From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [PATCH 5/5] PM/Hibernate: Do not release preallocated memory unnecessarily (rev. 2) Date: Thu, 7 May 2009 14:20:42 +0200 Message-ID: <200905071420.43491.rjw__30528.6453491592$1241698957$gmane$org@sisk.pl> References: <200905062254.10227.rjw@sisk.pl> <20090507015803.GA12281@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20090507015803.GA12281@localhost> Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.linux-foundation.org Errors-To: linux-pm-bounces@lists.linux-foundation.org To: Wu Fengguang Cc: "linux-kernel@vger.kernel.org" , "alan-jenkins@tuffmail.co.uk" , "jens.axboe@oracle.com" , "linux-pm@lists.linux-foundation.org" , "kernel-testers@vger.kernel.org" , "torvalds@linux-foundation.org" , Andrew Morton List-Id: linux-pm@vger.kernel.org On Thursday 07 May 2009, Wu Fengguang wrote: > On Thu, May 07, 2009 at 04:54:09AM +0800, Rafael J. Wysocki wrote: > > On Wednesday 06 May 2009, Wu Fengguang wrote: > > > On Wed, May 06, 2009 at 07:05:09AM +0800, Rafael J. Wysocki wrote: > > > > On Tuesday 05 May 2009, Wu Fengguang wrote: > > > > > On Mon, May 04, 2009 at 08:22:38AM +0800, Rafael J. Wysocki wrote: > > > > > > From: Rafael J. Wysocki > > > > > > > > > > > > Since the hibernation code is now going to use allocations of memory > > > > > > to create enough room for the image, it can also use the page frames > > > > > > allocated at this stage as image page frames. The low-level > > > > > > hibernation code needs to be rearranged for this purpose, but it > > > > > > allows us to avoid freeing a great number of pages and allocating > > > > > > these same pages once again later, so it generally is worth doing. > > > > > > > > > > > > [rev. 2: Change the strategy of preallocating memory to allocate as > > > > > > many pages as needed to get the right image size in one shot (the > > > > > > excessive allocated pages are released afterwards).] > > > > > > > > > > Rafael, I tried out your patches and found doubled memory shrink speed! > > > > > > > > > > [ 579.641781] PM: Preallocating image memory ... done (allocated 383900 pages, 128000 image pages kept) > > > > > [ 583.087875] PM: Allocated 1535600 kbytes in 3.43 seconds (447.69 MB/s) > > > > > > > > Unfortunately, I'm observing a regression and a huge one. > > > > > > > > On my Atom-based test box with 1 GB of RAM after a fresh boot and starting X > > > > with KDE 4 there are ~256 MB free. To create an image we need to free ~300 MB > > > > and that takes ~2 s with the old code and ~15 s with the new one. > > > > > > > > It helps to call shrink_all_memory() once with a sufficiently large argument > > > > before the preallocation. > > > [snip] > > > > > At last, I'd express my major concern about the transition to preallocate > > > > > based memory shrinking: will it lead to more random swapping IOs? > > > > > > > > Hmm. I don't see immediately why would it. Maybe the regression I'm seeing > > > > is related to that ... > > > > > > So you do have swap file enabled? hibernate_preallocate_memory() will > > > firstly try to allocate as much pages as possible(savable+free), and > > > then to free up (allocated-image_size) pages. > > > > No. It's going to allocate (total RAM - anticipated image size) and then free > > up (allocated-image_size) pages. > > Ah yes - I didn't notice that count was subtracted here: > > for (count -= size; count > 0; count--) { > > Make "count -= size" a standalone line to make that more obvious? That should be clear in the new patches: http://patchwork.kernel.org/patch/22193/ http://patchwork.kernel.org/patch/22191/ Thanks, Rafael