From owner-freebsd-arch Mon Nov 27 10:53:58 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 1277737B4E5 for ; Mon, 27 Nov 2000 10:53:45 -0800 (PST) Received: from laptop.baldwin.cx (john@jhb-laptop.osd.bsdi.com [204.216.28.241]) by pike.osd.bsdi.com (8.11.1/8.9.3) with ESMTP id eARIr3C40719; Mon, 27 Nov 2000 10:53:03 -0800 (PST) (envelope-from jhb@FreeBSD.org) 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: Date: Mon, 27 Nov 2000 10:53:16 -0800 (PST) From: John Baldwin To: Marius Bendiksen Subject: Re: Thread-specific data and KSEs Cc: arch@FreeBSD.org, Jonathan Lemon , Daniel Eischen , Alfred Perlstein Sender: owner-freebsd-arch@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On 27-Nov-00 Marius Bendiksen wrote: >> > 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? > > Upon loading a task state (with ltr or a gate), you will restore all > segment registers from the tss, regardless of their content, and a load of > the shadow portion of the segment will be attempted anyway. I don't think > this is the right place to shave off cycles, nor do I think the speed is > even the most relevant issue for this extension, but rather the abuse of > segments that are ment to hold real data. Erm, we don't use task gates or a TSS for our task switches. Go look at cpu_switch() in sys/i386/i386/swtch.s. %fs and %gs are intended to be used for per-CPU data and thread-local storage, which is why x86-64 keeps them around even after axeing %cs, %ds, %es, and %ss. > Marius -- 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