From owner-cvs-src@FreeBSD.ORG  Tue Apr  6 20:43:18 2004
Return-Path: <owner-cvs-src@FreeBSD.ORG>
Delivered-To: cvs-src@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id 45FD616A4CE; Tue,  6 Apr 2004 20:43:18 -0700 (PDT)
Received: from mail.chesapeake.net (chesapeake.net [208.142.252.6])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id C93CF43D5A; Tue,  6 Apr 2004 20:43:17 -0700 (PDT)
	(envelope-from jroberson@chesapeake.net)
Received: from mail.chesapeake.net (localhost [127.0.0.1])
	by mail.chesapeake.net (8.12.10/8.12.10) with ESMTP id i373fHVf076717;
	Tue, 6 Apr 2004 23:41:17 -0400 (EDT)
	(envelope-from jroberson@chesapeake.net)
Received: from localhost (jroberson@localhost)i373fGAP076706;
	Tue, 6 Apr 2004 23:41:17 -0400 (EDT)
	(envelope-from jroberson@chesapeake.net)
X-Authentication-Warning: mail.chesapeake.net: jroberson owned process doing
	-bs
Date: Tue, 6 Apr 2004 23:41:15 -0400 (EDT)
From: Jeff Roberson <jroberson@chesapeake.net>
To: John Baldwin <jhb@FreeBSD.org>
In-Reply-To: <200404061912.i36JCP1m036228@repoman.freebsd.org>
Message-ID: <20040406234035.U72393@mail.chesapeake.net>
References: <200404061912.i36JCP1m036228@repoman.freebsd.org>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
cc: cvs-src@FreeBSD.org
cc: src-committers@FreeBSD.org
cc: cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/sys/conf options src/sys/kern kern_mutex.c
X-BeenThere: cvs-src@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: CVS commit messages for the src tree <cvs-src.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src>,
	<mailto:cvs-src-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/cvs-src>
List-Post: <mailto:cvs-src@freebsd.org>
List-Help: <mailto:cvs-src-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-src>,
	<mailto:cvs-src-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 07 Apr 2004 03:43:18 -0000

On Tue, 6 Apr 2004, John Baldwin wrote:

> jhb         2004/04/06 12:12:25 PDT
>
>   FreeBSD src repository
>
>   Modified files:
>     sys/conf             options
>     sys/kern             kern_mutex.c
>   Log:
>   Add a new kernel option MUTEX_WAKE_ALL that changes the mutex unlock code
>   to awaken all waiters when a contested mutex is released instead of just
>   the highest priority waiter.  If the various threads are awakened in
>   sequence then each thread may acquire and release the lock in question
>   without contention resulting in fewer expensive unlock and lock
>   operations.  This old behavior of waking just the highest priority is
>   still used if this option is specified.  Making the algorithm conditional
>   on a kernel option will allows us to benchmark both cases later and
>   determine which one should be used by default.

This seems like an optimization on UP and a pessimization on SMP.  Perhaps
you should make it conditional on mp_ncpus?

>
>   Requested by:   tanimura-san
>
>   Revision  Changes    Path
>   1.439     +1 -0      src/sys/conf/options
>   1.138     +10 -0     src/sys/kern/kern_mutex.c
>