From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750767AbdAWHN2 (ORCPT ); Mon, 23 Jan 2017 02:13:28 -0500 Received: from mail-pg0-f65.google.com ([74.125.83.65]:36411 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750703AbdAWHN1 (ORCPT ); Mon, 23 Jan 2017 02:13:27 -0500 Date: Mon, 23 Jan 2017 16:13:39 +0900 From: Sergey Senozhatsky To: Joonsoo Kim Cc: Sergey Senozhatsky , zhouxianrong , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, sergey.senozhatsky@gmail.com, minchan@kernel.org, ngupta@vflare.org, Mi.Sophia.Wang@huawei.com, zhouxiyu@huawei.com, weidu.du@huawei.com, zhangshiming5@huawei.com, won.ho.park@huawei.com Subject: Re: [PATCH] mm: extend zero pages to same element pages for zram Message-ID: <20170123071339.GD2327@jagdpanzerIV.localdomain> References: <1483692145-75357-1-git-send-email-zhouxianrong@huawei.com> <1484296195-99771-1-git-send-email-zhouxianrong@huawei.com> <20170121084338.GA405@jagdpanzerIV.localdomain> <84073d07-6939-b22d-8bda-4fa2a9127555@huawei.com> <20170123025826.GA24581@js1304-P5Q-DELUXE> <20170123040347.GA2327@jagdpanzerIV.localdomain> <20170123062716.GF24581@js1304-P5Q-DELUXE> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170123062716.GF24581@js1304-P5Q-DELUXE> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (01/23/17 15:27), Joonsoo Kim wrote: > Hello, > > Think about following case in 64 bits kernel. > > If value pattern in the page is like as following, we cannot detect > the same page with 'unsigned int' element. > > AAAAAAAABBBBBBBBAAAAAAAABBBBBBBB... > > 4 bytes is 0xAAAAAAAA and next 4 bytes is 0xBBBBBBBB and so on. yep, that's exactly the case that I though would be broken with a 4-bytes pattern matching. so my conlusion was that for 4 byte pattern we would have working detection anyway, for 8 bytes patterns we might have some extra matching. not sure if it matters that much though. -ss