Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S948240AbdDUAe2 (ORCPT ); Thu, 20 Apr 2017 20:34:28 -0400 Received: from mga09.intel.com ([134.134.136.24]:9848 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S948055AbdDUAeZ (ORCPT ); Thu, 20 Apr 2017 20:34:25 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.37,227,1488873600"; d="scan'208";a="848214432" From: "Huang\, Ying" To: Johannes Weiner Cc: "Huang\, Ying" , Andrew Morton , , Subject: Re: [PATCH -mm -v9 2/3] mm, THP, swap: Check whether THP can be split firstly References: <20170419070625.19776-1-ying.huang@intel.com> <20170419070625.19776-3-ying.huang@intel.com> <20170419161318.GC3376@cmpxchg.org> <87efwnrjfg.fsf@yhuang-dev.intel.com> <20170420205035.GA13229@cmpxchg.org> Date: Fri, 21 Apr 2017 08:34:22 +0800 In-Reply-To: <20170420205035.GA13229@cmpxchg.org> (Johannes Weiner's message of "Thu, 20 Apr 2017 16:50:35 -0400") Message-ID: <87r30mha41.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1759 Lines: 39 Johannes Weiner writes: > On Thu, Apr 20, 2017 at 08:50:43AM +0800, Huang, Ying wrote: >> Johannes Weiner writes: >> > On Wed, Apr 19, 2017 at 03:06:24PM +0800, Huang, Ying wrote: >> >> With the patchset, the swap out throughput improves 3.6% (from about >> >> 4.16GB/s to about 4.31GB/s) in the vm-scalability swap-w-seq test case >> >> with 8 processes. The test is done on a Xeon E5 v3 system. The swap >> >> device used is a RAM simulated PMEM (persistent memory) device. To >> >> test the sequential swapping out, the test case creates 8 processes, >> >> which sequentially allocate and write to the anonymous pages until the >> >> RAM and part of the swap device is used up. >> >> >> >> Cc: Johannes Weiner >> >> Signed-off-by: "Huang, Ying" >> >> Acked-by: Kirill A. Shutemov [for can_split_huge_page()] >> > >> > How often does this actually happen in practice? Because all that this >> > protects us from is trying to allocate a swap cluster - which with the >> > si->free_clusters list really isn't all that expensive - and return it >> > again. Unless this happens all the time in practice, this optimization >> > seems misplaced. >> >> To my surprise too, I found this patch has measurable impact in my >> test. The swap out throughput improves 3.6% in the vm-scalability >> swap-w-seq test case with 8 processes. Details are in the original >> patch description. > > Yeah I think that justifies it. > > The changelog says "the patchset", I didn't realize this is the gain > from just this patch alone. Care to update that? Sorry for confusing, will update it in the next version. Best Regards, Huang, Ying > Thanks!