linux-kernel - Re: [PATCH] mm: reduce spinlock contention in release

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Date:   Wed, 24 Nov 2021 15:57:58 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Hao Lee <haolee.swjtu@...il.com>
Cc:     linux-mm@...ck.org, hannes@...xchg.org, mhocko@...nel.org,
        vdavydov.dev@...il.com, shakeelb@...gle.com,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: reduce spinlock contention in release_pages()

On Wed, Nov 24, 2021 at 03:19:15PM +0000, Hao Lee wrote:
> When several tasks are terminated simultaneously, lots of pages will be
> released, which can cause severe spinlock contention. Other tasks which
> are running on the same core will be seriously affected. We can yield
> cpu to fix this problem.

The realtime people will eat you alive for this suggestion.

> +++ b/mm/swap.c
> @@ -960,8 +960,14 @@ void release_pages(struct page **pages, int nr)
>  		if (PageLRU(page)) {
>  			struct lruvec *prev_lruvec = lruvec;
>  
> -			lruvec = folio_lruvec_relock_irqsave(folio, lruvec,
> +retry:
> +			lruvec = folio_lruvec_tryrelock_irqsave(folio, lruvec,
>  									&flags);
> +			if (!lruvec) {
> +				cond_resched();
> +				goto retry;
> +			}
> +
>  			if (prev_lruvec != lruvec)