Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752644Ab3EPPbO (ORCPT ); Thu, 16 May 2013 11:31:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19843 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752138Ab3EPPbN (ORCPT ); Thu, 16 May 2013 11:31:13 -0400 Message-ID: <5194FB9A.6000300@redhat.com> Date: Thu, 16 May 2013 11:30:34 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130402 Thunderbird/17.0.5 MIME-Version: 1.0 To: Seth Jennings CC: Andrew Morton , Greg Kroah-Hartman , Nitin Gupta , Minchan Kim , Konrad Rzeszutek Wilk , Dan Magenheimer , Robert Jennings , Jenifer Hopper , Mel Gorman , Johannes Weiner , Larry Woodman , Benjamin Herrenschmidt , Dave Hansen , Joe Perches , Joonsoo Kim , Cody P Schafer , Hugh Dickens , Paul Mackerras , linux-mm@kvack.org, linux-kernel@vger.kernel.org, devel@driverdev.osuosl.org Subject: Re: [PATCHv11 2/4] zbud: add to mm/ References: <1368448803-2089-1-git-send-email-sjenning@linux.vnet.ibm.com> <1368448803-2089-3-git-send-email-sjenning@linux.vnet.ibm.com> In-Reply-To: <1368448803-2089-3-git-send-email-sjenning@linux.vnet.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1541 Lines: 34 On 05/13/2013 08:40 AM, Seth Jennings wrote: > zbud is an special purpose allocator for storing compressed pages. It is > designed to store up to two compressed pages per physical page. While this > design limits storage density, it has simple and deterministic reclaim > properties that make it preferable to a higher density approach when reclaim > will be used. > > zbud works by storing compressed pages, or "zpages", together in pairs in a > single memory page called a "zbud page". The first buddy is "left > justifed" at the beginning of the zbud page, and the last buddy is "right > justified" at the end of the zbud page. The benefit is that if either > buddy is freed, the freed buddy space, coalesced with whatever slack space > that existed between the buddies, results in the largest possible free region > within the zbud page. > > zbud also provides an attractive lower bound on density. The ratio of zpages > to zbud pages can not be less than 1. This ensures that zbud can never "do > harm" by using more pages to store zpages than the uncompressed zpages would > have used on their own. > > This patch adds zbud to mm/ for later use by zswap. > > Signed-off-by: Seth Jennings Acked-by: Rik van Riel -- All rights reversed -- 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/