From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id ABA7C6B0069 for ; Thu, 5 Jan 2017 01:22:45 -0500 (EST) Received: by mail-pf0-f200.google.com with SMTP id 17so804615354pfy.2 for ; Wed, 04 Jan 2017 22:22:45 -0800 (PST) Received: from lgeamrelo11.lge.com (LGEAMRELO11.lge.com. [156.147.23.51]) by mx.google.com with ESMTP id g31si44264434pld.30.2017.01.04.22.22.44 for ; Wed, 04 Jan 2017 22:22:44 -0800 (PST) Date: Thu, 5 Jan 2017 15:15:57 +0900 From: Minchan Kim Subject: Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations Message-ID: <20170105061557.GD24371@bbox> References: <20161227074503.GA10616@bbox> <20170102154841.GG18058@quack2.suse.cz> <20170103043411.GA15657@bbox> <87inpwu29c.fsf@yhuang-dev.intel.com> MIME-Version: 1.0 In-Reply-To: <87inpwu29c.fsf@yhuang-dev.intel.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: "Huang, Ying" Cc: Jan Kara , Tim Chen , Andrew Morton , dave.hansen@intel.com, ak@linux.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 , Hillf Danton , Christian Borntraeger , Jonathan Corbet , Peter Zijlstra , Nicholas Piggin Hi Huang, On Tue, Jan 03, 2017 at 01:43:43PM +0800, Huang, Ying wrote: > Hi, Minchan, > > Minchan Kim writes: > > > Hi Jan, > > > > On Mon, Jan 02, 2017 at 04:48:41PM +0100, Jan Kara wrote: > >> Hi, > >> > >> On Tue 27-12-16 16:45:03, Minchan Kim wrote: > >> > > Patch 3 splits the swap cache radix tree into 64MB chunks, reducing > >> > > the rate that we have to contende for the radix tree. > >> > > >> > To me, it's rather hacky. I think it might be common problem for page cache > >> > so can we think another generalized way like range_lock? Ccing Jan. > >> > >> I agree on the hackyness of the patch and that page cache would suffer with > >> the same contention (although the files are usually smaller than swap so it > >> would not be that visible I guess). But I don't see how range lock would > >> help here - we need to serialize modifications of the tree structure itself > >> and that is difficult to achieve with the range lock. So what you would > >> need is either a different data structure for tracking swap cache entries > >> or a finer grained locking of the radix tree. > > > > Thanks for the comment, Jan. > > > > I think there are more general options. One is to shrink batching pages like > > Mel and Tim had approached. > > > > https://patchwork.kernel.org/patch/9008421/ > > https://patchwork.kernel.org/patch/9322793/ > > This helps to reduce the lock contention on radix tree of swap cache. > But splitting swap cache has much better performance. So we switched > from that solution to current solution. > > > Or concurrent page cache by peter. > > > > https://www.kernel.org/doc/ols/2007/ols2007v2-pages-311-318.pdf > > I think this is good, it helps swap and file cache. But I don't know > whether other people want to go this way and how much effort will be > needed. > > In contrast, splitting swap cache is quite simple, for implementation > and review. And the effect is good. I think general approach is better but I don't want to be a a party pooper if every people are okay with this. I just wanted to point out we need to consider more general approach and I did my best. Decision depends on you guys. 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