Date: Wed, 22 Nov 2000 18:17:30 -0500 (EST) From: Daniel Eischen <eischen@vigrid.com> To: Terry Lambert <tlambert@primenet.com> Cc: Alfred Perlstein <bright@wintelcom.net>, John Baldwin <jhb@FreeBSD.ORG>, Jonathan Lemon <jlemon@flugsvamp.com>, arch@FreeBSD.ORG Subject: Re: Thread-specific data and KSEs Message-ID: <Pine.SUN.3.91.1001122180746.7920B-100000@pcnet1.pcnet.com> In-Reply-To: <200011222206.PAA04455@usr07.primenet.com>
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On Wed, 22 Nov 2000, Terry Lambert wrote: > > > > >> %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. Are WINE processes threaded? Do we really care? > 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. If you have an API in mind, send it to me. "current thread" is used an awful lot in the threads library and I'd like to avoid any uncessary levels of indirection, which is one reason I'd like to do it the way jhb suggested. -- Dan Eischen To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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