Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932110AbbENGhB (ORCPT ); Thu, 14 May 2015 02:37:01 -0400 Received: from mail-la0-f46.google.com ([209.85.215.46]:36433 "EHLO mail-la0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751403AbbENGhA (ORCPT ); Thu, 14 May 2015 02:37:00 -0400 MIME-Version: 1.0 In-Reply-To: References: <1430732554-7294-1-git-send-email-jschoenh@amazon.de> <20150506082759.GA30019@gmail.com> <20150507102351.GA14347@gmail.com> Date: Thu, 14 May 2015 02:36:58 -0400 X-Google-Sender-Auth: 8ghHmzLDSqN3_ENyKNsVksiiFd0 Message-ID: Subject: Re: [PATCH] x86: skip delays during SMP initialization similar to Xen From: Len Brown To: Ingo Molnar Cc: =?UTF-8?Q?Jan_H=2E_Sch=C3=B6nherr?= , Thomas Gleixner , X86 ML , "linux-kernel@vger.kernel.org" , Anthony Liguori , Ingo Molnar , "H. Peter Anvin" , Tim Deegan , Gang Wei , Linus Torvalds Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1236 Lines: 32 > [ 0.404369] x86: Booting SMP configuration: ... > [ 2.737884] x86: Booted up 4 nodes, 120 CPUs > [ 2.743758] smpboot: Total of 120 processors activated (671097.18 BogoMIPS) > > (2.743758-0.404369) = 2.339389 for all 119 processors > /119 = .01965873109243697478 - lets call it 19ms each For the record, the same (bare metal) box running latest tip boots 10ms/processor quicker than upstream Linux, as expected. So this 120 processor box now boots 1.19 seconds faster, in total. [ 0.415969] x86: Booting SMP configuration: ... [ 1.553658] x86: Booted up 4 nodes, 120 CPUs [ 1.559173] smpboot: Total of 120 processors activated (671182.14 BogoMIPS) 1.553658-0.415969 = 1.137689 - seconds to bring 119 processors on-line. ./119 = .00956041176470588235 -- 9.5ms per processor, down from 19. BTW. this time can be reduced by 7% (113 ms) by deleting announce_cpu(): [ 1.445815] x86: Booted up 4 nodes, 120 CPUs cheers, Len Brown, Intel Open Source Technology Center -- 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/