[PATCH] mm: correct the comment when reclaimed pages exceed the scanned pages

[PATCH] mm: correct the comment when reclaimed pages exceed the scanned pages

[zhongjiang]

The commit e1587a494540 ("mm: vmpressure: fix sending wrong events on
underflow") declare that reclaimed pages exceed the scanned pages due
to the thp reclaim. it is incorrect because THP will be spilt to normal
page and loop again. which will result in the scanned pages increment.

Signed-off-by: zhongjiang <zhongjiang@huawei.com>
---
 mm/vmpressure.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index 6063581..0e91ba3 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -116,8 +116,9 @@ static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
 
 	/*
 	 * reclaimed can be greater than scanned in cases
-	 * like THP, where the scanned is 1 and reclaimed
-	 * could be 512
+	 * like reclaimed slab pages, shrink_node just add
+	 * reclaimed page without a related increment to
+	 * scanned pages.
 	 */
 	if (reclaimed >= scanned)
 		goto out;
-- 
1.7.12.4

Re: [PATCH] mm: correct the comment when reclaimed pages exceed the scanned pages

[zhong jiang]

On 2017/6/7 16:31, zhongjiang wrote:
> The commit e1587a494540 ("mm: vmpressure: fix sending wrong events on
> underflow") declare that reclaimed pages exceed the scanned pages due
> to the thp reclaim. it is incorrect because THP will be spilt to normal
> page and loop again. which will result in the scanned pages increment.
>
> Signed-off-by: zhongjiang <zhongjiang@huawei.com>
> ---
>  mm/vmpressure.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/vmpressure.c b/mm/vmpressure.c
> index 6063581..0e91ba3 100644
> --- a/mm/vmpressure.c
> +++ b/mm/vmpressure.c
> @@ -116,8 +116,9 @@ static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
>  
>  	/*
>  	 * reclaimed can be greater than scanned in cases
> -	 * like THP, where the scanned is 1 and reclaimed
> -	 * could be 512
> +	 * like reclaimed slab pages, shrink_node just add
> +	 * reclaimed page without a related increment to
> +	 * scanned pages.
>  	 */
>  	if (reclaimed >= scanned)
>  		goto out;
Hi, minchan

what  suggstion about  the patch

Thanks
zhongjiang

Re: [PATCH] mm: correct the comment when reclaimed pages exceed the scanned pages

[Minchan Kim]

On Wed, Jun 07, 2017 at 04:31:06PM +0800, zhongjiang wrote:
> The commit e1587a494540 ("mm: vmpressure: fix sending wrong events on
> underflow") declare that reclaimed pages exceed the scanned pages due
> to the thp reclaim. it is incorrect because THP will be spilt to normal
> page and loop again. which will result in the scanned pages increment.
> 
> Signed-off-by: zhongjiang <zhongjiang@huawei.com>
> ---
>  mm/vmpressure.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/vmpressure.c b/mm/vmpressure.c
> index 6063581..0e91ba3 100644
> --- a/mm/vmpressure.c
> +++ b/mm/vmpressure.c
> @@ -116,8 +116,9 @@ static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
>  
>  	/*
>  	 * reclaimed can be greater than scanned in cases
> -	 * like THP, where the scanned is 1 and reclaimed
> -	 * could be 512
> +	 * like reclaimed slab pages, shrink_node just add
> +	 * reclaimed page without a related increment to
> +	 * scanned pages.
>  	 */
>  	if (reclaimed >= scanned)
>  		goto out;

Thanks for the fixing my fault!

Acked-by: Minchan Kim <minchan@kernel.org>

Frankly speaking, I'm not sure we need such comment in there at the cost
of maintainance because it would be fragile but easy to fix by above simple
condition so I think it would be better to remove that comment but others
might be different. So, don't have any objection.

Re: [PATCH] mm: correct the comment when reclaimed pages exceed the scanned pages

[zhong jiang]

On 2017/6/8 14:46, Minchan Kim wrote:
> On Wed, Jun 07, 2017 at 04:31:06PM +0800, zhongjiang wrote:
>> The commit e1587a494540 ("mm: vmpressure: fix sending wrong events on
>> underflow") declare that reclaimed pages exceed the scanned pages due
>> to the thp reclaim. it is incorrect because THP will be spilt to normal
>> page and loop again. which will result in the scanned pages increment.
>>
>> Signed-off-by: zhongjiang <zhongjiang@huawei.com>
>> ---
>>  mm/vmpressure.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/vmpressure.c b/mm/vmpressure.c
>> index 6063581..0e91ba3 100644
>> --- a/mm/vmpressure.c
>> +++ b/mm/vmpressure.c
>> @@ -116,8 +116,9 @@ static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
>>  
>>  	/*
>>  	 * reclaimed can be greater than scanned in cases
>> -	 * like THP, where the scanned is 1 and reclaimed
>> -	 * could be 512
>> +	 * like reclaimed slab pages, shrink_node just add
>> +	 * reclaimed page without a related increment to
>> +	 * scanned pages.
>>  	 */
>>  	if (reclaimed >= scanned)
>>  		goto out;
> Thanks for the fixing my fault!
>
> Acked-by: Minchan Kim <minchan@kernel.org>
>
> Frankly speaking, I'm not sure we need such comment in there at the cost
> of maintainance because it would be fragile but easy to fix by above simple
> condition so I think it would be better to remove that comment but others
> might be different. So, don't have any objection.
>
>
> .
>
 Thanks

 Regards
 zhongjiang