From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx108.postini.com [74.125.245.108]) by kanga.kvack.org (Postfix) with SMTP id 3D5AD6B004D for ; Wed, 11 Jan 2012 17:25:49 -0500 (EST) Received: by yhoo21 with SMTP id o21so719727yho.14 for ; Wed, 11 Jan 2012 14:25:48 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20237.63802.982209.699996@quad.stoffel.home> References: <20120109181023.7c81d0be@annuminas.surriel.com> <4F0B7D1F.7040802@gmail.com> <4F0BABE0.8080107@redhat.com> <20237.39051.575883.450826@quad.stoffel.home> <20237.63802.982209.699996@quad.stoffel.home> From: KOSAKI Motohiro Date: Wed, 11 Jan 2012 17:25:27 -0500 Message-ID: Subject: Re: [PATCH -mm] make swapin readahead skip over holes Content-Type: text/plain; charset=ISO-8859-1 Sender: owner-linux-mm@kvack.org List-ID: To: John Stoffel Cc: Christoph Lameter , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Mel Gorman , Johannes Weiner > Christoph> The assumptions by Kosaki are quite conservative. > > Just checking > > Christoph> What if one did not get a disk from the garbage heap but > Christoph> instead has a state of the art storage cluster or simply an > Christoph> SSD (in particular relevant now since HDs are in short > Christoph> supply given the situation in Asia)? > > I don't know, I was just trying to make sure he thinks about disks > which are slower than he expects, since there are lots of them still > out there. If you have a rotate disk, a bottoleneck is almost always IOPS, not disk bandwidth. at least when the systems are under swap-in, I can't imagine the system is under disk bandwidth neck. Therefore we can eat free lunch if and only if we don't increase number of IOs. In opposite, if you have much rich IO devices, that's more simple. You don't need worry about a few MB/s swap IO. -- 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