Re: [PATCH v6 4/4] mm/hotplug: enable memory hotplug for non-lru movable pages

[Yisheng Xie]

Hi Naoya Horiguchi,
Thanks for reviewing.

On 2017/2/6 11:29, Naoya Horiguchi wrote:
> On Fri, Feb 03, 2017 at 03:59:30PM +0800, Yisheng Xie wrote:
>> We had considered all of the non-lru pages as unmovable before commit
>> bda807d44454 ("mm: migrate: support non-lru movable page migration").  But
>> now some of non-lru pages like zsmalloc, virtio-balloon pages also become
>> movable.  So we can offline such blocks by using non-lru page migration.
>>
>> This patch straightforwardly adds non-lru migration code, which means
>> adding non-lru related code to the functions which scan over pfn and
>> collect pages to be migrated and isolate them before migration.
>>
>> Signed-off-by: Yisheng Xie <xieyisheng1@xxxxxxxxxx>
>> Cc: Michal Hocko <mhocko@xxxxxxxxxx>
>> Cc: Minchan Kim <minchan@xxxxxxxxxx>
>> Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
>> Cc: Vlastimil Babka <vbabka@xxxxxxx>
>> Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
>> Cc: Hanjun Guo <guohanjun@xxxxxxxxxx>
>> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
>> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
>> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
>> Cc: Reza Arbab <arbab@xxxxxxxxxxxxxxxxxx>
>> Cc: Taku Izumi <izumi.taku@xxxxxxxxxxxxxx>
>> Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
>> Cc: Xishi Qiu <qiuxishi@xxxxxxxxxx>
>> ---
>>  mm/memory_hotplug.c | 28 +++++++++++++++++-----------
>>  mm/page_alloc.c     |  8 ++++++--
>>  2 files changed, 23 insertions(+), 13 deletions(-)
>>
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index ca2723d..ea1be08 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1516,10 +1516,10 @@ int test_pages_in_a_zone(unsigned long start_pfn, unsigned long end_pfn)
>>  }
>>  
>>  /*
>> - * Scan pfn range [start,end) to find movable/migratable pages (LRU pages
>> - * and hugepages). We scan pfn because it's much easier than scanning over
>> - * linked list. This function returns the pfn of the first found movable
>> - * page if it's found, otherwise 0.
>> + * Scan pfn range [start,end) to find movable/migratable pages (LRU pages,
>> + * non-lru movable pages and hugepages). We scan pfn because it's much
>> + * easier than scanning over linked list. This function returns the pfn
>> + * of the first found movable page if it's found, otherwise 0.
>>   */
>>  static unsigned long scan_movable_pages(unsigned long start, unsigned long end)
>>  {
>> @@ -1530,6 +1530,8 @@ static unsigned long scan_movable_pages(unsigned long start, unsigned long end)
>>  			page = pfn_to_page(pfn);
>>  			if (PageLRU(page))
>>  				return pfn;
>> +			if (__PageMovable(page))
>> +				return pfn;
>>  			if (PageHuge(page)) {
>>  				if (page_huge_active(page))
>>  					return pfn;
>> @@ -1606,21 +1608,25 @@ static struct page *new_node_page(struct page *page, unsigned long private,
>>  		if (!get_page_unless_zero(page))
>>  			continue;
>>  		/*
>> -		 * We can skip free pages. And we can only deal with pages on
>> -		 * LRU.
>> +		 * We can skip free pages. And we can deal with pages on
>> +		 * LRU and non-lru movable pages.
>>  		 */
>> -		ret = isolate_lru_page(page);
>> +		if (PageLRU(page))
>> +			ret = isolate_lru_page(page);
>> +		else
>> +			ret = isolate_movable_page(page, ISOLATE_UNEVICTABLE);
>>  		if (!ret) { /* Success */
>>  			put_page(page);
>>  			list_add_tail(&page->lru, &source);
>>  			move_pages--;
>> -			inc_node_page_state(page, NR_ISOLATED_ANON +
>> -					    page_is_file_cache(page));
>> +			if (!__PageMovable(page))
> 
> If this check is identical with "if (PageLRU(page))" in this context,
> PageLRU(page) looks better because you already add same "if" above.
> 
After isolated lru page, the PageLRU will be cleared, so use !__PageMovable
instead here for LRU page's mapping cannot have PAGE_MAPPING_MOVABLE.

I have add the comment in PATCH[3/4] HWPOISON: soft offlining for non-lru
movable page, so I do not add the same comment here.

Thanks
Yisheng Xie

> Otherwise, looks good to me.
> 
> Thanks,
> Naoya Horiguchi
> .
>