From owner-freebsd-stable@FreeBSD.ORG  Thu Nov 22 20:25:17 2007
Return-Path: <owner-freebsd-stable@FreeBSD.ORG>
Delivered-To: freebsd-stable@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id DF02A16A46C;
	Thu, 22 Nov 2007 20:25:17 +0000 (UTC)
	(envelope-from kris@FreeBSD.org)
Received: from weak.local (pointyhat.freebsd.org [IPv6:2001:4f8:fff6::2b])
	by mx1.freebsd.org (Postfix) with ESMTP id B36A013C442;
	Thu, 22 Nov 2007 20:25:16 +0000 (UTC)
	(envelope-from kris@FreeBSD.org)
Message-ID: <4745E5B3.6060200@FreeBSD.org>
Date: Thu, 22 Nov 2007 21:25:23 +0100
From: Kris Kennaway <kris@FreeBSD.org>
User-Agent: Thunderbird 2.0.0.9 (Macintosh/20071031)
MIME-Version: 1.0
To: Alexey Popov <lol@chistydom.ru>
References: <4741905E.8050300@chistydom.ru>	<fhs3s5$knj$1@ger.gmane.org>	<47419AB3.5030008@chistydom.ru>	<fhs7hp$2es$2@ger.gmane.org>
	<4741A7DA.2050706@chistydom.ru> <4741DA15.9000308@FreeBSD.org>
	<47429DB8.7040504@chistydom.ru> <4742ADFE.40902@FreeBSD.org>
	<4742C46A.1060701@chistydom.ru> <47432F77.3030606@FreeBSD.org>
	<474339E9.4080301@FreeBSD.org> <4743629B.9090408@FreeBSD.org>
	<47456B71.5040205@chistydom.ru>
In-Reply-To: <47456B71.5040205@chistydom.ru>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
Cc: Attilio Rao <attilio@freebsd.org>, freebsd-stable@freebsd.org
Subject: Re: 2 x quad-core system is slower that 2 x dual core on FreeBSD
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: Thu, 22 Nov 2007 20:25:18 -0000

Alexey Popov wrote:
> Hi.
> 
> Kris Kennaway wrote:
>>>> In the meantime there is unfortunately not a lot that can be done, 
>>>> AFAICT.  There is one hack that I will send you later but it is not 
>>>> likely to help much.  I will also think about how to track down the 
>>>> cause of the contention further (the profiling trace only shows that 
>>>> it comes mostly from vget/vput but doesn't show where these are 
>>>> called from).
>>>
>>> Actually this patch might help.  It doesn't replace lockmgr but it 
>>> does fix a silly thundering herd behaviour.  It probably needs some 
>>> adjustment to get it to apply cleanly (it is about 7 months old), and 
>>> I apparently stopped using it because I ran into deadlocks.  It might 
>>> be stable enough to at least see how much it helps.
>> Try this one instead, it applies to HEAD.  You'll need to manually 
>> enter the paths though because of how p4 mangles diffs.
> Finally I tried your patch and it seems to help a little.
> 
> Now FreeBSD 7-STABLE ULE 8-core server without optimized PHP 
> realpath_cache_size (producing 2000+ lstats per request) can handle up 
> to ~24 rps as opposed to  max. 17 rps without your patch. %sys never 
> grows over %user with your patch. On the server with optimized 
> realpath_cache_size there's no visible influence of your patch.

You said "20" before for this configuration, so I'm a bit suspicious 
about how seriously to treat your measurements :)

Anyway, please obtain another lock profiling trace using the same 
conditions as the previous one (same workload & duration, etc), so we 
can compare what changed.

Kris