From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx135.postini.com [74.125.245.135]) by kanga.kvack.org (Postfix) with SMTP id 5FE236B0027 for ; Thu, 14 Mar 2013 19:42:03 -0400 (EDT) Received: from /spool/local by e28smtp05.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 15 Mar 2013 05:09:26 +0530 Received: from d28relay03.in.ibm.com (d28relay03.in.ibm.com [9.184.220.60]) by d28dlp02.in.ibm.com (Postfix) with ESMTP id E0E6C3940055 for ; Fri, 15 Mar 2013 05:11:55 +0530 (IST) Received: from d28av02.in.ibm.com (d28av02.in.ibm.com [9.184.220.64]) by d28relay03.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r2ENfoL99437586 for ; Fri, 15 Mar 2013 05:11:50 +0530 Received: from d28av02.in.ibm.com (loopback [127.0.0.1]) by d28av02.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id r2ENfrnB017833 for ; Fri, 15 Mar 2013 10:41:54 +1100 Date: Fri, 15 Mar 2013 07:41:52 +0800 From: Wanpeng Li Subject: Re: [PATCH 4/4] zcache: add pageframes count once compress zero-filled pages twice Message-ID: <20130314234152.GA1268@hacker.(null)> Reply-To: Wanpeng Li References: <1363158321-20790-1-git-send-email-liwanp@linux.vnet.ibm.com> <1363158321-20790-5-git-send-email-liwanp@linux.vnet.ibm.com> <634487ea-fbbd-4eb9-9a18-9206edc4e0d2@default> <20130314002056.GA10062@hacker.(null)> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Dan Magenheimer Cc: Greg Kroah-Hartman , Andrew Morton , Seth Jennings , Konrad Rzeszutek Wilk , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu, Mar 14, 2013 at 09:10:48AM -0700, Dan Magenheimer wrote: >> From: Wanpeng Li [mailto:liwanp@linux.vnet.ibm.com] >> Sent: Wednesday, March 13, 2013 6:21 PM >> To: Dan Magenheimer >> Cc: Andrew Morton; Greg Kroah-Hartman; Dan Magenheimer; Seth Jennings; Konrad Rzeszutek Wilk; Minchan >> Kim; linux-mm@kvack.org; linux-kernel@vger.kernel.org >> Subject: Re: [PATCH 4/4] zcache: add pageframes count once compress zero-filled pages twice >> >> On Wed, Mar 13, 2013 at 09:42:16AM -0700, Dan Magenheimer wrote: >> >> From: Wanpeng Li [mailto:liwanp@linux.vnet.ibm.com] >> >> Sent: Wednesday, March 13, 2013 1:05 AM >> >> To: Andrew Morton >> >> Cc: Greg Kroah-Hartman; Dan Magenheimer; Seth Jennings; Konrad Rzeszutek Wilk; Minchan Kim; linux- >> >> mm@kvack.org; linux-kernel@vger.kernel.org; Wanpeng Li >> >> Subject: [PATCH 4/4] zcache: add pageframes count once compress zero-filled pages twice >> > >> >Hi Wanpeng -- >> > >> >Thanks for taking on this task from the drivers/staging/zcache TODO list! >> > >> >> Since zbudpage consist of two zpages, two zero-filled pages compression >> >> contribute to one [eph|pers]pageframe count accumulated. >> > >> >> Hi Dan, >> >> >I'm not sure why this is necessary. The [eph|pers]pageframe count >> >is supposed to be counting actual pageframes used by zcache. Since >> >your patch eliminates the need to store zero pages, no pageframes >> >are needed at all to store zero pages, so it's not necessary >> >to increment zcache_[eph|pers]_pageframes when storing zero >> >pages. >> > >> >> Great point! It seems that we also don't need to caculate >> zcache_[eph|pers]_zpages for zero-filled pages. I will fix >> it in next version. :-) > >Hi Wanpeng -- > Hi Dan, >I think we DO need to increment/decrement zcache_[eph|pers]_zpages >for zero-filled pages. > >The main point of the counters for zpages and pageframes >is to be able to calculate density == zpages/pageframes. >A zero-filled page becomes a zpage that "compresses" to zero bytes >and, as a result, requires zero pageframes for storage. >So the zpages counter should be increased but the pageframes >counter should not. It is reasonable to me, I will increment/decrement zcache_[eph|pers]_zpages in next version. > >If you are changing the patch anyway, I do like better the use >of "zero_filled_page" rather than just "zero" or "zero page". >So it might be good to change: > >handle_zero_page -> handle_zero_filled_page >pages_zero -> zero_filled_pages >zcache_pages_zero -> zcache_zero_filled_pages > >and maybe > >page_zero_filled -> page_is_zero_filled Great rename! :-) Regards, Wanpeng Li > >Thanks, >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