From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id E12416B02A3 for ; Mon, 12 Jul 2010 18:23:46 -0400 (EDT) Date: Mon, 12 Jul 2010 15:22:54 -0700 From: Andrew Morton Subject: Re: [PATCH 6/6] writeback: merge for_kupdate and !for_kupdate cases Message-Id: <20100712152254.2071ba5f.akpm@linux-foundation.org> In-Reply-To: <20100712155239.GC30222@localhost> References: <20100711020656.340075560@intel.com> <20100711021749.303817848@intel.com> <20100712020842.GC25335@dastard> <20100712155239.GC30222@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Wu Fengguang Cc: Dave Chinner , Christoph Hellwig , Martin Bligh , Michael Rubin , Peter Zijlstra , Jan Kara , Peter Zijlstra , "linux-fsdevel@vger.kernel.org" , Linux Memory Management List , LKML List-ID: On Mon, 12 Jul 2010 23:52:39 +0800 Wu Fengguang wrote: > > Also, I'd prefer that the > > comments remain somewhat more descriptive of the circumstances that > > we are operating under. Comments like "retry later to avoid blocking > > writeback of other inodes" is far, far better than "retry later" > > because it has "why" component that explains the reason for the > > logic. You may remember why, but I sure won't in a few months time.... me2 (of course). This code is waaaay too complex to be scrimping on comments. > Ah yes the comment is too simple. However the redirty_tail() is not to > avoid blocking writeback of other inodes, but to avoid eating 100% CPU > on busy retrying a dirty inode/page that cannot perform writeback for > a while. (In theory redirty_tail() can still busy retry though, when > there is only one single dirty inode.) So how about > > /* > * somehow blocked: avoid busy retrying > */ That's much too short. Expand on the "somehow" - provide an example, describe the common/expected cause. Fully explain what the "busy" retry _is_ and how it can come about. -- 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