From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx170.postini.com [74.125.245.170]) by kanga.kvack.org (Postfix) with SMTP id BFBE06B0032 for ; Thu, 15 Aug 2013 22:02:30 -0400 (EDT) Received: from /spool/local by e23smtp03.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 16 Aug 2013 11:51:32 +1000 Received: from d23relay04.au.ibm.com (d23relay04.au.ibm.com [9.190.234.120]) by d23dlp03.au.ibm.com (Postfix) with ESMTP id 9749F3578057 for ; Fri, 16 Aug 2013 12:02:20 +1000 (EST) Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay04.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r7G1kLig7602596 for ; Fri, 16 Aug 2013 11:46:29 +1000 Received: from d23av04.au.ibm.com (loopback [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r7G22ASJ017044 for ; Fri, 16 Aug 2013 12:02:12 +1000 Date: Fri, 16 Aug 2013 10:02:08 +0800 From: Wanpeng Li Subject: Re: [PATCH v6 0/5] zram/zsmalloc promotion Message-ID: <20130816020208.GA21147@hacker.(null)> Reply-To: Wanpeng Li References: <1376459736-7384-1-git-send-email-minchan@kernel.org> <20130814161753.GB2706@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130814161753.GB2706@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Luigi Semenzato , Greg Kroah-Hartman , Andrew Morton , Jens Axboe , Seth Jennings , Nitin Gupta , Konrad Rzeszutek Wilk , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Pekka Enberg , Mel Gorman Hi Minchan, On Thu, Aug 15, 2013 at 01:17:53AM +0900, Minchan Kim wrote: >Hi Luigi, > >On Wed, Aug 14, 2013 at 08:53:31AM -0700, Luigi Semenzato wrote: >> During earlier discussions of zswap there was a plan to make it work >> with zsmalloc as an option instead of zbud. Does zbud work for > >AFAIR, it was not an optoin but zsmalloc was must but there were >several objections because zswap's notable feature is to dump >compressed object to real swap storage. For that, zswap needs to >store bounded objects in a zpage so that dumping could be bounded, too. >Otherwise, it could encounter OOM easily. > >> compression factors better than 2:1? I have the impression (maybe >> wrong) that it does not. In our use of zram (Chrome OS) typical > >Since zswap changed allocator from zsmalloc to zbud, I didn't follow >because I had no interest of low compressoin ratio allocator so >I have no idea of status of zswap at a moment but I guess it would be >still 2:1. > >> overall compression ratios are between 2.5:1 and 3:1. We would hate >> to waste that memory if we switch to zswap. > >If you have real swap storage, zswap might be better although I have >no number but real swap is money for embedded system and it has sudden >garbage collection on firmware side if we use eMMC or SSD so that it >could affect system latency. Morever, if we start to use real swap, >maybe we should encrypt the data and it would be severe overhead(CPU >and Power). > Why real swap for embedded system need encrypt the data? I think there is no encrypt for data against server and desktop. >And what I am considering after promoting for zram feature is >asynchronous I/O and it's possible because zram is block device. > >Thanks! >-- >Kind regards, >Minchan Kim > >-- >To unsubscribe, send a message with 'unsubscribe linux-mm' in >the body to majordomo@kvack.org. For more info on Linux MM, >see: http://www.linux-mm.org/ . >Don't email: email@kvack.org -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org