Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932620Ab3GOPQ0 (ORCPT ); Mon, 15 Jul 2013 11:16:26 -0400 Received: from relay2.sgi.com ([192.48.179.30]:47640 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932364Ab3GOPQZ (ORCPT ); Mon, 15 Jul 2013 11:16:25 -0400 Date: Mon, 15 Jul 2013 10:16:23 -0500 From: Robin Holt To: Ingo Molnar Cc: Robin Holt , Borislav Petkov , Robert Richter , "H. Peter Anvin" , Nate Zimmer , Linux Kernel , Linux MM , Rob Landley , Mike Travis , Daniel J Blueman , Andrew Morton , Greg KH , Yinghai Lu , Mel Gorman , Peter Zijlstra Subject: Re: [RFC 0/4] Transparent on-demand struct page initialization embedded in the buddy allocator Message-ID: <20130715151623.GB3421@sgi.com> References: <1373594635-131067-1-git-send-email-holt@sgi.com> <20130712082756.GA4328@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130712082756.GA4328@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: 1837 Lines: 46 On Fri, Jul 12, 2013 at 10:27:56AM +0200, Ingo Molnar wrote: > > * Robin Holt wrote: > > > [...] > > > > 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. > > That's pretty impressive. And WRONG! That is a 15x speedup in the freeing of memory at the free_all_bootmem point. That is _NOT_ the speedup from memmap_init_zone. I forgot to take that into account as Nate pointed out this morning in a hallway discussion. Before, on the 16TiB machine, memmap_init_zone took 1152 seconds. After, it took 50. If it were a straight 1/512th, we would have expected that 1152 to be something more on the line of 2-3 so there is still significant room for improvement. Sorry for the confusion. > It's still a 15x speedup instead of a 512x speedup, so I'd say there's > something else being the current bottleneck, besides page init > granularity. > > Can you boot with just a few gigs of RAM and stuff the rest into hotplug > memory, and then hot-add that memory? That would allow easy profiling of > remaining overhead. Nate and I will be working on other things for the next few hours hoping there is a better answer to the first question we asked about there being a way to test a page other than comparing against all zeroes to see if it has been initialized. Thanks, Robin -- 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/