From owner-freebsd-stable@freebsd.org  Thu Nov  3 04:09:46 2016
Return-Path: <owner-freebsd-stable@freebsd.org>
Delivered-To: freebsd-stable@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id 896C9C2CE23
 for <freebsd-stable@mailman.ysv.freebsd.org>;
 Thu,  3 Nov 2016 04:09:46 +0000 (UTC)
 (envelope-from smithi@nimnet.asn.au)
Received: from sola.nimnet.asn.au (paqi.nimnet.asn.au [115.70.110.159])
 (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id E6C8D1D8E
 for <freebsd-stable@freebsd.org>; Thu,  3 Nov 2016 04:09:44 +0000 (UTC)
 (envelope-from smithi@nimnet.asn.au)
Received: from localhost (localhost [127.0.0.1])
 by sola.nimnet.asn.au (8.14.2/8.14.2) with ESMTP id uA349WZl087611;
 Thu, 3 Nov 2016 15:09:33 +1100 (EST)
 (envelope-from smithi@nimnet.asn.au)
Date: Thu, 3 Nov 2016 15:09:32 +1100 (EST)
From: Ian Smith <smithi@nimnet.asn.au>
To: Konstantin Belousov <kostikbel@gmail.com>
cc: Jason Harmening <jason.harmening@gmail.com>, freebsd-stable@freebsd.org
Subject: Re: huge nanosleep variance on 11-stable
In-Reply-To: <20161102162808.GI54029@kib.kiev.ua>
Message-ID: <20161103150114.M41537@sola.nimnet.asn.au>
References: <c88341e2-4c52-ed3c-a469-6446da4415f4@gmail.com>
 <6167392c-c37a-6e39-aa22-ca45435d6088@gmail.com>
 <20161102075509.GF54029@kib.kiev.ua>
 <3620f62e-0f4c-2d62-dcf8-e2fdff459250@gmail.com>
 <20161102162808.GI54029@kib.kiev.ua>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
X-BeenThere: freebsd-stable@freebsd.org
X-Mailman-Version: 2.1.23
Precedence: list
List-Id: Production branch of FreeBSD source code <freebsd-stable.freebsd.org>
List-Unsubscribe: <https://lists.freebsd.org/mailman/options/freebsd-stable>, 
 <mailto:freebsd-stable-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-stable/>
List-Post: <mailto:freebsd-stable@freebsd.org>
List-Help: <mailto:freebsd-stable-request@freebsd.org?subject=help>
List-Subscribe: <https://lists.freebsd.org/mailman/listinfo/freebsd-stable>,
 <mailto:freebsd-stable-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 03 Nov 2016 04:09:46 -0000

On Wed, 2 Nov 2016 18:28:08 +0200, Konstantin Belousov wrote:
 > On Wed, Nov 02, 2016 at 09:18:15AM -0700, Jason Harmening wrote:
 > > I think you are probably right.  Hacking out the Intel-specific
 > > additions to C-state parsing in acpi_cpu_cx_cst() from r282678 (thus
 > > going back to sti;hlt instead of monitor+mwait at C1) fixed the problem
 > > for me.  But r282678 also had the effect of enabling C2 and C3 on my
 > > system, because ACPI only presents MWAIT entries for those states and
 > > not p_lvlx.

 > You can do the same with "debug.acpi.disabled=mwait" loader tunable
 > without hacking the code. And set sysctl hw.acpi.cpu.cx_lowest to C1 to
 > enforce use of hlt instruction even when mwait states were requested.

But hw.acpi.cpu.cx_lowest=C1 disables C2 & C3 etc, and Jason wanted 
those - but without using mwait - if I've read him right?

cheers, Ian