From: Mel Gorman <mel@csn.ul.ie>
To: Minchan Kim <minchan.kim@gmail.com>
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 09:23:12 +0100 [thread overview]
Message-ID: <20100916082312.GA15709@csn.ul.ie> (raw)
In-Reply-To: <20100916075949.GA16115@barrios-desktop>
On Thu, Sep 16, 2010 at 04:59:49PM +0900, Minchan Kim wrote:
> 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.
>
My bad, when the description was first written, both were affected and I
neglected to correct the description. I'm still debating with myself as
to whether the kswapd congestion_wait() should be wait_iff_congested()
or not.
Thanks
> "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
>
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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next prev parent reply other threads:[~2010-09-16 8:23 UTC|newest]
Thread overview: 28+ 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 ` [PATCH 1/8] tracing, vmscan: Add trace events for LRU list shrinking Mel Gorman
2010-09-15 12:27 ` [PATCH 2/8] writeback: Account for time spent congestion_waited 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 ` [PATCH 4/8] vmscan: Narrow the scenarios lumpy reclaim uses synchrounous reclaim 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 ` [PATCH 6/8] vmscan: isolated_lru_pages() stop neighbour search if neighbour cannot be isolated 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
2010-09-16 7:59 ` Minchan Kim
2010-09-16 8:23 ` Mel Gorman [this message]
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
2010-09-16 8:13 ` Minchan Kim
2010-09-16 9:18 ` Mel Gorman
2010-09-16 14:11 ` Minchan Kim
2010-09-16 15:18 ` Mel Gorman
2010-09-16 22:28 ` Andrew Morton
2010-09-20 9:52 ` Mel Gorman
2010-09-21 21:44 ` Andrew Morton
2010-09-21 22:10 ` Mel Gorman
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
2010-09-16 22:28 ` [PATCH 0/8] Reduce latencies and improve overall reclaim efficiency v2 Andrew Morton
2010-09-17 7:52 ` Mel Gorman
2010-10-14 15:28 ` Christian Ehrhardt
2010-10-18 13:55 ` Mel Gorman
2010-10-22 12:29 ` Christian Ehrhardt
2010-11-03 10:50 ` Christian Ehrhardt
2010-11-10 14:37 ` Mel Gorman
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