From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f199.google.com (mail-wr0-f199.google.com [209.85.128.199]) by kanga.kvack.org (Postfix) with ESMTP id 20A276B03B2 for ; Thu, 20 Apr 2017 16:50:44 -0400 (EDT) Received: by mail-wr0-f199.google.com with SMTP id v52so6846948wrb.14 for ; Thu, 20 Apr 2017 13:50:44 -0700 (PDT) Received: from gum.cmpxchg.org (gum.cmpxchg.org. [85.214.110.215]) by mx.google.com with ESMTPS id k88si11020844wrc.30.2017.04.20.13.50.42 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 20 Apr 2017 13:50:42 -0700 (PDT) Date: Thu, 20 Apr 2017 16:50:35 -0400 From: Johannes Weiner Subject: Re: [PATCH -mm -v9 2/3] mm, THP, swap: Check whether THP can be split firstly Message-ID: <20170420205035.GA13229@cmpxchg.org> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87efwnrjfg.fsf@yhuang-dev.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Huang, Ying" Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org 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? Thanks! -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org