[PATCH] Revert "mm: vmpressure: fix sending wrong events on underflow"

[PATCH] Revert "mm: vmpressure: fix sending wrong events on underflow"

[zhongjiang]

This reverts commit e1587a4945408faa58d0485002c110eb2454740c.

THP lru page is reclaimed , THP is split to normal page and loop again.
reclaimed pages should not be bigger than nr_scan.  because of each
loop will increase nr_scan counter.

Signed-off-by: zhongjiang <zhongjiang@huawei.com>
---
 mm/vmpressure.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index 6063581..149fdf6 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -112,16 +112,9 @@ static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
 						    unsigned long reclaimed)
 {
 	unsigned long scale = scanned + reclaimed;
-	unsigned long pressure = 0;
+	unsigned long pressure;
 
 	/*
-	 * reclaimed can be greater than scanned in cases
-	 * like THP, where the scanned is 1 and reclaimed
-	 * could be 512
-	 */
-	if (reclaimed >= scanned)
-		goto out;
-	/*
 	 * We calculate the ratio (in percents) of how many pages were
 	 * scanned vs. reclaimed in a given time frame (window). Note that
 	 * time is in VM reclaimer's "ticks", i.e. number of pages
@@ -131,7 +124,6 @@ static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
 	pressure = scale - (reclaimed * scale / scanned);
 	pressure = pressure * 100 / scale;
 
-out:
 	pr_debug("%s: %3lu  (s: %lu  r: %lu)\n", __func__, pressure,
 		 scanned, reclaimed);
 
-- 
1.7.12.4

Re: [PATCH] Revert "mm: vmpressure: fix sending wrong events on underflow"

[Minchan Kim]

On Wed, Jun 07, 2017 at 11:08:37AM +0800, zhongjiang wrote:
> This reverts commit e1587a4945408faa58d0485002c110eb2454740c.
> 
> THP lru page is reclaimed , THP is split to normal page and loop again.
> reclaimed pages should not be bigger than nr_scan.  because of each
> loop will increase nr_scan counter.

Unfortunately, there is still underflow issue caused by slab pages as
Vinayak reported in description of e1587a4945408 so we cannot revert.
Please correct comment instead of removing the logic.

Thanks.

> 
> Signed-off-by: zhongjiang <zhongjiang@huawei.com>
> ---
>  mm/vmpressure.c | 10 +---------
>  1 file changed, 1 insertion(+), 9 deletions(-)
> 
> diff --git a/mm/vmpressure.c b/mm/vmpressure.c
> index 6063581..149fdf6 100644
> --- a/mm/vmpressure.c
> +++ b/mm/vmpressure.c
> @@ -112,16 +112,9 @@ static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
>  						    unsigned long reclaimed)
>  {
>  	unsigned long scale = scanned + reclaimed;
> -	unsigned long pressure = 0;
> +	unsigned long pressure;
>  
>  	/*
> -	 * reclaimed can be greater than scanned in cases
> -	 * like THP, where the scanned is 1 and reclaimed
> -	 * could be 512
> -	 */
> -	if (reclaimed >= scanned)
> -		goto out;
> -	/*
>  	 * We calculate the ratio (in percents) of how many pages were
>  	 * scanned vs. reclaimed in a given time frame (window). Note that
>  	 * time is in VM reclaimer's "ticks", i.e. number of pages
> @@ -131,7 +124,6 @@ static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
>  	pressure = scale - (reclaimed * scale / scanned);
>  	pressure = pressure * 100 / scale;
>  
> -out:
>  	pr_debug("%s: %3lu  (s: %lu  r: %lu)\n", __func__, pressure,
>  		 scanned, reclaimed);
>  
> -- 
> 1.7.12.4
> 

Re: [PATCH] Revert "mm: vmpressure: fix sending wrong events on underflow"

[zhong jiang]

On 2017/6/7 11:55, Minchan Kim wrote:
> On Wed, Jun 07, 2017 at 11:08:37AM +0800, zhongjiang wrote:
>> This reverts commit e1587a4945408faa58d0485002c110eb2454740c.
>>
>> THP lru page is reclaimed , THP is split to normal page and loop again.
>> reclaimed pages should not be bigger than nr_scan.  because of each
>> loop will increase nr_scan counter.
> Unfortunately, there is still underflow issue caused by slab pages as
> Vinayak reported in description of e1587a4945408 so we cannot revert.
> Please correct comment instead of removing the logic.
>
> Thanks.
  we calculate the vmpressue based on the Lru page, exclude the slab pages by previous
  discussion.    is it not this?

