From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751159Ab3FWJc6 (ORCPT ); Sun, 23 Jun 2013 05:32:58 -0400 Received: from mail-ea0-f181.google.com ([209.85.215.181]:49412 "EHLO mail-ea0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750811Ab3FWJcz (ORCPT ); Sun, 23 Jun 2013 05:32:55 -0400 Date: Sun, 23 Jun 2013 11:32:50 +0200 From: Ingo Molnar To: Nathan Zimmer Cc: holt@sgi.com, travis@sgi.com, rob@landley.net, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.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 Message-ID: <20130623093250.GA13776@gmail.com> References: <1371831934-156971-1-git-send-email-nzimmer@sgi.com> <1371831934-156971-3-git-send-email-nzimmer@sgi.com> <20130623092840.GB13445@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130623092840.GB13445@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * 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. Thanks, Ingo