From owner-freebsd-arch Tue Nov 21 20: 7:29 2000 Delivered-To: freebsd-arch@freebsd.org Received: from sharmas.dhs.org (c62443-a.frmt1.sfba.home.com [24.0.69.165]) by hub.freebsd.org (Postfix) with ESMTP id EC2FE37B479 for ; Tue, 21 Nov 2000 20:07:27 -0800 (PST) Received: (from adsharma@localhost) by sharmas.dhs.org (8.9.3/8.9.3) id UAA21967; Tue, 21 Nov 2000 20:05:41 -0800 Date: Tue, 21 Nov 2000 20:05:41 -0800 From: Arun Sharma To: Daniel Eischen Cc: arch@FreeBSD.ORG Subject: Re: Thread-specific data and KSEs Message-ID: <20001121200541.A21911@sharmas.dhs.org> References: <20001121192331.E18037@fw.wintelcom.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2i In-Reply-To: ; from eischen@vigrid.com on Tue, Nov 21, 2000 at 10:33:50PM -0500 Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Tue, Nov 21, 2000 at 10:33:50PM -0500, Daniel Eischen wrote: > On Tue, 21 Nov 2000, 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 according to swtch.s, it's just a movl instruction. I don't > need to use the segment register to address anything. I just > need to load it with a value (an index into a global array > of per-KSE structures). Loading a segment register on x86 results in privilege level checking. It may even generate a general protection fault. Section 4.6 of vol 3 (system programming guide) from Intel has more details. -Arun To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message