Date: Wed, 22 Nov 2000 10:23:53 -0800 (PST) From: John Baldwin <jhb@FreeBSD.ORG> To: Alfred Perlstein <bright@wintelcom.net> Cc: arch@FreeBSD.ORG, Jonathan Lemon <jlemon@flugsvamp.com>, Daniel Eischen <eischen@vigrid.com> Subject: Re: Thread-specific data and KSEs Message-ID: <XFMail.001122102353.jhb@FreeBSD.org> In-Reply-To: <20001121175100.B18037@fw.wintelcom.net>
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On 22-Nov-00 Alfred Perlstein wrote: > * John Baldwin <jhb@FreeBSD.ORG> [001121 17:19] wrote: >> >> On 22-Nov-00 Daniel Eischen wrote: >> >> %gs ? as I mentioned in my other message, this one might be useful for >> >> addressing a structure of thread-local variables much like %fs is used >> >> for >> >> per-CPU data. It also has value in that supposedly x86-64 (aka k64) has >> >> both >> >> %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? Hardly. The biggest pain involved in a context switch is the TLB, not 2 (4?) extra mov instructions. :) > Just wondering. -- John Baldwin <jhb@FreeBSD.org> -- 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
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