From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx114.postini.com [74.125.245.114]) by kanga.kvack.org (Postfix) with SMTP id 069976B0032 for ; Tue, 9 Jul 2013 20:31:43 -0400 (EDT) Date: Wed, 10 Jul 2013 09:31:42 +0900 From: Joonsoo Kim Subject: Re: [RFC PATCH 0/5] Support multiple pages allocation Message-ID: <20130710003142.GA2152@lge.com> References: <1372840460-5571-1-git-send-email-iamjoonsoo.kim@lge.com> <20130703152824.GB30267@dhcp22.suse.cz> <51D44890.4080003@gmail.com> <51D44AE7.1090701@gmail.com> <20130704042450.GA7132@lge.com> <20130704100044.GB7833@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130704100044.GB7833@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Zhang Yanfei , Andrew Morton , Mel Gorman , David Rientjes , Glauber Costa , Johannes Weiner , KOSAKI Motohiro , Rik van Riel , Hugh Dickins , Minchan Kim , Jiang Liu , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Thu, Jul 04, 2013 at 12:00:44PM +0200, Michal Hocko wrote: > On Thu 04-07-13 13:24:50, Joonsoo Kim wrote: > > On Thu, Jul 04, 2013 at 12:01:43AM +0800, Zhang Yanfei wrote: > > > On 07/03/2013 11:51 PM, Zhang Yanfei wrote: > > > > On 07/03/2013 11:28 PM, Michal Hocko wrote: > > > >> On Wed 03-07-13 17:34:15, Joonsoo Kim wrote: > > > >> [...] > > > >>> For one page allocation at once, this patchset makes allocator slower than > > > >>> before (-5%). > > > >> > > > >> Slowing down the most used path is a no-go. Where does this slow down > > > >> come from? > > > > > > > > I guess, it might be: for one page allocation at once, comparing to the original > > > > code, this patch adds two parameters nr_pages and pages and will do extra checks > > > > for the parameter nr_pages in the allocation path. > > > > > > > > > > If so, adding a separate path for the multiple allocations seems better. > > > > Hello, all. > > > > I modify the code for optimizing one page allocation via likely macro. > > I attach a new one at the end of this mail. > > > > In this case, performance degradation for one page allocation at once is -2.5%. > > I guess, remained overhead comes from two added parameters. > > Is it unreasonable cost to support this new feature? > > Which benchmark you are using for this testing? I use my own module which do allocation repeatedly. > > > I think that readahead path is one of the most used path, so this penalty looks > > endurable. And after supporting this feature, we can find more use cases. > > What about page faults? I would oppose that page faults are _much_ more > frequent than read ahead so you really cannot slow them down. You mean page faults for anon? Yes. I also think that it is much more frequent than read ahead. Before futher discussion, I will try to add a separate path for the multiple allocations. Thanks. > > [...] > -- > Michal Hocko > SUSE Labs > > -- > 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