Date: Mon, 20 Dec 1999 04:48:29 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Martin Cracauer <cracauer@cons.org> Cc: arch@freebsd.org Subject: Re: Concrete plans for ucontext/mcontext changes around 4.0 Message-ID: <Pine.BSF.4.10.9912200422230.8111-100000@alphplex.bde.org> In-Reply-To: <19991213091915.D13197@cons.org>
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On Mon, 13 Dec 1999, Martin Cracauer wrote: > First correction: > > > - Add one int member to use as 32 bitwise booleans to indicate what > > the SSE/additional space is used for in this signal invocation. FPU > > state will unconditionally be there. I think I prefer several u_int members giving the offset and size of each extension. > Forgot about lazy FPU context switching (should have finished reading > my mailbox). FPU context is not always there. > > The Linux people claim that lazy FPU switching is not worth the effort > anymore on modern machines. I didn't see any proof or numbers. Anyone > of you? fnsave+frstor takes about 213 cycles on a Celeron. Doing it unconditionally for every context switch would thus cost 250-500 nsec on a modern machine. This is probably still worth avoiding. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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