From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f44.google.com (mail-pa0-f44.google.com [209.85.220.44]) by kanga.kvack.org (Postfix) with ESMTP id EFE746B0035 for ; Wed, 30 Jul 2014 19:46:01 -0400 (EDT) Received: by mail-pa0-f44.google.com with SMTP id eu11so2434469pac.31 for ; Wed, 30 Jul 2014 16:46:01 -0700 (PDT) Received: from lgeamrelo02.lge.com (lgeamrelo02.lge.com. [156.147.1.126]) by mx.google.com with ESMTP id se3si3875670pac.228.2014.07.30.16.45.59 for ; Wed, 30 Jul 2014 16:46:00 -0700 (PDT) Message-ID: <53D983B5.3020903@lge.com> Date: Thu, 31 Jul 2014 08:45:57 +0900 From: Gioh Kim MIME-Version: 1.0 Subject: Re: [PATCH 0/2] new API to allocate buffer-cache for superblock in non-movable area References: <53CDF437.4090306@lge.com> <20140722073005.GT3935@laptop> <20140722093838.GA22331@quack.suse.cz> <53D8A258.7010904@lge.com> <20140730101143.GB19205@quack.suse.cz> <20140730101920.GI19379@twins.programming.kicks-ass.net> In-Reply-To: <20140730101920.GI19379@twins.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra , Jan Kara Cc: Alexander Viro , Andrew Morton , "Paul E. McKenney" , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Theodore Ts'o , Andreas Dilger , linux-ext4@vger.kernel.org, linux-mm@kvack.org, Minchan Kim , Joonsoo Kim 2014-07-30 i??i?? 7:19, Peter Zijlstra i?' e,?: > On Wed, Jul 30, 2014 at 12:11:43PM +0200, Jan Kara wrote: >>> sb_bread allocates page from movable area but it is not movable until the >>> reference counter of the buffer-head becomes zero. >>> There is no lock for the buffer but the reference counter acts like lock. >> OK, but why do you care about a single page (of at most handful if you >> have more filesystems) which isn't movable? That shouldn't make a big >> difference to compaction... > > The thing is, CMA _must_ be able to clear all the pages in its range, > otherwise its broken. > > So placing nonmovable pages in a movable block utterly wrecks that. YES. Even a single page can make CMA migration fail. > > Now, Ted said that there's more effectively pinned stuff from > filesystems (and I imagine those would be things like the root inode > etc.) and those would equally wreck this.. > > But Gioh didn't mention any of that.. he should I suppose. Thanks to inform me. I thought there are more pinned stuff but I didn't know what they are. I tried CMA migration but it failed even after I moved the sb page-cache to non-movable area. So I just guessed there are more pinned stuff. I am newbie and not familiar with filesystem code. Of course all of the pinned stuff should be moved to non-movable area. > -- 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