From: Vlastimil Babka <vbabka@suse.cz>
To: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>, Yu Zhao <yuzhao@google.com>,
Michal Hocko <mhocko@suse.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH next] mm/swap.c: reduce lock contention in lru_cache_add
Date: Wed, 25 Nov 2020 16:38:18 +0100 [thread overview]
Message-ID: <b92a1a50-b7cd-0b33-de2e-52d74c91925c@suse.cz> (raw)
In-Reply-To: <1605860847-47445-1-git-send-email-alex.shi@linux.alibaba.com>
On 11/20/20 9:27 AM, Alex Shi wrote:
> The current relock logical will change lru_lock when found a new
> lruvec, so if 2 memcgs are reading file or alloc page at same time,
> they could hold the lru_lock alternately, and wait for each other for
> fairness attribute of ticket spin lock.
>
> This patch will sort that all lru_locks and only hold them once in
> above scenario. That could reduce fairness waiting for lock reget.
> Than, vm-scalability/case-lru-file-readtwice could get ~5% performance
> gain on my 2P*20core*HT machine.
Hm, once you sort the pages like this, it's a shame not to splice them
instead of more list_del() + list_add() iterations. update_lru_size()
could be also called once?
> Suggested-by: Konstantin Khlebnikov <koct9i@gmail.com>
> Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
> Cc: Konstantin Khlebnikov <koct9i@gmail.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Yu Zhao <yuzhao@google.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> ---
> mm/swap.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 49 insertions(+), 8 deletions(-)
>
> diff --git a/mm/swap.c b/mm/swap.c
> index 490553f3f9ef..c787b38bf9c0 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -1009,24 +1009,65 @@ static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec)
> trace_mm_lru_insertion(page, lru);
> }
>
> +struct lruvecs {
> + struct list_head lists[PAGEVEC_SIZE];
> + struct lruvec *vecs[PAGEVEC_SIZE];
> +};
> +
> +/* Sort pvec pages on their lruvec */
> +int sort_page_lruvec(struct lruvecs *lruvecs, struct pagevec *pvec)
> +{
> + int i, j, nr_lruvec;
> + struct page *page;
> + struct lruvec *lruvec = NULL;
> +
> + lruvecs->vecs[0] = NULL;
> + for (i = nr_lruvec = 0; i < pagevec_count(pvec); i++) {
> + page = pvec->pages[i];
> + lruvec = mem_cgroup_page_lruvec(page, page_pgdat(page));
> +
> + /* Try to find a same lruvec */
> + for (j = 0; j <= nr_lruvec; j++)
> + if (lruvec == lruvecs->vecs[j])
> + break;
> +
> + /* A new lruvec */
> + if (j > nr_lruvec) {
> + INIT_LIST_HEAD(&lruvecs->lists[nr_lruvec]);
> + lruvecs->vecs[nr_lruvec] = lruvec;
> + j = nr_lruvec++;
> + lruvecs->vecs[nr_lruvec] = 0;
> + }
> +
> + list_add_tail(&page->lru, &lruvecs->lists[j]);
> + }
> +
> + return nr_lruvec;
> +}
> +
> /*
> * Add the passed pages to the LRU, then drop the caller's refcount
> * on them. Reinitialises the caller's pagevec.
> */
> 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);
>
> - lruvec = relock_page_lruvec_irqsave(page, lruvec, &flags);
> - __pagevec_lru_add_fn(page, lruvec);
> + for (i = 0; i < nr_lruvec; i++) {
> + spin_lock_irqsave(&lruvecs.vecs[i]->lru_lock, flags);
> + while (!list_empty(&lruvecs.lists[i])) {
> + page = lru_to_page(&lruvecs.lists[i]);
> + list_del(&page->lru);
> + __pagevec_lru_add_fn(page, lruvecs.vecs[i]);
> + }
> + spin_unlock_irqrestore(&lruvecs.vecs[i]->lru_lock, flags);
> }
> - if (lruvec)
> - unlock_page_lruvec_irqrestore(lruvec, flags);
> +
> release_pages(pvec->pages, pvec->nr);
> pagevec_reinit(pvec);
> }
>
next prev parent reply other threads:[~2020-11-25 15:38 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-20 8:27 [PATCH next] mm/swap.c: reduce lock contention in lru_cache_add Alex Shi
2020-11-20 23:19 ` Andrew Morton
2020-11-23 4:46 ` Alex Shi
2020-11-25 15:38 ` Vlastimil Babka [this message]
2020-11-26 3:12 ` Alex Shi
2020-11-26 11:05 ` Vlastimil Babka
2020-11-26 4:52 ` Yu Zhao
2020-11-26 6:39 ` Alex Shi
2020-11-26 7:24 ` Yu Zhao
2020-11-26 8:09 ` Alex Shi
2020-11-26 11:22 ` Vlastimil Babka
2020-11-26 15:44 ` Vlastimil Babka
2020-11-26 15:55 ` Matthew Wilcox
2020-11-27 3:14 ` Alex Shi
2020-12-01 8:02 ` [PATCH 1/3] mm/swap.c: pre-sort pages in pagevec for pagevec_lru_move_fn Alex Shi
2020-12-01 8:02 ` [PATCH 2/3] mm/swap.c: bail out early for no memcg and no numa Alex Shi
2020-12-01 8:02 ` [PATCH 3/3] mm/swap.c: extend the usage to pagevec_lru_add Alex Shi
2020-12-01 8:10 ` [PATCH 1/3] mm/swap.c: pre-sort pages in pagevec for pagevec_lru_move_fn Michal Hocko
2020-12-01 8:20 ` Alex Shi
2020-12-25 9:59 ` [RFC PATCH 0/4] pre sort pages on lruvec in pagevec Alex Shi
2020-12-25 9:59 ` [RFC PATCH 1/4] mm/swap.c: pre-sort pages in pagevec for pagevec_lru_move_fn Alex Shi
2020-12-25 9:59 ` [RFC PATCH 2/4] mm/swap.c: bail out early for no memcg and no numa Alex Shi
2020-12-25 9:59 ` [RFC PATCH 3/4] mm/swap.c: extend the usage to pagevec_lru_add Alex Shi
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