From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id D8A526B0069 for ; Mon, 2 Jan 2017 23:34:26 -0500 (EST) Received: by mail-pg0-f71.google.com with SMTP id a190so1206341611pgc.0 for ; Mon, 02 Jan 2017 20:34:26 -0800 (PST) Received: from lgeamrelo12.lge.com (LGEAMRELO12.lge.com. [156.147.23.52]) by mx.google.com with ESMTP id b72si67783641pli.151.2017.01.02.20.34.25 for ; Mon, 02 Jan 2017 20:34:26 -0800 (PST) Date: Tue, 3 Jan 2017 13:34:11 +0900 From: Minchan Kim Subject: Re: [PATCH v4 0/9] mm/swap: Regular page swap optimizations Message-ID: <20170103043411.GA15657@bbox> References: <20161227074503.GA10616@bbox> <20170102154841.GG18058@quack2.suse.cz> MIME-Version: 1.0 In-Reply-To: <20170102154841.GG18058@quack2.suse.cz> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: Tim Chen , Andrew Morton , Ying Huang , 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 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/ Or concurrent page cache by peter. https://www.kernel.org/doc/ols/2007/ols2007v2-pages-311-318.pdf Ccing Nick who might have an interest on lockless page cache. 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