Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423132AbWJYInZ (ORCPT ); Wed, 25 Oct 2006 04:43:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1423059AbWJYInZ (ORCPT ); Wed, 25 Oct 2006 04:43:25 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:12766 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S1423132AbWJYInY (ORCPT ); Wed, 25 Oct 2006 04:43:24 -0400 Date: Wed, 25 Oct 2006 10:42:26 +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: <20061025084226.GN5851@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1161764907.22729.86.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 Content-Length: 1430 Lines: 32 Hi! > > > With the code I have in Suspend2 (which is what I'm working towards), > > > the value includes the swap_type, so there's no overlap. Assuming the > > > swap allocator does it's normal thing and swap allocated is contiguous, > > > you'll probably end up with two extents: one containing the swap > > > allocated on the first device, and the other containing the swap > > > allocated on the second device. So (with the current version), striping > > > would use 6 * sizeof(unsigned long) instead of 3 * sizeof(unsigned > > > long). > > > > 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? And you do linear walks over those extents, leading to O(n^2) algorithm, no? That has bitten us before... Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/