linux-kernel - Re: [RFC 2/3] mm: throttle on IO only when there are too many dirty and writeback pages

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Date:	Fri, 30 Oct 2015 12:18:50 +0800
From:	"Hillf Danton" <hillf.zj@...baba-inc.com>
To:	<mhocko@...nel.org>, <linux-mm@...ck.org>
Cc:	"'Andrew Morton'" <akpm@...ux-foundation.org>,
	"'Linus Torvalds'" <torvalds@...ux-foundation.org>,
	"'Mel Gorman'" <mgorman@...e.de>,
	"'Johannes Weiner'" <hannes@...xchg.org>,
	"'Rik van Riel'" <riel@...hat.com>,
	"'David Rientjes'" <rientjes@...gle.com>,
	"'Tetsuo Handa'" <penguin-kernel@...ove.SAKURA.ne.jp>,
	"'LKML'" <linux-kernel@...r.kernel.org>,
	"'Michal Hocko'" <mhocko@...e.com>,
	"Christoph Lameter" <cl@...ux.com>
Subject: Re: [RFC 2/3] mm: throttle on IO only when there are too many dirty and writeback pages


> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3191,8 +3191,23 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>  		 */
>  		if (__zone_watermark_ok(zone, order, min_wmark_pages(zone),
>  				ac->high_zoneidx, alloc_flags, target)) {
> -			/* Wait for some write requests to complete then retry */
> -			wait_iff_congested(zone, BLK_RW_ASYNC, HZ/50);
> +			unsigned long writeback = zone_page_state(zone, NR_WRITEBACK),
> +				      dirty = zone_page_state(zone, NR_FILE_DIRTY);
> +
> +			if (did_some_progress)
> +				goto retry;
> +
> +			/*
> +			 * If we didn't make any progress and have a lot of
> +			 * dirty + writeback pages then we should wait for
> +			 * an IO to complete to slow down the reclaim and
> +			 * prevent from pre mature OOM
> +			 */
> +			if (2*(writeback + dirty) > reclaimable)
> +				congestion_wait(BLK_RW_ASYNC, HZ/10);
> +			else
> +				cond_resched();
> +

Looks the vmstat updater issue is not addressed.
>  			goto retry;
>  		}
>  	}
> --
> 2.6.1

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