From owner-freebsd-stable@FreeBSD.ORG  Wed Jan 23 16:20:55 2013
Return-Path: <owner-freebsd-stable@FreeBSD.ORG>
Delivered-To: freebsd-stable@freebsd.org
Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115])
 by hub.freebsd.org (Postfix) with ESMTP id 30BB23E2;
 Wed, 23 Jan 2013 16:20:55 +0000 (UTC)
 (envelope-from adrian.chadd@gmail.com)
Received: from mail-wi0-f182.google.com (mail-wi0-f182.google.com
 [209.85.212.182])
 by mx1.freebsd.org (Postfix) with ESMTP id 4D08BE3F;
 Wed, 23 Jan 2013 16:20:54 +0000 (UTC)
Received: by mail-wi0-f182.google.com with SMTP id hn14so882459wib.15
 for <multiple recipients>; Wed, 23 Jan 2013 08:20:53 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113;
 h=mime-version:x-received:sender:in-reply-to:references:date
 :x-google-sender-auth:message-id:subject:from:to:cc:content-type;
 bh=BfXU5Wv8zGIoIcbRqpyfqjqu+JywYvrVillbCXrWakM=;
 b=GQKpRgIxjRsIy7CsjrDR4rW3l+/tNYOqYD9o8qLvERwVJz5ld4Mcx9DKMYqHx7UaAl
 /VUoveb2vV2vTpuAjqlzw1W93PaD7Y2CDZS1kqL4TBV5IxGBeU0tuxoFE6TBfjYlqHG/
 UMxY6kypfugRqy/qC8IeIX8N8yiLUXk/mT0GQsvtNyL5xKfYCR+fbnUHp/UZyHT74v+i
 CXEKV3ujx54bZWsSmCXvRUZTh0wfrW9+oary7OaNEsFSExqIgMldYankFuq2oL6qEoI4
 CTXNy81l57V842qdM4iFuhg4zWg8oCOzTpl+4SP9mE5yBD23Ui0CiuKd+iWmHX2YuD+m
 FmoQ==
MIME-Version: 1.0
X-Received: by 10.194.57.82 with SMTP id g18mr3717021wjq.25.1358958053226;
 Wed, 23 Jan 2013 08:20:53 -0800 (PST)
Sender: adrian.chadd@gmail.com
Received: by 10.216.67.6 with HTTP; Wed, 23 Jan 2013 08:20:52 -0800 (PST)
In-Reply-To: <50FFFA8B.4040008@FreeBSD.org>
References: <E1TxFcr-0006dx-MX@kabab.cs.huji.ac.il>
 <1358780588.32417.414.camel@revolution.hippie.lan>
 <E1TxJP2-000DS8-DJ@kabab.cs.huji.ac.il>
 <1358783667.32417.434.camel@revolution.hippie.lan>
 <CAJ-Vmo=2Dmf4Lb-uoUQDrybyRSS=_bnV5KcNYGg5MnMxfhhu7w@mail.gmail.com>
 <E1TxYHa-0002yo-4Y@kabab.cs.huji.ac.il>
 <CAJ-VmomdQORjs55ooW55Rgg0i1M13PPtnmCPRrp__btEWQz=4g@mail.gmail.com>
 <E1TxaZv-0005fj-5m@kabab.cs.huji.ac.il>
 <CAJ-VmokQbZFGmmy=KkEmP+7a6DQRGhdgupqF4sNCGJYxvA-B0g@mail.gmail.com>
 <50FFFA8B.4040008@FreeBSD.org>
Date: Wed, 23 Jan 2013 08:20:52 -0800
X-Google-Sender-Auth: H2DewRrq-2pH-iaBxfJ6QpDuKjc
Message-ID: <CAJ-Vmon7pT6=UJ5ppRO_3SWRw-QM9W2Bz1=ffq2ovjxHGyOUrA@mail.gmail.com>
Subject: Re: time issues and ZFS
From: Adrian Chadd <adrian@freebsd.org>
To: Andriy Gapon <avg@freebsd.org>
Content-Type: text/plain; charset=ISO-8859-1
Cc: freebsd-stable@freebsd.org, Ian Lepore <ian@freebsd.org>
X-BeenThere: freebsd-stable@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: Production branch of FreeBSD source code <freebsd-stable.freebsd.org>
List-Unsubscribe: <http://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: <http://lists.freebsd.org/mailman/listinfo/freebsd-stable>,
 <mailto:freebsd-stable-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 23 Jan 2013 16:20:55 -0000

On 23 January 2013 06:58, Andriy Gapon <avg@freebsd.org> wrote:

> I don't think that this is true of x86 hardware in general.
> You might have hit some limitation or a quirk or a bug or an erratum for some
> particular hardware.
>
> E.g. a chipset on this machine has a bit described as such:
> "Set to 1 to skip the C state transition if there is break event
> when entering C state."
> The bit is set indeed and as far as I can tell the behavior matches the description.
>
> Most modern (non-embedded) machines seem to behave this way. Attempt to enter a
> deeper C state while a break event is pending still incurs some overhead, but it's
> not as bad as waiting for the next break event.

I'll reverify the behaviour on my netbooks when I'm back home.

It may be a quirk of an older 9.x, which is fixed in -HEAD. It may be
a quirk of the older generation celeron hardware - in which case, we
need to tell the user somehow..



Adrian