From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423143AbWJYJKk (ORCPT ); Wed, 25 Oct 2006 05:10:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1423145AbWJYJKk (ORCPT ); Wed, 25 Oct 2006 05:10:40 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:14557 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S1423143AbWJYJKj (ORCPT ); Wed, 25 Oct 2006 05:10:39 -0400 Date: Wed, 25 Oct 2006 11:10:22 +0200 From: Pavel Machek To: Nigel Cunningham Cc: "Rafael J. Wysocki" , Andrew Morton , LKML Subject: Re: [PATCH] Use extents for recording what swap is allocated. Message-ID: <20061025091022.GB7266@elf.ucw.cz> References: <1161576857.3466.9.camel@nigel.suspend2.net> <200610242208.34426.rjw@sisk.pl> <20061024213402.GC5662@elf.ucw.cz> <1161728153.22729.22.camel@nigel.suspend2.net> <20061024221950.GB5851@elf.ucw.cz> <1161729027.22729.37.camel@nigel.suspend2.net> <20061025081135.GM5851@elf.ucw.cz> <1161764907.22729.86.camel@nigel.suspend2.net> <20061025084226.GN5851@elf.ucw.cz> <1161766865.22729.96.camel@nigel.suspend2.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1161766865.22729.96.camel@nigel.suspend2.net> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > > > And now, can you do same computation assuming the swap allocator goes > > > > completely crazy, and free space is in 1-page chunks? > > > > > > The worst case is 3 * sizeof(unsigned long) * > > > number_of_swap_extents_allocated bytes. > > > > Okay, so if we got 4GB of swap space, thats 1MB swap pages, worst case > > is you have one extent per page, on x86-64 that's 24MB. +kmalloc > > overhead, I assume? > > Sounds right. Ok, 24-50MB per 4GB of swap space is not _that_ bad... > > And you do linear walks over those extents, leading to O(n^2) > > algorithm, no? That has bitten us before... > > We start from where we last added an extent on the chain by default. ...but linear search through 24MB _is_ going to hurt. > You're not going to respond to the other bit of my reply? I was > beginning to think you were being more reasonable this time. Oh well. Rafael likes your code, and that's a big plus, but do you have to insult me?! Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html