Date: Wed, 22 Nov 2000 22:06:15 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: eischen@vigrid.com (Daniel Eischen) Cc: bright@wintelcom.net (Alfred Perlstein), jhb@FreeBSD.ORG (John Baldwin), jlemon@flugsvamp.com (Jonathan Lemon), arch@FreeBSD.ORG Subject: Re: Thread-specific data and KSEs Message-ID: <200011222206.PAA04455@usr07.primenet.com> In-Reply-To: <Pine.SUN.3.91.1001121221431.26351B-100000@pcnet1.pcnet.com> from "Daniel Eischen" at Nov 21, 2000 10:15:28 PM
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> > > >> %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
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