From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752530Ab3FXRie (ORCPT ); Mon, 24 Jun 2013 13:38:34 -0400 Received: from terminus.zytor.com ([198.137.202.10]:58213 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751444Ab3FXRid (ORCPT ); Mon, 24 Jun 2013 13:38:33 -0400 Message-ID: <51C88400.7090907@zytor.com> Date: Mon, 24 Jun 2013 10:38:08 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 MIME-Version: 1.0 To: Ingo Molnar CC: Nathan Zimmer , holt@sgi.com, travis@sgi.com, rob@landley.net, tglx@linutronix.de, mingo@redhat.com, yinghai@kernel.org, akpm@linux-foundation.org, gregkh@linuxfoundation.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds , Peter Zijlstra Subject: Re: [RFC 2/2] x86_64, mm: Reinsert the absent memory References: <1371831934-156971-1-git-send-email-nzimmer@sgi.com> <1371831934-156971-3-git-send-email-nzimmer@sgi.com> <20130623092840.GB13445@gmail.com> <20130623093250.GA13776@gmail.com> In-Reply-To: <20130623093250.GA13776@gmail.com> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/23/2013 02:32 AM, Ingo Molnar wrote: > > * Ingo Molnar wrote: > >> Yet another thing to consider would be to implement an initialization >> speedup of 3 orders of magnitude: initialize on the large page (2MB) >> grandularity and on-demand delay the initialization of the 4K granular >> struct pages [but still allocating them] - which I suspect are a good >> chunk of the overhead? That way we could initialize in 2MB steps and speed >> up the 2 hours bootup of 32 TB of RAM to 14 seconds... >> >> [ The cost would be one more branch in the buddy allocator, to detect >> not-yet-initialized 2 MB chunks as we encounter them. Acceptable I >> think. ] > > One advantage of this scheme would be that we could use it on pretty much > any box, it would provide instant boot time speedups everywhere [a couple > of hundred msecs on a small 4GB box - significant I think] - and would > spread out and parallelize initialization to later stages. > Even better if we could start at the 1 GB level, which most of these really huge machines will have hardware support for. -hpa