From owner-freebsd-current@FreeBSD.ORG  Thu Nov 24 00:10:23 2005
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
X-Original-To: current@FreeBSD.org
Delivered-To: freebsd-current@FreeBSD.ORG
Received: from [127.0.0.1] (localhost [127.0.0.1])
	by hub.freebsd.org (Postfix) with ESMTP id 5540816A41F;
	Thu, 24 Nov 2005 00:10:23 +0000 (GMT)
	(envelope-from davidxu@freebsd.org)
Message-ID: <43850500.5090908@freebsd.org>
Date: Thu, 24 Nov 2005 08:10:40 +0800
From: David Xu <davidxu@freebsd.org>
User-Agent: Mozilla/5.0 (X11; U; FreeBSD amd64; en-US;
	rv:1.7.10) Gecko/20050806
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: Kris Kennaway <kris@obsecurity.org>
References: <20051123201837.GA4822@xor.obsecurity.org>	<438500BE.3020507@freebsd.org>
	<20051123235741.GA10825@xor.obsecurity.org>
In-Reply-To: <20051123235741.GA10825@xor.obsecurity.org>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
Cc: current@FreeBSD.org
Subject: Re: 4BSD process starvation during I/O
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
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: Thu, 24 Nov 2005 00:10:24 -0000

Kris Kennaway wrote:

>On Thu, Nov 24, 2005 at 07:52:30AM +0800, David Xu wrote:
>  
>
>>Kris Kennaway wrote:
>>
>>    
>>
>>>Perhaps this can be tweaked.
>>>
>>>Kris
>>>
>>>P.S. Please, no responses about how maybe someone could write a new
>>>scheduler that doesn't have this property.
>>>
>>>
>>>
>>>
>>>      
>>>
>>Can you try it again with FULL_PREEMPTION is turned on ?
>>    
>>
>
>OK.  Is this option believed to be "safe" (i.e. largely free from
>bugs), and would it be useful to test more widely?
>
>Kris
>
>  
>
I didn't test it on big machine. if I remembered it correctly, we only
do preemption at user boundary if the FULL_PREEMPTION is turned off,
you know system thread won't go to user boundary. :-)

David Xu