From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id 231066B024D for ; Tue, 27 Jul 2010 22:04:11 -0400 (EDT) Date: Wed, 28 Jul 2010 10:04:07 +0800 From: Wu Fengguang Subject: Re: [PATCH 2/6] writeback: reduce calls to global_page_state in balance_dirty_pages() Message-ID: <20100728020407.GA9819@localhost> References: <20100711020656.340075560@intel.com> <20100711021748.735126772@intel.com> <20100726151946.GH3280@quack.suse.cz> <20100727035941.GA15007@localhost> <20100727091220.GD3358@quack.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100727091220.GD3358@quack.suse.cz> Sender: owner-linux-mm@kvack.org To: Jan Kara Cc: Andrew Morton , Christoph Hellwig , Peter Zijlstra , Richard Kennedy , Dave Chinner , "linux-fsdevel@vger.kernel.org" , Linux Memory Management List , LKML List-ID: > > The global threshold check is added in place of clip_bdi_dirty_limit() > > for safety and not intended as a behavior change. If ever leading to > > big behavior change and regression, that it would be indicating some > > too permissive per-bdi threshold calculation. > > > > Did you see the global dirty threshold get exceeded when writing to 2+ > > devices? Occasional small exceeding should be OK though. I tried the > > following debug patch and see no warnings when doing two concurrent cp > > over local disk and NFS. > Oops, sorry. I've misread the code. You're right. There shouldn't be a big > change in the behavior. It does indicate a missing point in the changelog. The paragraph is updated to: We now set and clear dirty_exceeded not only based on bdi dirty limits, but also on the global dirty limit. The global limit check is added in place of clip_bdi_dirty_limit() for safety and not intended as a behavior change. The bdi limits should be tight enough to keep all dirty pages under the global limit at most time; occasional small exceeding should be OK though. The change makes the logic more obvious: the global limit is the ultimate goal and shall be always imposed. Thanks, Fengguang -- 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