Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751232Ab3HPEgN (ORCPT ); Fri, 16 Aug 2013 00:36:13 -0400 Received: from mail-ie0-f179.google.com ([209.85.223.179]:45559 "EHLO mail-ie0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750902Ab3HPEgK (ORCPT ); Fri, 16 Aug 2013 00:36:10 -0400 Date: Fri, 16 Aug 2013 13:35:56 +0900 From: Minchan Kim To: Wanpeng Li 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 Subject: Re: [PATCH v6 0/5] zram/zsmalloc promotion Message-ID: <20130816043556.GA6216@gmail.com> References: <1376459736-7384-1-git-send-email-minchan@kernel.org> <20130814161753.GB2706@gmail.com> <520d883a.a2f6420a.6f36.0d66SMTPIN_ADDED_BROKEN@mx.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <520d883a.a2f6420a.6f36.0d66SMTPIN_ADDED_BROKEN@mx.google.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2754 Lines: 70 Hi, On Fri, Aug 16, 2013 at 10:02:08AM +0800, Wanpeng Li wrote: > 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. I have used some portable device but suddenly, I lost it or was stolen. A hacker can pick it up and read my swap and found my precious information. I don't want it. I guess it's one of reason ChromeOS don't want to use real swap. https://groups.google.com/a/chromium.org/forum/#!msg/chromium-os-discuss/92Fvi4Ezego/ZvbrC3L2FG4J > > >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 > -- Kind regards, Minchan Kim -- 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/