From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1755648AbbE2IFH (ORCPT <rfc822;w@1wt.eu>);
	Fri, 29 May 2015 04:05:07 -0400
Received: from smtp-fw-4101.amazon.com ([72.21.198.25]:61945 "EHLO
	smtp-fw-4101.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1755628AbbE2IEx (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Fri, 29 May 2015 04:04:53 -0400
X-IronPort-AV: E=Sophos;i="5.13,515,1427760000"; 
   d="scan'208";a="276371152"
Message-ID: <55681D9B.2040903@amazon.de>
Date: Fri, 29 May 2015 10:04:43 +0200
From: =?UTF-8?B?IkphbiBILiBTY2jDtm5oZXJyIg==?= <jschoenh@amazon.de>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0
MIME-Version: 1.0
To: Len Brown <lenb@kernel.org>, Ingo Molnar <mingo@kernel.org>
CC: Thomas Gleixner <tglx@linutronix.de>, X86 ML <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Anthony Liguori <aliguori@amazon.com>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Tim Deegan <tim@xen.org>,
        Gang Wei <gang.wei@intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: native_cpu_up speed (Re: [PATCH] x86: skip delays during SMP
 initialization similar to Xen)
References: <CAJvTdKmz9105cYDiZThfCd29PWeNh2d2QbZFZ0n_UEeqCah7Fg@mail.gmail.com>
In-Reply-To: <CAJvTdKmz9105cYDiZThfCd29PWeNh2d2QbZFZ0n_UEeqCah7Fg@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 05/29/2015 09:47 AM, Len Brown wrote:
> However, a clear pattern jumped out of the trace for how long
> the BSP waits for the AP to set itself in cpu_callin_mask.
> This is the time in start secondary where cpu_init() is running,
> up through smp_callin() is called.
>
> On the 1st package, each remote AP take 9 delays = 900 us to do this,
> whether they are new cores or HT siblings of cores already up.
> But the 1st processor on remote_packages_  aka nodes, takes 60,000 us
>
> No typo -- that is 60ms!

That does sound like calibrate_delay(), which "waits" for 5 * (10ms + 1 tick)
on each newly encountered package...

Regards
Jan