From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx152.postini.com [74.125.245.152]) by kanga.kvack.org (Postfix) with SMTP id 3700F6B00BA for ; Sat, 16 Feb 2013 20:52:24 -0500 (EST) Received: by mail-qa0-f51.google.com with SMTP id cr7so838711qab.10 for ; Sat, 16 Feb 2013 17:52:23 -0800 (PST) Message-ID: <512037D1.2010907@gmail.com> Date: Sun, 17 Feb 2013 09:52:17 +0800 From: Simon Jeons MIME-Version: 1.0 Subject: Re: zram /proc/swaps accounting weirdness References: <20121211062601.GD22698@blaptop> <9c96c9e7-4f6e-4e78-a207-009293c37b89@default> In-Reply-To: <9c96c9e7-4f6e-4e78-a207-009293c37b89@default> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Dan Magenheimer Cc: Minchan Kim , Nitin Gupta , Luigi Semenzato , linux-mm@kvack.org, Bob Liu On 12/12/2012 09:12 AM, Dan Magenheimer wrote: >> From: Dan Magenheimer >> Subject: RE: zram /proc/swaps accounting weirdness >> >>>> Can you explain how this could happen if num_writes never >>>> exceeded 1863? This may be harmless in the case where >>> Odd. >>> I tried to reproduce it with zram and real swap device without >>> zcache but failed. Does the problem happen only if enabling zcache >>> together? >> I also cannot reproduce it with only zram, without zcache. >> I can only reproduce with zcache+zram. Since zcache will >> only "fall through" to zram when the frontswap_store() call >> in swap_writepage() fails, I wonder if in both cases swap_writepage() >> is being called in large (e.g. SWAPFILE_CLUSTER-sized) blocks >> of pages? When zram-only, the entire block of pages always gets >> sent to zram, but with zcache only a small randomly-positioned >> fraction fail frontswap_store(), but the SWAPFILE_CLUSTER-sized >> blocks have already been pre-reserved on the swap device and >> become only partially-filled? > Urk. Never mind. My bad. When a swap page is compressed in > zcache, it gets accounted in the swap subsystem as an "inuse" Could you point out to me where add this count to swap subsystem? > page for the backing swap device. (Frontswap provides a > page-by-page "fronting store" for the swap device.) That explains > why Used is so high for the "zram swap device" even though > zram has only compressed a fraction of the pages... the > remaining (much larger) number of pages have been compressed > by/in zcache. > > Move along, there are no droids here. :-( > > Dan > > -- > 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