> call __mod_zone_freepage_state() only when is_migrate_isolate(migratetype))
> is false.
> 
> Otherwise, the patch looks good to me.
> 

Thanks for reply and suggestion, I'll send v3 patch later.

>>   			ret = true;
>>   			break;
>>   		}
>> -- 
>> 2.17.1
diff mbox series

Patch

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cfc72873961d..e124a615303b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8947,6 +8947,7 @@  bool take_page_off_buddy(struct page *page)
 			del_page_from_free_list(page_head, zone, page_order);
 			break_down_buddy_pages(zone, page_head, page, 0,
 						page_order, migratetype);
+			__mod_zone_freepage_state(zone, -1, migratetype);
 			ret = true;
 			break;
 		}