From owner-freebsd-arch Wed Nov 22 10:31:46 2000 Delivered-To: freebsd-arch@freebsd.org Received: from pike.osd.bsdi.com (pike.osd.bsdi.com [204.216.28.222]) by hub.freebsd.org (Postfix) with ESMTP id 4AE2A37B4C5 for ; Wed, 22 Nov 2000 10:31:44 -0800 (PST) Received: from foo.osd.bsdi.com (root@foo.osd.bsdi.com [204.216.28.137]) by pike.osd.bsdi.com (8.11.0/8.9.3) with ESMTP id eAMIVT041749; Wed, 22 Nov 2000 10:31:29 -0800 (PST) (envelope-from jhb@foo.osd.bsdi.com) Received: (from jhb@localhost) by foo.osd.bsdi.com (8.11.1/8.11.0) id eAMIRcg55300; Wed, 22 Nov 2000 10:27:38 -0800 (PST) (envelope-from jhb) Message-ID: X-Mailer: XFMail 1.4.0 on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: <20001121192331.E18037@fw.wintelcom.net> Date: Wed, 22 Nov 2000 10:27:38 -0800 (PST) Organization: BSD, Inc. From: John Baldwin To: Alfred Perlstein Subject: Re: Thread-specific data and KSEs Cc: arch@FreeBSD.ORG, Jonathan Lemon , Daniel Eischen Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On 22-Nov-00 Alfred Perlstein wrote: > * Daniel Eischen [001121 19:15] wrote: >> > >> > 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. > > No extra TLB faults/invalidations? Aren't segment registers > somewhat expensive to load? Not really. The TLB stuff happens when you change %cr3. Also, if you look in cpu_switch, we already save and restore %gs. :) (Which means it may already be used. :( ) Some extra overhead may come from changing the ldt, although if you stick USER_LDT in your kernel you already do that anyways. -- John Baldwin -- http://www.FreeBSD.org/~jhb/ PGP Key: http://www.Baldwin.cx/~john/pgpkey.asc "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message