From owner-cvs-all@FreeBSD.ORG  Thu Apr  3 09:55:46 2003
Return-Path: <owner-cvs-all@FreeBSD.ORG>
Delivered-To: cvs-all@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 73D3E37B401
	for <cvs-all@FreeBSD.org>; Thu,  3 Apr 2003 09:55:46 -0800 (PST)
Received: from rootlabs.com (root.org [67.118.192.226])
	by mx1.FreeBSD.org (Postfix) with SMTP id 46B9443FBD
	for <cvs-all@FreeBSD.org>; Thu,  3 Apr 2003 09:55:45 -0800 (PST)
	(envelope-from nate@rootlabs.com)
Received: (qmail 14543 invoked by uid 1000); 3 Apr 2003 17:55:46 -0000
Date: Thu, 3 Apr 2003 09:55:45 -0800 (PST)
From: Nate Lawson <nate@root.org>
To: Peter Wemm <peter@wemm.org>
In-Reply-To: <20030403012341.B55B32A8A7@canning.wemm.org>
Message-ID: <Pine.BSF.4.21.0304030952381.14522-100000@root.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.i386 src/sys/i386/i386machdep.c
 mp_machdep.c pmap.c swtch.s src/sys/i386/include md_var.h pmap.h smp.h
 src/sys/i386/isa apic_vector.s intr_machdep.h src/sys/kern kern_switch.c
 kern_synch.c kern_thr.c kern_thread.c subr_witness.c ... 
X-BeenThere: cvs-all@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: CVS commit messages for the entire tree <cvs-all.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-all>,
	<mailto:cvs-all-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/cvs-all>
List-Post: <mailto:cvs-all@freebsd.org>
List-Help: <mailto:cvs-all-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/cvs-all>,
	<mailto:cvs-all-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 03 Apr 2003 17:55:47 -0000

On Wed, 2 Apr 2003, Peter Wemm wrote:
> Nate Lawson wrote:
> > Shouldn't there be a "if (thread == curthread) return;" in the scheduling
> > code somewhere?
> 
> There is now. :-)
> 
>         newtd = choosethread();
>         if (td != newtd)
>                 cpu_switch(td, newtd);  /* SHAZAM!! */
> #ifdef SWTCH_OPTIM_STATS
>         else
>                 stupid_switch++;
> #endif
> 
> sparc64's cpu_switch() already optimized this case.  i386 didn't.  I haven't
> checked alpha/ia64 yet, but they're still using the old no-args API.

The more things change...

"Probably 30% of the performance improvements came from fixing things in
the Sun kernel.  I mean like, really, guys:  If the current task doesn't
change, and it doesn't 80% of the time swtch is called, there's no need
to do a full context save and restore.  Adding the two lines

    cmpl    _masterprocp,a0
    jeq     6f               restore of current proc is easy

just before the call to "resume" in sun3/vax.s:swtch got me a quick 70
KB/s performance increase but felt more like a bug fix than progress."
   -- van

http://www.root.org/ip-development/news/vanj.88jul20.txt

-Nate