From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933893Ab2AKVEa (ORCPT ); Wed, 11 Jan 2012 16:04:30 -0500 Received: from Mycroft.westnet.com ([216.187.52.7]:43572 "EHLO mycroft.westnet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751176Ab2AKVE3 (ORCPT ); Wed, 11 Jan 2012 16:04:29 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <20237.63802.982209.699996@quad.stoffel.home> Date: Wed, 11 Jan 2012 16:03:54 -0500 From: "John Stoffel" To: Christoph Lameter Cc: John Stoffel , KOSAKI Motohiro , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Mel Gorman , Johannes Weiner Subject: Re: [PATCH -mm] make swapin readahead skip over holes In-Reply-To: References: <20120109181023.7c81d0be@annuminas.surriel.com> <4F0B7D1F.7040802@gmail.com> <4F0BABE0.8080107@redhat.com> <20237.39051.575883.450826@quad.stoffel.home> X-Mailer: VM 8.1.1 under 23.2.1 (x86_64-pc-linux-gnu) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>>>> "Christoph" == Christoph Lameter writes: Christoph> On Wed, 11 Jan 2012, John Stoffel wrote: KOSAKI> so, we can eat free lunch up to 7MB ~= 60(MB/sec) * 1000 / 8.5(ms). >> >> What if the disk is busy doing other writeout or readin during this >> time? You can't assume you have the full disk bandwidth available, >> esp when you hit a swap storm like this. 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. John