From owner-freebsd-performance@FreeBSD.ORG  Tue Nov 23 02:34:59 2010
Return-Path: <owner-freebsd-performance@FreeBSD.ORG>
Delivered-To: freebsd-performance@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 0FD87106564A;
	Tue, 23 Nov 2010 02:34:59 +0000 (UTC)
	(envelope-from davidxu@freebsd.org)
Received: from freefall.freebsd.org (freefall.freebsd.org
	[IPv6:2001:4f8:fff6::28])
	by mx1.freebsd.org (Postfix) with ESMTP id F05E78FC15;
	Tue, 23 Nov 2010 02:34:58 +0000 (UTC)
Received: from xyf.my.dom (localhost [127.0.0.1])
	by freefall.freebsd.org (8.14.4/8.14.4) with ESMTP id oAN2YuJl018060;
	Tue, 23 Nov 2010 02:34:57 GMT (envelope-from davidxu@freebsd.org)
Message-ID: <4CEB98D6.40902@freebsd.org>
Date: Tue, 23 Nov 2010 10:35:02 +0000
From: David Xu <davidxu@freebsd.org>
User-Agent: Thunderbird 2.0.0.24 (X11/20100630)
MIME-Version: 1.0
To: Ivan Voras <ivoras@freebsd.org>
References: <iccd37$lhh$1@dough.gmane.org> <op.vmj44dm634t2sn@skeletor.lan>
	<4CEA9C46.8010507@freebsd.org> <icf1nk$192$1@dough.gmane.org>
	<icf36a$8ik$1@dough.gmane.org> <4CEB8AEF.7030202@freebsd.org>
	<AANLkTikyK_q1Uw+SWHB9EMTNRgiQhA9frhdUYy7KoQF_@mail.gmail.com>
In-Reply-To: <AANLkTikyK_q1Uw+SWHB9EMTNRgiQhA9frhdUYy7KoQF_@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Cc: freebsd-performance@freebsd.org
Subject: Re: PostgreSQL performance scaling
X-BeenThere: freebsd-performance@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Performance/tuning <freebsd-performance.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-performance>,
	<mailto:freebsd-performance-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-performance>
List-Post: <mailto:freebsd-performance@freebsd.org>
List-Help: <mailto:freebsd-performance-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-performance>,
	<mailto:freebsd-performance-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 23 Nov 2010 02:34:59 -0000

Ivan Voras wrote:
> On 23 November 2010 10:35, David Xu <davidxu@freebsd.org> wrote:
>> Ivan Voras wrote:
> 
>>> and the overall behaviour is similar - the processes spend a lot of time
>>> in "sbwait" and "ksem" states.
>>>
>> Strange, the POSIX semaphore in head branch does not use ksem, it is
>> based on umtx, there is no limit on POSIX semaphore, the only limit
>> is process's address space which limits how many semaphores can be
>> used.
> 
> *shrug*; I don't know how it could be wrong - this PostgreSQL was
> built from ports after I upgraded & booted 9-current.
> 
> If it didn't use POSIX semaphores from HEAD, shared semaphores
> wouldn't have worked, right?
> 

It may work, but even it is shared in memory, it still enters
kernel to do P/V operation.