From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx116.postini.com [74.125.245.116]) by kanga.kvack.org (Postfix) with SMTP id 5921F6B13F3 for ; Fri, 10 Feb 2012 00:52:25 -0500 (EST) Received: by vbip1 with SMTP id p1so2280647vbi.14 for ; Thu, 09 Feb 2012 21:52:24 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <20120208093120.GA18993@localhost> From: Greg Thelen Date: Thu, 9 Feb 2012 21:52:03 -0800 Message-ID: Subject: Re: memcg writeback (was Re: [Lsf-pc] [LSF/MM TOPIC] memcg topics.) Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: Wu Fengguang Cc: KAMEZAWA Hiroyuki , linux-mm@kvack.org, "hannes@cmpxchg.org" , Michal Hocko , "bsingharora@gmail.com" , Hugh Dickins , Ying Han , Mel Gorman (removed lsf-pc@lists.linux-foundation.org because this really isn't program committee matter) On Wed, Feb 1, 2012 at 11:52 PM, Wu Fengguang wrote: > Unfortunately the memcg partitioning could fundamentally make the > dirty throttling more bumpy. > > Imagine 10 memcgs each with > > - memcg_dirty_limit=50MB > - 1 dd dirty task > > The flusher thread will be working on 10 inodes in turn, each time > grabbing the next inode and taking ~0.5s to write ~50MB of its dirty > pages to the disk. So each inode will be flushed on every ~5s. Does the flusher thread need to write 50MB/inode in this case? Would there be problems interleaving writes by declaring some max write limit (e.g. 8 MiB/write). Such interleaving would be beneficial if there are multiple memcg expecting service from the single bdi flusher thread. I suspect certain filesystems might have increased fragmentation with this, but I am not sure if appending writes can easily expand an extent. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org