From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: Re: [PATCH 5/5] PM/Hibernate: Do not release preallocated memory unnecessarily (rev. 2) Date: Tue, 5 May 2009 10:24:27 +0800 Message-ID: <20090505022427.GA10880__17252.9568350457$1241490563$gmane$org@localhost> References: <200905031830.49690.rjw@sisk.pl> <200905040208.43040.rjw@sisk.pl> <200905040222.39062.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <200905040222.39062.rjw@sisk.pl> 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: "Rafael J. Wysocki" 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 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) For you reference, here is the free memory before/after hibernate_preallocate_memory(): # free total used free shared buffers cached Mem: 1933 1917 15 0 0 1845 -/+ buffers/cache: 72 1861 Swap: 0 0 0 # free total used free shared buffers cached Mem: 1933 920 1012 0 0 356 -/+ buffers/cache: 563 1369 Swap: 0 0 0 It seems that the preallocated memory is not freed on -ENOMEM. + error = memory_bm_create(&orig_bm, GFP_IMAGE, PG_ANY); + if (error) + goto err_out; + + error = memory_bm_create(©_bm, GFP_IMAGE, PG_ANY); + if (error) + goto err_out; memory_bm_create() is called a number of times, each time it will call create_mem_extents()/memory_bm_free(). Can they be optimized to be called only once? A side note: there are somehow duplicated *_extent_*() logics in the filesystems, is it possible that we abstract out some of the common code? + for_each_populated_zone(zone) { + size += snapshot_additional_pages(zone); + count += zone_page_state(zone, NR_FREE_PAGES); + if (!is_highmem(zone)) + count -= zone->lowmem_reserve[ZONE_NORMAL]; + } Why [ZONE_NORMAL] instead of [zone]? ZONE_NORMAL may not always be the largest zone, for example, My 4GB laptop has a tiny ZONE_NORMAL and a large ZONE_DMA32. + /* If size < max_size, preallocating enough memory may be impossible. */ + if (count > 0 && size == max_size) + error = -ENOMEM; + if (error) + goto err_out; The two if()s can be merged. At last, I'd express my major concern about the transition to preallocate based memory shrinking: will it lead to more random swapping IOs? Thanks, Fengguang