From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934039Ab2AKVbH (ORCPT ); Wed, 11 Jan 2012 16:31:07 -0500 Received: from mx1.redhat.com ([209.132.183.28]:1028 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932654Ab2AKVbC (ORCPT ); Wed, 11 Jan 2012 16:31:02 -0500 Message-ID: <4F0DFF64.4040704@redhat.com> Date: Wed, 11 Jan 2012 16:30:12 -0500 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20110930 Thunderbird/7.0.1 MIME-Version: 1.0 To: Johannes Weiner CC: linux-mm@kvack.org, linux-kernel@vger.kernel.org, KOSAKI Motohiro , akpm@linux-foundation.org, mel@csn.ul.ie, minchan.kim@gmail.com Subject: Re: [PATCH v2 -mm] make swapin readahead skip over holes References: <20120111143044.3c538d46@cuia.bos.redhat.com> <20120111205041.GE24386@cmpxchg.org> In-Reply-To: <20120111205041.GE24386@cmpxchg.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/11/2012 04:10 PM, Johannes Weiner wrote: > On Wed, Jan 11, 2012 at 02:30:44PM -0500, Rik van Riel wrote: >> Ever since abandoning the virtual scan of processes, for scalability >> reasons, swap space has been a little more fragmented than before. >> This can lead to the situation where a large memory user is killed, >> swap space ends up full of "holes" and swapin readahead is totally >> ineffective. >> >> On my home system, after killing a leaky firefox it took over an >> hour to page just under 2GB of memory back in, slowing the virtual >> machines down to a crawl. >> >> This patch makes swapin readahead simply skip over holes, instead >> of stopping at them. This allows the system to swap things back in >> at rates of several MB/second, instead of a few hundred kB/second. >> >> The checks done in valid_swaphandles are already done in >> read_swap_cache_async as well, allowing us to remove a fair amount >> of code. > > __swap_duplicate() also checks for whether the offset is within the > swap device range. Do you think we could remove get_swap_cluster() > altogether and just try reading the aligned page_cluster range? That is how I implemented it originally, but we need to take the swap_lock so it is cleaner to implement a helper function in swapfile.c :)