Add Ying who found out the large folio is not batched added to lru.
On 4/18/23 09:57, Yin Fengwei wrote:
>
>
> On 4/17/23 20:25, Matthew Wilcox wrote:
>> On Mon, Apr 17, 2023 at 03:56:43PM +0800, Yin Fengwei wrote:
>>> Currently, large folio is not batched added to lru list. Which
>>> cause high lru lock contention after enable large folio for
>>> anonymous mappping.
>>
>> Obviously, I think we should be doing a batched add, but I don't think
>> this is right.
>>
>>> @@ -54,7 +57,12 @@ static inline unsigned pagevec_space(struct pagevec *pvec)
>>> static inline unsigned pagevec_add(struct pagevec *pvec, struct page *page)
>>> {
>>> pvec->pages[pvec->nr++] = page;
>>> - return pagevec_space(pvec);
>>> + pvec->pages_nr += compound_nr(page);
>>> +
>>> + if (pvec->pages_nr > PAGEVEC_SIZE)
>>> + return 0;
>>> + else
>>> + return pagevec_space(pvec);
>>
>> I assume your thinking here is that we should limit the number of pages
>> in the batches, but I think we should allow the number of folios to reach
>> PAGEVEC_SIZE before we drain the batch onto the LRU list. That will
>> reduce the contention on the LRU lock even further.
>
> Yes. The first thought in my mind was to limit the number of folios also.
>
> But the concern is that large folio has wider range of size. In the extreme
> case, if all batched large folios has 2M size, with PAGEVEC_SIZE as 15,
> one batch could have 30M memory. Which could be too large for some usages.
>
>
> Regards
> Yin, Fengwei
>
>>
