From owner-freebsd-current@FreeBSD.ORG  Wed Apr  5 21:40:32 2006
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
X-Original-To: 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 D5EAB16A520;
	Wed,  5 Apr 2006 21:40:32 +0000 (UTC)
	(envelope-from julian@elischer.org)
Received: from a50.ironport.com (a50.ironport.com [63.251.108.112])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 500CD43D48;
	Wed,  5 Apr 2006 21:40:31 +0000 (GMT)
	(envelope-from julian@elischer.org)
Received: from unknown (HELO [10.251.17.229]) ([10.251.17.229])
	by a50.ironport.com with ESMTP; 05 Apr 2006 14:40:33 -0700
Message-ID: <4434394F.8020105@elischer.org>
Date: Wed, 05 Apr 2006 14:40:31 -0700
From: Julian Elischer <julian@elischer.org>
User-Agent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US;
	rv:1.7.11) Gecko/20050727
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: John Baldwin <jhb@freebsd.org>
References: <20060405003358.GA83600@tin.it>
	<200604051638.59800.jhb@freebsd.org>
In-Reply-To: <200604051638.59800.jhb@freebsd.org>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
Cc: Luigi Rizzo <rizzo@icir.org>, freebsd-current@freebsd.org
Subject: Re: Interesting data on network interrupt - part II
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: Wed, 05 Apr 2006 21:40:33 -0000

John Baldwin wrote:

>On Tuesday 04 April 2006 20:33, Paolo Pisati wrote:
>  
>
>>Hi, 
>>
>>i updated my work on interrupt profiling with sone new
>>experiments.
>>
>>In total we have now:
>>
>>-FreeBSD 4 PIC (no asm part)
>>-FreeBSD 7 APIC 
>>-FreeBSD 7 PIC
>>-FreeBSD 7 PREE APIC
>>-FreeBSD 7 APIC JHB
>>
>>Some quick comments:
>>
>>-PIC is much slower in masking interrupt (7k in PIC vs 3k in APIC)
>>-PREE let new thread save less than 500 ticks of 'queue' while 
>> preempted threads are often resumed after a lot
>>-JHB patch shaved 2.5k ticks in interrupt masking op
>>
>>For graphs, data and more comments:
>>
>>http://mercurio.sm.dsi.unimi.it/~pisati/interrupt/
>>    
>>
>
>I'll commit the patch then. :)  One thing you might try to do to better
>measure the effects of preemption is to generate kernel work so that
>the bge interrupts occur while the current thread is in the kernel
>rather than in userland.  In that case preemption should provide much
>lower latency for interrupt handlers, as w/o preemption, an interrupt
>in kernel mode won't run the ithread until either curthread blocks or
>returns to userland.
>  
>

it looks a bit like the preempted threads shuld be put onto a stack of 
threads to resume
so that when the pre-empter finishes, teh previosly active thread is 
resumed.
Basically, a preempted thread should be put at the HEAD of it's run 
queue, and not the tail..