From owner-freebsd-current@FreeBSD.ORG  Tue Jul 20 14:33:46 2004
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id 3B4F316A4CF; Tue, 20 Jul 2004 14:33:46 +0000 (GMT)
Received: from storm.FreeBSD.org.uk (storm.FreeBSD.org.uk [194.242.157.42])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id B1AEE43D48; Tue, 20 Jul 2004 14:33:45 +0000 (GMT)
	(envelope-from mark@grondar.org)
Received: from storm.FreeBSD.org.uk (Ugrondar@localhost [127.0.0.1])
	i6KEXisd021058;	Tue, 20 Jul 2004 15:33:44 +0100 (BST)
	(envelope-from mark@grondar.org)
Received: (from Ugrondar@localhost)i6KEXiO8021057;
	Tue, 20 Jul 2004 15:33:44 +0100 (BST)
	(envelope-from mark@grondar.org)
X-Authentication-Warning: storm.FreeBSD.org.uk: Ugrondar set sender to
	mark@grondar.org using -f
Received: from grondar.org (localhost [127.0.0.1])i6KEJxJX079041;
	Tue, 20 Jul 2004 15:19:59 +0100 (BST)
	(envelope-from mark@grondar.org)
Message-Id: <200407201419.i6KEJxJX079041@grimreaper.grondar.org>
To: Robert Watson <rwatson@FreeBSD.ORG>
From: Mark Murray <markm@FreeBSD.ORG>
In-Reply-To: Your message of "Tue, 20 Jul 2004 09:32:08 EDT."
             <Pine.NEB.3.96L.1040720093036.86342D-100000@fledge.watson.org> 
Date: Tue, 20 Jul 2004 15:19:59 +0100
Sender: mark@grondar.org
cc: jesk <jesk@killall.org>
cc: freebsd-current@FreeBSD.ORG
Subject: Re: I/O or Threading Suffer 
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 20 Jul 2004 14:33:46 -0000

Robert Watson writes:
> On Tue, 20 Jul 2004, Scott Long wrote:
> 
> > If you are dd'ing from /dev/random, then you are depleting the entropy
> > pool.  Anything else that tries to get random numbers is going to block
> > in strange ways.  Trying just dd'ing from /dev/zero and see if that
> > makes a difference. 
> 
> With Yarrow, /dev/random should just keep on chugging, so this is unlikely
> to be the source.  However, lots of /dev/random I/O may take a while to
> yield if it's working hard in kernel, so if that is combined with a
> scheduling nit of some sort, we could be looking at a starvation issue.

When you read /dev/random, you only exercise the output generator, and this
is a pretty simple piece of code.

Yarrow's kernel thread is used ONLY for the entropy harvesting, and is only
indirectly coupled to the output generator.

M
--
Mark Murray
iumop ap!sdn w,I idlaH