  Thanks
 zhongjiang
>> Signed-off-by: zhongjiang <zhongjiang@huawei.com>
>> ---
>>  mm/vmpressure.c | 10 +---------
>>  1 file changed, 1 insertion(+), 9 deletions(-)
>>
>> diff --git a/mm/vmpressure.c b/mm/vmpressure.c
>> index 6063581..149fdf6 100644
>> --- a/mm/vmpressure.c
>> +++ b/mm/vmpressure.c
>> @@ -112,16 +112,9 @@ static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
>>  						    unsigned long reclaimed)
>>  {
>>  	unsigned long scale = scanned + reclaimed;
>> -	unsigned long pressure = 0;
>> +	unsigned long pressure;
>>  
>>  	/*
>> -	 * reclaimed can be greater than scanned in cases
>> -	 * like THP, where the scanned is 1 and reclaimed
>> -	 * could be 512
>> -	 */
>> -	if (reclaimed >= scanned)
>> -		goto out;
>> -	/*
>>  	 * We calculate the ratio (in percents) of how many pages were
>>  	 * scanned vs. reclaimed in a given time frame (window). Note that
>>  	 * time is in VM reclaimer's "ticks", i.e. number of pages
>> @@ -131,7 +124,6 @@ static enum vmpressure_levels vmpressure_calc_level(unsigned long scanned,
>>  	pressure = scale - (reclaimed * scale / scanned);
>>  	pressure = pressure * 100 / scale;
>>  
>> -out:
>>  	pr_debug("%s: %3lu  (s: %lu  r: %lu)\n", __func__, pressure,
>>  		 scanned, reclaimed);
>>  
>> -- 
>> 1.7.12.4
>>
> .
>

Re: [PATCH] Revert "mm: vmpressure: fix sending wrong events on underflow"

[Minchan Kim]

On Wed, Jun 07, 2017 at 12:56:57PM +0800, zhong jiang wrote:
> On 2017/6/7 11:55, Minchan Kim wrote:
> > On Wed, Jun 07, 2017 at 11:08:37AM +0800, zhongjiang wrote:
> >> This reverts commit e1587a4945408faa58d0485002c110eb2454740c.
> >>
> >> THP lru page is reclaimed , THP is split to normal page and loop again.
> >> reclaimed pages should not be bigger than nr_scan.  because of each
> >> loop will increase nr_scan counter.
> > Unfortunately, there is still underflow issue caused by slab pages as
> > Vinayak reported in description of e1587a4945408 so we cannot revert.
> > Please correct comment instead of removing the logic.
> >
> > Thanks.
>   we calculate the vmpressue based on the Lru page, exclude the slab pages by previous
>   discussion.    is it not this?
> 

IIRC, It is not merged into mainline although mmotm has it.

Re: [PATCH] Revert "mm: vmpressure: fix sending wrong events on underflow"

[vinayak menon]

On Wed, Jun 7, 2017 at 11:42 AM, Minchan Kim <minchan@kernel.org> wrote:
> On Wed, Jun 07, 2017 at 12:56:57PM +0800, zhong jiang wrote:
>> On 2017/6/7 11:55, Minchan Kim wrote:
>> > On Wed, Jun 07, 2017 at 11:08:37AM +0800, zhongjiang wrote:
>> >> This reverts commit e1587a4945408faa58d0485002c110eb2454740c.
>> >>
>> >> THP lru page is reclaimed , THP is split to normal page and loop again.
>> >> reclaimed pages should not be bigger than nr_scan.  because of each
>> >> loop will increase nr_scan counter.
>> > Unfortunately, there is still underflow issue caused by slab pages as
>> > Vinayak reported in description of e1587a4945408 so we cannot revert.
>> > Please correct comment instead of removing the logic.
>> >
>> > Thanks.
>>   we calculate the vmpressue based on the Lru page, exclude the slab pages by previous
>>   discussion.    is it not this?
>>
>
> IIRC, It is not merged into mainline although mmotm has it.

That's right Minchan. That patch was not mainlined.

Re: [PATCH] Revert "mm: vmpressure: fix sending wrong events on underflow"

[zhong jiang]

On 2017/6/7 14:17, vinayak menon wrote:
> On Wed, Jun 7, 2017 at 11:42 AM, Minchan Kim <minchan@kernel.org> wrote:
>> On Wed, Jun 07, 2017 at 12:56:57PM +0800, zhong jiang wrote:
>>> On 2017/6/7 11:55, Minchan Kim wrote:
>>>> On Wed, Jun 07, 2017 at 11:08:37AM +0800, zhongjiang wrote:
>>>>> This reverts commit e1587a4945408faa58d0485002c110eb2454740c.
>>>>>
>>>>> THP lru page is reclaimed , THP is split to normal page and loop again.
>>>>> reclaimed pages should not be bigger than nr_scan.  because of each
>>>>> loop will increase nr_scan counter.
>>>> Unfortunately, there is still underflow issue caused by slab pages as
>>>> Vinayak reported in description of e1587a4945408 so we cannot revert.
>>>> Please correct comment instead of removing the logic.
>>>>
>>>> Thanks.
>>>   we calculate the vmpressue based on the Lru page, exclude the slab pages by previous
>>>   discussion.    is it not this?
>>>
>> IIRC, It is not merged into mainline although mmotm has it.
> That's right Minchan. That patch was not mainlined.
>
>
 Hi  Minchan and vinayak

 we should revert the patch (mm: vmpressure: fix sending wrong events on underflow), then
 apply the mmotm's related patch. or drop the mmotm's related patch, then corrent the comment.

 which one make more sense.  Maybe the latter is more feasible. Suggestion ?

 Thanks
 zhongjiang