From: Theodore Ts'o Subject: Re: [PATCHv4 0/3] new APIs to allocate buffer-cache with user specific flag Date: Thu, 4 Sep 2014 23:17:35 -0400 Message-ID: <20140905031735.GD1971@thunk.org> References: <1409815781-28011-1-git-send-email-gioh.kim@lge.com> <20140904151612.7bf5b813069ff78973e01571@linux-foundation.org> <540905B1.1050200@lge.com> <20140905011419.GE4364@thunk.org> <20140905014808.GA26070@js1304-P5Q-DELUXE> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Gioh Kim , Andrew Morton , jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, paulmck@linux.vnet.ibm.com, peterz@infradead.org, adilger.kernel@dilger.ca, minchan@kernel.org, gunho.lee@lge.com To: Joonsoo Kim Return-path: Content-Disposition: inline In-Reply-To: <20140905014808.GA26070@js1304-P5Q-DELUXE> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Joonson, Thanks for the update. I've applied Gioh's patches to the ext4 tree, but I'd appreciate a further clarification. My understanding with the problem you were trying to address is that with the current CMA implementation, kswapd was getting activiated too early, yes? But it would still be a good idea to try to use non-moveable memory in preference in favor of CMA memory; even if the page migration can move the contents of the page elsewhere, wouldn't be better to avoid needing to do the page migation in the first place. Given that the ext4 file systems are getting mounted very early in the boot process, when there should be plenty of CMA and non-CMA elegible memory available, why was CMA memory getting selected for the buffer cache allocations when non-CMA memory available? In other words, even without Gioh's patch to force the use of non-CMA eligible memory, wouldn't it be better if the memory allocator used non-CMA preferentially if it were available. This should be orthogonal to whether or not kswaped gets activiated, right? Regards, - Ted