linux-kernel - Re: [PATCH next] mm/swap.c: reduce lock contention in lru_cache

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Date:   Thu, 26 Nov 2020 14:39:03 +0800
From:   Alex Shi <alex.shi@...ux.alibaba.com>
To:     Yu Zhao <yuzhao@...gle.com>
Cc:     Konstantin Khlebnikov <koct9i@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hugh Dickins <hughd@...gle.com>,
        Michal Hocko <mhocko@...e.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH next] mm/swap.c: reduce lock contention in lru_cache_add



在 2020/11/26 下午12:52, Yu Zhao 写道:
>>   */
>>  void __pagevec_lru_add(struct pagevec *pvec)
>>  {
>> -	int i;
>> -	struct lruvec *lruvec = NULL;
>> +	int i, nr_lruvec;
>>  	unsigned long flags = 0;
>> +	struct page *page;
>> +	struct lruvecs lruvecs;
>>  
>> -	for (i = 0; i < pagevec_count(pvec); i++) {
>> -		struct page *page = pvec->pages[i];
>> +	nr_lruvec = sort_page_lruvec(&lruvecs, pvec);
> Simply looping pvec multiple times (15 at most) for different lruvecs
> would be better because 1) it requires no extra data structures and
> therefore has better cache locality (theoretically faster) 2) it only
> loops once when !CONFIG_MEMCG and !CONFIG_NUMA and therefore has no
> impact on Android and Chrome OS.
> 

With multiple memcgs, it do help a lot, I had gotten 30% grain on readtwice
case. but yes, w/o MEMCG and NUMA, it's good to keep old behavior. So 
would you like has a proposal for this?

Thanks
Alex