From mboxrd@z Thu Jan 1 00:00:00 1970 From: Minchan Kim 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 Message-ID: <20100916075949.GA16115@barrios-desktop> References: <1284553671-31574-1-git-send-email-mel@csn.ul.ie> <1284553671-31574-8-git-send-email-mel@csn.ul.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andrew Morton , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Linux Kernel List , Johannes Weiner , Wu Fengguang , KAMEZAWA Hiroyuki , KOSAKI Motohiro To: Mel Gorman Return-path: Content-Disposition: inline In-Reply-To: <1284553671-31574-8-git-send-email-mel@csn.ul.ie> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org 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 Reviewed-by: Minchan Kim -- Kind regards, Minchan Kim -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org