[v2] watermark related improvement on zone movable

[PATCH v2 1/2] mm: Cap zone movable's min wmark to small value

Posted by Wupeng Ma 3 years, 7 months ago

From: Ma Wupeng <mawupeng1@huawei.com>

Since min_free_kbytes is based on gfp_zone(GFP_USER) which does not include
zone movable. However zone movable will get its min share in
__setup_per_zone_wmarks() which does not make any sense.

And like highmem pages, __GFP_HIGH and PF_MEMALLOC allocations usually
don't need movable pages, so there is no need to assign min pages for zone
movable.

Let's cap pages_min for zone movable to a small value here just link
highmem pages.

Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
---
 mm/page_alloc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e5486d47406e..ff644205370f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8638,7 +8638,7 @@ static void __setup_per_zone_wmarks(void)
 
 	/* Calculate total number of !ZONE_HIGHMEM pages */
 	for_each_zone(zone) {
-		if (!is_highmem(zone))
+		if (!is_highmem(zone) && zone_idx(zone) != ZONE_MOVABLE)
 			lowmem_pages += zone_managed_pages(zone);
 	}
 
@@ -8648,7 +8648,7 @@ static void __setup_per_zone_wmarks(void)
 		spin_lock_irqsave(&zone->lock, flags);
 		tmp = (u64)pages_min * zone_managed_pages(zone);
 		do_div(tmp, lowmem_pages);
-		if (is_highmem(zone)) {
+		if (is_highmem(zone) || zone_idx(zone) == ZONE_MOVABLE) {
 			/*
 			 * __GFP_HIGH and PF_MEMALLOC allocations usually don't
 			 * need highmem pages, so cap pages_min to a small
-- 
2.25.1

Re: [PATCH v2 1/2] mm: Cap zone movable's min wmark to small value

Posted by David Hildenbrand 3 years, 7 months ago

On 19.08.22 11:30, Wupeng Ma wrote:
> From: Ma Wupeng <mawupeng1@huawei.com>
> 
> Since min_free_kbytes is based on gfp_zone(GFP_USER) which does not include
> zone movable. However zone movable will get its min share in
> __setup_per_zone_wmarks() which does not make any sense.
> 
> And like highmem pages, __GFP_HIGH and PF_MEMALLOC allocations usually
> don't need movable pages, so there is no need to assign min pages for zone
> movable.
> 
> Let's cap pages_min for zone movable to a small value here just link
> highmem pages.
> 
> Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
> ---
>  mm/page_alloc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e5486d47406e..ff644205370f 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8638,7 +8638,7 @@ static void __setup_per_zone_wmarks(void)
>  
>  	/* Calculate total number of !ZONE_HIGHMEM pages */
>  	for_each_zone(zone) {
> -		if (!is_highmem(zone))
> +		if (!is_highmem(zone) && zone_idx(zone) != ZONE_MOVABLE)
>  			lowmem_pages += zone_managed_pages(zone);
>  	}
>  
> @@ -8648,7 +8648,7 @@ static void __setup_per_zone_wmarks(void)
>  		spin_lock_irqsave(&zone->lock, flags);
>  		tmp = (u64)pages_min * zone_managed_pages(zone);
>  		do_div(tmp, lowmem_pages);
> -		if (is_highmem(zone)) {
> +		if (is_highmem(zone) || zone_idx(zone) == ZONE_MOVABLE) {
>  			/*
>  			 * __GFP_HIGH and PF_MEMALLOC allocations usually don't
>  			 * need highmem pages, so cap pages_min to a small

This kind-off makes sense to me, but I'm not completely sure about all
implications. We most certainly should update the comment as well.

-- 
Thanks,

David / dhildenb

Re: [PATCH v2 1/2] mm: Cap zone movable's min wmark to small value

Posted by mawupeng 3 years, 7 months ago


On 2022/8/24 16:10, David Hildenbrand wrote:
> On 19.08.22 11:30, Wupeng Ma wrote:
>> From: Ma Wupeng <mawupeng1@huawei.com>
>>
>> Since min_free_kbytes is based on gfp_zone(GFP_USER) which does not include
>> zone movable. However zone movable will get its min share in
>> __setup_per_zone_wmarks() which does not make any sense.
>>
>> And like highmem pages, __GFP_HIGH and PF_MEMALLOC allocations usually
>> don't need movable pages, so there is no need to assign min pages for zone
>> movable.
>>
>> Let's cap pages_min for zone movable to a small value here just link
>> highmem pages.
>>
>> Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>
>> ---
>>  mm/page_alloc.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index e5486d47406e..ff644205370f 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -8638,7 +8638,7 @@ static void __setup_per_zone_wmarks(void)
>>  
>>  	/* Calculate total number of !ZONE_HIGHMEM pages */
>>  	for_each_zone(zone) {
>> -		if (!is_highmem(zone))
>> +		if (!is_highmem(zone) && zone_idx(zone) != ZONE_MOVABLE)
>>  			lowmem_pages += zone_managed_pages(zone);
>>  	}
>>  
>> @@ -8648,7 +8648,7 @@ static void __setup_per_zone_wmarks(void)
>>  		spin_lock_irqsave(&zone->lock, flags);
>>  		tmp = (u64)pages_min * zone_managed_pages(zone);
>>  		do_div(tmp, lowmem_pages);
>> -		if (is_highmem(zone)) {
>> +		if (is_highmem(zone) || zone_idx(zone) == ZONE_MOVABLE) {
>>  			/*
>>  			 * __GFP_HIGH and PF_MEMALLOC allocations usually don't
>>  			 * need highmem pages, so cap pages_min to a small
> 
> This kind-off makes sense to me, but I'm not completely sure about all
> implications. We most certainly should update the comment as well.

Yes, we should certainly do this.

Thanks for reviewing.

>