[mmotm] mm/page_owner: align with pageblock_nr_pages

[mmotm] mm/page_owner: align with pageblock_nr_pages

[zhong jiang]

Currently, init_pages_in_zone walk the zone in pageblock_nr_pages
steps.  MAX_ORDER_NR_PAGES is possible to have holes when
CONFIG_HOLES_IN_ZONE is set. it is likely to be different between
MAX_ORDER_NR_PAGES and pageblock_nr_pages. if we skip the size of
MAX_ORDER_NR_PAGES, it will result in the second 2M memroy leak.

meanwhile, the change will make the code consistent. because the
entire function is based on the pageblock_nr_pages steps.

Signed-off-by: zhong jiang <zhongjiang@huawei.com>
---
 mm/page_owner.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index 60634dc..754efdd 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -527,7 +527,7 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
 	 */
 	for (; pfn < end_pfn; ) {
 		if (!pfn_valid(pfn)) {
-			pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
+			pfn = ALIGN(pfn + 1, pageblock_nr_pages);
 			continue;
 		}
 
-- 
1.8.3.1

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Re: [mmotm] mm/page_owner: align with pageblock_nr_pages

[Andrew Morton]

On Mon, 4 Dec 2017 21:48:04 +0800 zhong jiang <zhongjiang@huawei.com> wrote:

> Currently, init_pages_in_zone walk the zone in pageblock_nr_pages
> steps.  MAX_ORDER_NR_PAGES is possible to have holes when
> CONFIG_HOLES_IN_ZONE is set. it is likely to be different between
> MAX_ORDER_NR_PAGES and pageblock_nr_pages. if we skip the size of
> MAX_ORDER_NR_PAGES, it will result in the second 2M memroy leak.
> 
> meanwhile, the change will make the code consistent. because the
> entire function is based on the pageblock_nr_pages steps.
> 
> ...
>
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -527,7 +527,7 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
>  	 */
>  	for (; pfn < end_pfn; ) {
>  		if (!pfn_valid(pfn)) {
> -			pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
> +			pfn = ALIGN(pfn + 1, pageblock_nr_pages);
>  			continue;
>  		}

I *think* Michal and Vlastimil will be OK with this as-newly-presented.
Guys, can you please have another think?

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Re: [mmotm] mm/page_owner: align with pageblock_nr_pages

[zhong jiang]

On 2017/12/6 8:58, Andrew Morton wrote:
> On Mon, 4 Dec 2017 21:48:04 +0800 zhong jiang <zhongjiang@huawei.com> wrote:
>
>> Currently, init_pages_in_zone walk the zone in pageblock_nr_pages
>> steps.  MAX_ORDER_NR_PAGES is possible to have holes when
>> CONFIG_HOLES_IN_ZONE is set. it is likely to be different between
>> MAX_ORDER_NR_PAGES and pageblock_nr_pages. if we skip the size of
>> MAX_ORDER_NR_PAGES, it will result in the second 2M memroy leak.
>>
>> meanwhile, the change will make the code consistent. because the
>> entire function is based on the pageblock_nr_pages steps.
>>
>> ...
>>
>> --- a/mm/page_owner.c
>> +++ b/mm/page_owner.c
>> @@ -527,7 +527,7 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
>>  	 */
>>  	for (; pfn < end_pfn; ) {
>>  		if (!pfn_valid(pfn)) {
>> -			pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
>> +			pfn = ALIGN(pfn + 1, pageblock_nr_pages);
>>  			continue;
>>  		}
> I *think* Michal and Vlastimil will be OK with this as-newly-presented.
> Guys, can you please have another think?
According to Vlastimil's comment,  it is not simple as it looks to cover all corners.
Maybe  architecture need explicit define the hole granularity to use correctly.
so far,  I have no a good idea to solve it perfectly. 
Anyway. I will go further to find out.

Thanks
zhong jiang


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Re: [mmotm] mm/page_owner: align with pageblock_nr_pages

[Michal Hocko]

On Wed 06-12-17 10:44:23, zhong jiang wrote:
> On 2017/12/6 8:58, Andrew Morton wrote:
> > On Mon, 4 Dec 2017 21:48:04 +0800 zhong jiang <zhongjiang@huawei.com> wrote:
> >
> >> Currently, init_pages_in_zone walk the zone in pageblock_nr_pages
> >> steps.  MAX_ORDER_NR_PAGES is possible to have holes when
> >> CONFIG_HOLES_IN_ZONE is set. it is likely to be different between
> >> MAX_ORDER_NR_PAGES and pageblock_nr_pages. if we skip the size of
> >> MAX_ORDER_NR_PAGES, it will result in the second 2M memroy leak.
> >>
> >> meanwhile, the change will make the code consistent. because the
> >> entire function is based on the pageblock_nr_pages steps.
> >>
> >> ...
> >>
> >> --- a/mm/page_owner.c
> >> +++ b/mm/page_owner.c
> >> @@ -527,7 +527,7 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
> >>  	 */
> >>  	for (; pfn < end_pfn; ) {
> >>  		if (!pfn_valid(pfn)) {
> >> -			pfn = ALIGN(pfn + 1, MAX_ORDER_NR_PAGES);
> >> +			pfn = ALIGN(pfn + 1, pageblock_nr_pages);
> >>  			continue;
> >>  		}
> > I *think* Michal and Vlastimil will be OK with this as-newly-presented.
> > Guys, can you please have another think?
> According to Vlastimil's comment,  it is not simple as it looks to cover all corners.
> Maybe  architecture need explicit define the hole granularity to use correctly.
> so far,  I have no a good idea to solve it perfectly. 
> Anyway. I will go further to find out.

Yes please! The thing is clear as mud right now and doing cosmetic
changes without further clarification doesn't help to improve the
situation much.
-- 
Michal Hocko
SUSE Labs

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