Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753416Ab3GQJaz (ORCPT ); Wed, 17 Jul 2013 05:30:55 -0400 Received: from relay3.sgi.com ([192.48.152.1]:36061 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752431Ab3GQJay (ORCPT ); Wed, 17 Jul 2013 05:30:54 -0400 Date: Wed, 17 Jul 2013 04:30:52 -0500 From: Robin Holt To: Sam Ben Cc: Robin Holt , "H. Peter Anvin" , Ingo Molnar , Nate Zimmer , Linux Kernel , Linux MM , Rob Landley , Mike Travis , Daniel J Blueman , Andrew Morton , Greg KH , Yinghai Lu , Mel Gorman Subject: Re: [RFC 0/4] Transparent on-demand struct page initialization embedded in the buddy allocator Message-ID: <20130717093051.GK3421@sgi.com> References: <1373594635-131067-1-git-send-email-holt@sgi.com> <51E628F8.6030303@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51E628F8.6030303@gmail.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3123 Lines: 66 On Wed, Jul 17, 2013 at 01:17:44PM +0800, Sam Ben wrote: > On 07/12/2013 10:03 AM, Robin Holt wrote: > >We have been working on this since we returned from shutdown and have > >something to discuss now. We restricted ourselves to 2MiB initialization > >to keep the patch set a little smaller and more clear. > > > >First, I think I want to propose getting rid of the page flag. If I knew > >of a concrete way to determine that the page has not been initialized, > >this patch series would look different. If there is no definitive > >way to determine that the struct page has been initialized aside from > >checking the entire page struct is zero, then I think I would suggest > >we change the page flag to indicate the page has been initialized. > > > >The heart of the problem as I see it comes from expand(). We nearly > >always see a first reference to a struct page which is in the middle > >of the 2MiB region. Due to that access, the unlikely() check that was > >originally proposed really ends up referencing a different page entirely. > >We actually did not introduce an unlikely and refactor the patches to > >make that unlikely inside a static inline function. Also, given the > >strong warning at the head of expand(), we did not feel experienced > >enough to refactor it to make things always reference the 2MiB page > >first. > > > >With this patch, we did boot a 16TiB machine. Without the patches, > >the v3.10 kernel with the same configuration took 407 seconds for > >free_all_bootmem. With the patches and operating on 2MiB pages instead > >of 1GiB, it took 26 seconds so performance was improved. I have no feel > >for how the 1GiB chunk size will perform. > > How to test how much time spend on free_all_bootmem? We had put a pr_emerg at the beginning and end of free_all_bootmem and then used a modified version of script which record the time in uSecs at the beginning of each line of output. Robin > > > > >I am on vacation for the next three days so I am sorry in advance for > >my infrequent or non-existant responses. > > > > > >Signed-off-by: Robin Holt > >Signed-off-by: Nate Zimmer > >To: "H. Peter Anvin" > >To: Ingo Molnar > >Cc: Linux Kernel > >Cc: Linux MM > >Cc: Rob Landley > >Cc: Mike Travis > >Cc: Daniel J Blueman > >Cc: Andrew Morton > >Cc: Greg KH > >Cc: Yinghai Lu > >Cc: Mel Gorman > >-- > >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/ -- 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/