From owner-freebsd-stable@FreeBSD.ORG  Fri May 12 21:14:19 2006
Return-Path: <owner-freebsd-stable@FreeBSD.ORG>
X-Original-To: stable@freebsd.org
Delivered-To: freebsd-stable@FreeBSD.ORG
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id D536E16AE94
	for <stable@freebsd.org>; Fri, 12 May 2006 21:14:19 +0000 (UTC)
	(envelope-from ivoras@fer.hr)
Received: from lara.cc.fer.hr (lara.cc.fer.hr [161.53.72.113])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 2113543D6A
	for <stable@freebsd.org>; Fri, 12 May 2006 21:13:58 +0000 (GMT)
	(envelope-from ivoras@fer.hr)
Received: from [127.0.0.1] (localhost.cc.fer.hr [127.0.0.1])
	by lara.cc.fer.hr (8.13.6/8.13.4) with ESMTP id k4CLDnYj087489
	for <stable@freebsd.org>; Fri, 12 May 2006 23:13:50 +0200 (CEST)
	(envelope-from ivoras@fer.hr)
Message-ID: <4464FA8D.5060309@fer.hr>
Date: Fri, 12 May 2006 23:13:49 +0200
From: Ivan Voras <ivoras@fer.hr>
User-Agent: Mozilla Thunderbird 1.0.6 (X11/20050921)
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: stable@freebsd.org
Content-Type: text/plain; charset=ISO-8859-2; format=flowed
Content-Transfer-Encoding: 7bit
Cc: 
Subject: pagezero again
X-BeenThere: freebsd-stable@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Production branch of FreeBSD source code <freebsd-stable.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/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: Fri, 12 May 2006 21:14:22 -0000

Some time ago I reported that pagezero kernel thread sometime takes 
(what seems to me) a too large chunk of available CPU (30%) on a very 
busy web server. There were no replies :( Since then, I've reconfigured 
apache to use PHP as a fastcgi module and the problem seems to have 
gotten worse - now it *always* takes ~25-30% CPU, and my "System" time 
stat shows it (its almost always ~30%).

 From what I can understand, pagezero thread fills kernel's pool of 
zeroed pages. This looks non-threteaning, but what would cause such high 
demand of zeroed pages on my system? The number of processes is almost 
constant, there are no frequent process spawnings or forks (top shows 
"last pid" to be almost constant). FastCGI processes communicate over 
UNIX sockets.

Also, pagezero thread is (should be) executing at idle priority - does 
this mean it won't interfere much with machine's performance? Even if 
"0% idle" is not uncommon state?

(This is FreeBSD 6.1-R, 2CPU SMP).