From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx178.postini.com [74.125.245.178]) by kanga.kvack.org (Postfix) with SMTP id 51AFD6B005A for ; Mon, 9 Jan 2012 18:49:55 -0500 (EST) Received: by ggni2 with SMTP id i2so2255028ggn.14 for ; Mon, 09 Jan 2012 15:49:54 -0800 (PST) Message-ID: <4F0B7D1F.7040802@gmail.com> Date: Mon, 09 Jan 2012 18:49:51 -0500 From: KOSAKI Motohiro MIME-Version: 1.0 Subject: Re: [PATCH -mm] make swapin readahead skip over holes References: <20120109181023.7c81d0be@annuminas.surriel.com> In-Reply-To: <20120109181023.7c81d0be@annuminas.surriel.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Rik van Riel Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Mel Gorman , Johannes Weiner (1/9/12 6:10 PM), 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. If I understand correctly, this patch have Pros - increase IO throughput Cons - increase a risk to pick up unrelated swap entries by swap readahead The changelog explained former but doesn't explained latter. I'm a bit hesitate now. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org