From owner-freebsd-arch Wed Nov 22 14: 6:41 2000 Delivered-To: freebsd-arch@freebsd.org Received: from smtp04.primenet.com (smtp04.primenet.com [206.165.6.134]) by hub.freebsd.org (Postfix) with ESMTP id 1AB1E37B479; Wed, 22 Nov 2000 14:06:39 -0800 (PST) Received: (from daemon@localhost) by smtp04.primenet.com (8.9.3/8.9.3) id PAA23311; Wed, 22 Nov 2000 15:02:56 -0700 (MST) Received: from usr07.primenet.com(206.165.6.207) via SMTP by smtp04.primenet.com, id smtpdAAAnCaGrT; Wed Nov 22 15:02:45 2000 Received: (from tlambert@localhost) by usr07.primenet.com (8.8.5/8.8.5) id PAA04455; Wed, 22 Nov 2000 15:06:15 -0700 (MST) From: Terry Lambert Message-Id: <200011222206.PAA04455@usr07.primenet.com> Subject: Re: Thread-specific data and KSEs To: eischen@vigrid.com (Daniel Eischen) Date: Wed, 22 Nov 2000 22:06:15 +0000 (GMT) Cc: bright@wintelcom.net (Alfred Perlstein), jhb@FreeBSD.ORG (John Baldwin), jlemon@flugsvamp.com (Jonathan Lemon), arch@FreeBSD.ORG In-Reply-To: from "Daniel Eischen" at Nov 21, 2000 10:15:28 PM X-Mailer: ELM [version 2.5 PL2] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > > > >> %fs and %gs, but no other seg regs. > > > > > > > > All I need is one. > > > > > > Well, %gs would cover x86 and k64. I think ia64 has several > > > application registers that are available for OS use and we > > > could steal one of those. I'm not sure about the alpha though. > > > > Don't more segment registers cause more overhead for context switches? > > It's just one more register that has to be saved. I don't > think it's going to matter much. The %gs register already has to be saved for WINE processes, so it's taken (at least when USER_LDT is defined). So there would not be an additional context switch for it. I think that if you guys go forward with this, you should do an indirect through whatever you end up using. I realize this will cost an additional 6 clock cycles, but it will let you expand the list of things indefinitely, going forward, instead of having to keep a register dedicated for backward compatability, and then somehow "grow a new one" when you need to do something similar to this again, in the future. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message