From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753082AbcIIPxq (ORCPT ); Fri, 9 Sep 2016 11:53:46 -0400 Received: from mga09.intel.com ([134.134.136.24]:50531 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751618AbcIIPxn (ORCPT ); Fri, 9 Sep 2016 11:53:43 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.30,305,1470726000"; d="scan'208";a="876884961" Message-ID: <1473436422.3916.3.camel@linux.intel.com> Subject: Re: [PATCH -v3 00/10] THP swap: Delay splitting THP during swapping out From: Tim Chen To: Minchan Kim , "Huang, Ying" Cc: Andrew Morton , tim.c.chen@intel.com, dave.hansen@intel.com, andi.kleen@intel.com, aaron.lu@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hugh Dickins , Shaohua Li , Rik van Riel , Andrea Arcangeli , "Kirill A . Shutemov" , Vladimir Davydov , Johannes Weiner , Michal Hocko Date: Fri, 09 Sep 2016 08:53:42 -0700 In-Reply-To: <20160909054336.GA2114@bbox> References: <1473266769-2155-1-git-send-email-ying.huang@intel.com> <20160909054336.GA2114@bbox> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.5.2 (3.18.5.2-1.fc23) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2016-09-09 at 14:43 +0900, Minchan Kim wrote: > Hi Huang, > > On Wed, Sep 07, 2016 at 09:45:59AM -0700, Huang, Ying wrote: > > > > From: Huang Ying > > > > This patchset is to optimize the performance of Transparent Huge Page > > (THP) swap. > > > > Hi, Andrew, could you help me to check whether the overall design is > > reasonable? > > > > Hi, Hugh, Shaohua, Minchan and Rik, could you help me to review the > > swap part of the patchset?  Especially [01/10], [04/10], [05/10], > > [06/10], [07/10], [10/10]. > > > > Hi, Andrea and Kirill, could you help me to review the THP part of the > > patchset?  Especially [02/10], [03/10], [09/10] and [10/10]. > > > > Hi, Johannes, Michal and Vladimir, I am not very confident about the > > memory cgroup part, especially [02/10] and [03/10].  Could you help me > > to review it? > > > > And for all, Any comment is welcome! > > > > > > Recently, the performance of the storage devices improved so fast that > > we cannot saturate the disk bandwidth when do page swap out even on a > > high-end server machine.  Because the performance of the storage > > device improved faster than that of CPU.  And it seems that the trend > > will not change in the near future.  On the other hand, the THP > > becomes more and more popular because of increased memory size.  So it > > becomes necessary to optimize THP swap performance. > > > > The advantages of the THP swap support include: > > > > - Batch the swap operations for the THP to reduce lock > >   acquiring/releasing, including allocating/freeing the swap space, > >   adding/deleting to/from the swap cache, and writing/reading the swap > >   space, etc.  This will help improve the performance of the THP swap. > > > > - The THP swap space read/write will be 2M sequential IO.  It is > >   particularly helpful for the swap read, which usually are 4k random > >   IO.  This will improve the performance of the THP swap too. > > > > - It will help the memory fragmentation, especially when the THP is > >   heavily used by the applications.  The 2M continuous pages will be > >   free up after THP swapping out. > I just read patchset right now and still doubt why the all changes > should be coupled with THP tightly. Many parts(e.g., you introduced > or modifying existing functions for making them THP specific) could > just take page_list and the number of pages then would handle them > without THP awareness. > > For example, if the nr_pages is larger than SWAPFILE_CLUSTER, we > can try to allocate new cluster. With that, we could allocate new > clusters to meet nr_pages requested or bail out if we fail to allocate > and fallback to 0-order page swapout. With that, swap layer could > support multiple order-0 pages by batch. > > IMO, I really want to land Tim Chen's batching swapout work first. > With Tim Chen's work, I expect we can make better refactoring > for batching swap before adding more confuse to the swap layer. > (I expect it would share several pieces of code for or would be base > for batching allocation of swapcache, swapslot) Minchan, Ying and I do plan to send out a new patch series on batching swapout and swapin plus a few other optimization on the swapping of  regular sized pages. Hopefully we'll be able to do that soon after we fixed up a few things and retest. Tim