From owner-freebsd-threads@FreeBSD.ORG  Wed Jun 18 01:56:21 2003
Return-Path: <owner-freebsd-threads@FreeBSD.ORG>
Delivered-To: freebsd-threads@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id AAEB337B401
	for <threads@freebsd.org>; Wed, 18 Jun 2003 01:56:21 -0700 (PDT)
Received: from bluejay.mail.pas.earthlink.net (bluejay.mail.pas.earthlink.net
	[207.217.120.218])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 197F143F75
	for <threads@freebsd.org>; Wed, 18 Jun 2003 01:56:21 -0700 (PDT)
	(envelope-from tlambert2@mindspring.com)
Received: from user-2ivfl1t.dialup.mindspring.com ([165.247.212.61]
	helo=mindspring.com)
	by bluejay.mail.pas.earthlink.net with asmtp (SSLv3:RC4-MD5:128)
	(Exim 3.33 #1)	id 19SYjc-0005CV-00; Wed, 18 Jun 2003 01:56:05 -0700
Message-ID: <3EF02888.4E72CE7F@mindspring.com>
Date: Wed, 18 Jun 2003 01:53:28 -0700
From: Terry Lambert <tlambert2@mindspring.com>
X-Mailer: Mozilla 4.79 [en] (Win98; U)
X-Accept-Language: en
MIME-Version: 1.0
To: David Xu <davidxu@viatech.com.cn>
References: <20030617071810.GA2451@dhcp01.pn.xcllnt.net><Pine.BSF.4.21.0306171433060.31025-100000@InterJet.elischer.org>
	<002101c3352a$e931a7f0$0701a8c0@tiger>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
X-ELNK-Trace: b1a02af9316fbb217a47c185c03b154d40683398e744b8a400d9487570c13715de391cab7bb4f1fc387f7b89c61deb1d350badd9bab72f9c350badd9bab72f9c
cc: threads@freebsd.org
cc: Julian Elischer <julian@elischer.org>
cc: Marcel Moolenaar <marcel@xcllnt.net>
Subject: Re: Nvidia, TLS and __thread keyword -- an observation
X-BeenThere: freebsd-threads@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Threading on FreeBSD <freebsd-threads.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-threads>,
	<mailto:freebsd-threads-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-threads>
List-Post: <mailto:freebsd-threads@freebsd.org>
List-Help: <mailto:freebsd-threads-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-threads>,
	<mailto:freebsd-threads-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 18 Jun 2003 08:56:22 -0000

David Xu wrote:
[ ... implicit TLS initialization and destruction ... ]

> I believe this will add overhead to thread creating and destroying,

Yes.  It will.  See my other posting for the tradeoffs.  The
complexity is not as bad as Marcel makes out, but it's still
a bad tradeoff for most existing threaded applications and
libraries, even if we thing more people will use implict TLS
as time goes on.

I think it's the wrong tradeoff, too.  I would make them burn
a general purpose register -- one that they are allowed to burn,
as an application -- on FreeBSD.  I have a hard time believing
that any of their functions use up all the registers, even on
a register-poor CISC architecture like x86; if they are that
complex, then they are doing so much stuff that explicit TLS
access overhead would be lost in the noise.

-- Terry