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From: Minchan Kim <minchan.kim@gmail.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	Linux Kernel List <linux-kernel@vger.kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Wu Fengguang <fengguang.wu@intel.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH 7/8] writeback: Do not sleep on the congestion queue if there are no congested BDIs
Date: Thu, 16 Sep 2010 16:59:49 +0900	[thread overview]
Message-ID: <20100916075949.GA16115@barrios-desktop> (raw)
In-Reply-To: <1284553671-31574-8-git-send-email-mel@csn.ul.ie>

On Wed, Sep 15, 2010 at 01:27:50PM +0100, Mel Gorman wrote:
> If congestion_wait() is called with no BDI congested, the caller will sleep
> for the full timeout and this may be an unnecessary sleep. This patch adds
> a wait_iff_congested() that checks congestion and only sleeps if a BDI is
> congested else, it calls cond_resched() to ensure the caller is not hogging
> the CPU longer than its quota but otherwise will not sleep.
> 
> This is aimed at reducing some of the major desktop stalls reported during
> IO. For example, while kswapd is operating, it calls congestion_wait()
> but it could just have been reclaiming clean page cache pages with no
> congestion. Without this patch, it would sleep for a full timeout but after
> this patch, it'll just call schedule() if it has been on the CPU too long.
> Similar logic applies to direct reclaimers that are not making enough
> progress.

I confused due to kswapd you mentioned.
This patch affects only direct reclaim.
Please, complete the description. 

"This patch affects direct reclaimer to reduce stall"
Otherwise, looks good to me. 

> 
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>

-- 
Kind regards,
Minchan Kim

WARNING: multiple messages have this Message-ID (diff)
From: Minchan Kim <minchan.kim@gmail.com>
To: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	Linux Kernel List <linux-kernel@vger.kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Wu Fengguang <fengguang.wu@intel.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Subject: Re: [PATCH 7/8] writeback: Do not sleep on the congestion queue if there are no congested BDIs
Date: Thu, 16 Sep 2010 16:59:49 +0900	[thread overview]
Message-ID: <20100916075949.GA16115@barrios-desktop> (raw)
In-Reply-To: <1284553671-31574-8-git-send-email-mel@csn.ul.ie>

On Wed, Sep 15, 2010 at 01:27:50PM +0100, Mel Gorman wrote:
> If congestion_wait() is called with no BDI congested, the caller will sleep
> for the full timeout and this may be an unnecessary sleep. This patch adds
> a wait_iff_congested() that checks congestion and only sleeps if a BDI is
> congested else, it calls cond_resched() to ensure the caller is not hogging
> the CPU longer than its quota but otherwise will not sleep.
> 
> This is aimed at reducing some of the major desktop stalls reported during
> IO. For example, while kswapd is operating, it calls congestion_wait()
> but it could just have been reclaiming clean page cache pages with no
> congestion. Without this patch, it would sleep for a full timeout but after
> this patch, it'll just call schedule() if it has been on the CPU too long.
> Similar logic applies to direct reclaimers that are not making enough
> progress.

I confused due to kswapd you mentioned.
This patch affects only direct reclaim.
Please, complete the description. 

"This patch affects direct reclaimer to reduce stall"
Otherwise, looks good to me. 

> 
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>

-- 
Kind regards,
Minchan Kim

--
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  reply	other threads:[~2010-09-16  7:59 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-09-15 12:27 [PATCH 0/8] Reduce latencies and improve overall reclaim efficiency v2 Mel Gorman
2010-09-15 12:27 ` Mel Gorman
2010-09-15 12:27 ` [PATCH 1/8] tracing, vmscan: Add trace events for LRU list shrinking Mel Gorman
2010-09-15 12:27   ` Mel Gorman
2010-09-15 12:27 ` [PATCH 2/8] writeback: Account for time spent congestion_waited Mel Gorman
2010-09-15 12:27   ` Mel Gorman
2010-09-15 12:27 ` [PATCH 3/8] vmscan: Synchronous lumpy reclaim should not call congestion_wait() Mel Gorman
2010-09-15 12:27   ` Mel Gorman
2010-09-15 12:27 ` [PATCH 4/8] vmscan: Narrow the scenarios lumpy reclaim uses synchrounous reclaim Mel Gorman
2010-09-15 12:27   ` Mel Gorman
2010-09-15 12:27 ` [PATCH 5/8] vmscan: Remove dead code in shrink_inactive_list() Mel Gorman
2010-09-15 12:27   ` Mel Gorman
2010-09-15 12:27 ` [PATCH 6/8] vmscan: isolated_lru_pages() stop neighbour search if neighbour cannot be isolated Mel Gorman
2010-09-15 12:27   ` Mel Gorman
2010-09-15 12:27 ` [PATCH 7/8] writeback: Do not sleep on the congestion queue if there are no congested BDIs Mel Gorman
2010-09-15 12:27   ` Mel Gorman
2010-09-16  7:59   ` Minchan Kim [this message]
2010-09-16  7:59     ` Minchan Kim
2010-09-16  8:23     ` Mel Gorman
2010-09-16  8:23       ` Mel Gorman
2010-09-15 12:27 ` [PATCH 8/8] writeback: Do not sleep on the congestion queue if there are no congested BDIs or if significant congestion is not being encountered in the current zone Mel Gorman
2010-09-15 12:27   ` Mel Gorman
2010-09-16  8:13   ` Minchan Kim
2010-09-16  8:13     ` Minchan Kim
2010-09-16  9:18     ` Mel Gorman
2010-09-16  9:18       ` Mel Gorman
2010-09-16 14:11       ` Minchan Kim
2010-09-16 14:11         ` Minchan Kim
2010-09-16 15:18         ` Mel Gorman
2010-09-16 15:18           ` Mel Gorman
2010-09-16 22:28   ` Andrew Morton
2010-09-16 22:28     ` Andrew Morton
2010-09-20  9:52     ` Mel Gorman
2010-09-20  9:52       ` Mel Gorman
2010-09-21 21:44       ` Andrew Morton
2010-09-21 21:44         ` Andrew Morton
2010-09-21 22:10         ` Mel Gorman
2010-09-21 22:10           ` Mel Gorman
2010-09-21 22:24           ` Andrew Morton
2010-09-21 22:24             ` Andrew Morton
2010-09-20 13:05   ` [PATCH] writeback: Do not sleep on the congestion queue if there are no congested BDIs or if significant congestion is not being encounted in the current zone fix Mel Gorman
2010-09-20 13:05     ` Mel Gorman
2010-09-16 22:28 ` [PATCH 0/8] Reduce latencies and improve overall reclaim efficiency v2 Andrew Morton
2010-09-16 22:28   ` Andrew Morton
2010-09-17  7:52   ` Mel Gorman
2010-09-17  7:52     ` Mel Gorman
2010-10-14 15:28 ` Christian Ehrhardt
2010-10-14 15:28   ` Christian Ehrhardt
2010-10-14 15:28   ` Christian Ehrhardt
2010-10-18 13:55   ` Mel Gorman
2010-10-18 13:55     ` Mel Gorman
2010-10-22 12:29     ` Christian Ehrhardt
2010-10-22 12:29       ` Christian Ehrhardt
2010-10-22 12:29       ` Christian Ehrhardt
2010-11-03 10:50     ` Christian Ehrhardt
2010-11-03 10:50       ` Christian Ehrhardt
2010-11-03 10:50       ` Christian Ehrhardt
2010-11-10 14:37       ` Mel Gorman
2010-11-10 14:37         ` Mel Gorman

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