Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756856Ab0HANlc (ORCPT ); Sun, 1 Aug 2010 09:41:32 -0400 Received: from mail-pv0-f174.google.com ([74.125.83.174]:40343 "EHLO mail-pv0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752328Ab0HANla (ORCPT ); Sun, 1 Aug 2010 09:41:30 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=szG9YTrJSim0znZ634a7hjofBH7ruHzWSoaPVctQX0Mbw7DwJiC0sb7kEHO5NR/TiV kRPLvVaN8adI6+ri/pAt5aehtlqBqRE9xlRtFLI1ujjAVoFOoMQaGVyKT9qywvJ7U4sC WySGYoqwSq/wvVMj4+Xj2NB7B4FTWc9emp6ys= Date: Sun, 1 Aug 2010 22:41:17 +0900 From: Minchan Kim To: KOSAKI Motohiro Cc: Wu Fengguang , Andrew Morton , Mel Gorman , Andy Whitcroft , Rik van Riel , Christoph Hellwig , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , Dave Chinner , Chris Mason , Nick Piggin , Johannes Weiner , KAMEZAWA Hiroyuki , Andrea Arcangeli , Andreas Mohr , Bill Davidsen , Ben Gamari Subject: Re: [PATCH] vmscan: synchronous lumpy reclaim don't call congestion_wait() Message-ID: <20100801134117.GA2034@barrios-desktop> References: <20100801085134.GA15577@localhost> <20100801180751.4B0E.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100801180751.4B0E.A69D9226@jp.fujitsu.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1913 Lines: 50 Hi KOSAKI, On Sun, Aug 01, 2010 at 06:12:47PM +0900, KOSAKI Motohiro wrote: > rebased onto Wu's patch > > ---------------------------------------------- > From 35772ad03e202c1c9a2252de3a9d3715e30d180f Mon Sep 17 00:00:00 2001 > From: KOSAKI Motohiro > Date: Sun, 1 Aug 2010 17:23:41 +0900 > Subject: [PATCH] vmscan: synchronous lumpy reclaim don't call congestion_wait() > > congestion_wait() mean "waiting for number of requests in IO queue is > under congestion threshold". > That said, if the system have plenty dirty pages, flusher thread push > new request to IO queue conteniously. So, IO queue are not cleared > congestion status for a long time. thus, congestion_wait(HZ/10) is > almostly equivalent schedule_timeout(HZ/10). Just a nitpick. Why is it a problem? HZ/10 is upper bound we intended. If is is rahter high, we can low it. But totally I agree on this patch. It would be better to remove it than lowing. > > If the system 512MB memory, DEF_PRIORITY mean 128kB scan and It takes 4096 > shrink_page_list() calls to scan 128kB (i.e. 128kB/32=4096) memory. > 4096 times 0.1sec stall makes crazy insane long stall. That shouldn't. 128K / (4K * SWAP_CLUSTER_MAX) = 1 > > In the other hand, this synchronous lumpy reclaim donesn't need this > congestion_wait() at all. shrink_page_list(PAGEOUT_IO_SYNC) cause to > call wait_on_page_writeback() and it provide sufficient waiting. Absolutely I agree on you. > > Signed-off-by: KOSAKI Motohiro > Reviewed-by: Wu Fengguang Reviewed-by: Minchan Kim -- Kind regards, Minchan Kim -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/