From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [RESEND][PATCH -mm 2/2] vfs: add cond_resched_lock while scanning dentry LRU lists Date: Mon, 23 Jun 2008 19:11:40 -0700 Message-ID: <20080623191140.c0f15ee9.akpm@linux-foundation.org> References: <486051B3.4070903@np.css.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, viro@ZenIV.linux.org.uk, harvey.harrison@gmail.com To: Kentaro Makita Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:44912 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752040AbYFXCLn (ORCPT ); Mon, 23 Jun 2008 22:11:43 -0400 In-Reply-To: <486051B3.4070903@np.css.fujitsu.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, 24 Jun 2008 10:45:23 +0900 Kentaro Makita wrote: > o add cond_resched_lock(&dcache_lock) while scanning LRU lists on superblocks > in __shrink_dcache_sb() > > Signed-off-by: Kentaro Makita > --- > fs/dcache.c | 1 + > 1 files changed, 1 insertion(+) > > Index: b/fs/dcache.c > =================================================================== > --- a/fs/dcache.c 2008-06-05 11:48:57.000000000 +0900 > +++ b/fs/dcache.c 2008-06-05 11:49:19.000000000 +0900 > @@ -484,6 +484,7 @@ restart: > if (--cnt == 0) > break; > } > + cond_resched_lock(&dcache_lock); > } > } > while (!list_empty(&tmp)) { The changelog is insufficient. It tells us what the patch did (which was completely obvious anyway) but it fails to tell us _why_ the patch did it. That is is easily guessable but a good changelog would have described the problem which you observed and would have described how the the patch changed the runtime behaviour. And this is not a trivial formality either. Because if, for example, the problem whcih you are fixing here is "machine goes comatose for ten minutes" then we'll need algorithmic changes and not a bandaid of this nature.