From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755760Ab3BVDNf (ORCPT ); Thu, 21 Feb 2013 22:13:35 -0500 Received: from mail-qc0-f182.google.com ([209.85.216.182]:49121 "EHLO mail-qc0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753513Ab3BVDNc (ORCPT ); Thu, 21 Feb 2013 22:13:32 -0500 Message-ID: <5126E253.2030105@gmail.com> Date: Fri, 22 Feb 2013 11:13:23 +0800 From: Ric Mason User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130106 Thunderbird/17.0.2 MIME-Version: 1.0 To: Dan Magenheimer CC: Minchan Kim , Hugh Dickins , Nitin Gupta , Seth Jennings , Konrad Rzeszutek Wilk , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: Questin about swap_slot free and invalidate page References: <20130131051140.GB23548@blaptop> <20130204024950.GD2688@blaptop> <51236C11.1010208@gmail.com> <1f089254-3abe-4c63-a72a-c9e564ae7d0d@default> <51242F0D.4040201@gmail.com> <7793705b-a076-4c5a-be4d-9572d7560860@default> In-Reply-To: <7793705b-a076-4c5a-be4d-9572d7560860@default> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/22/2013 05:42 AM, Dan Magenheimer wrote: >> From: Ric Mason [mailto:ric.masonn@gmail.com] >> Subject: Re: Questin about swap_slot free and invalidate page >> >> On 02/19/2013 11:27 PM, Dan Magenheimer wrote: >>>> From: Ric Mason [mailto:ric.masonn@gmail.com] >>>>> Hugh is right that handling the possibility of duplicates is >>>>> part of the tmem ABI. If there is any possibility of duplicates, >>>>> the ABI defines how a backend must handle them to avoid data >>>>> coherency issues. >>>>> >>>>> The kernel implements an in-kernel API which implements the tmem >>>>> ABI. If the frontend and backend can always agree that duplicate >>>> Which ABI in zcache implement that? >>> https://oss.oracle.com/projects/tmem/dist/documentation/api/tmemspec-v001.pdf >>> >>> The in-kernel APIs are frontswap and cleancache. For more information about >>> tmem, see http://lwn.net/Articles/454795/ >> But you mentioned that you have in-kernel API which can handle >> duplicate. Do you mean zcache_cleancache/frontswap_put_page? I think >> they just overwrite instead of optional flush the page on the >> second(duplicate) put as mentioned in your tmemspec. > Maybe I am misunderstanding your question... The spec allows > overwrite (and return success) OR flush the page (and return > failure). Zcache does the latter (flush). The code that implements > it is in tmem_put. Thanks for your point out. Pers pages can have duplicate put since swap cache page can be reused. Can eph pages also have duplicate put? If yes, when can happen? >