Date: Tue, 25 Apr 1995 18:23:41 -0700 (MST) From: Don Yuniskis <dgy@seagull.rtd.com> To: freebsd-hackers@freefall.cdrom.com (FreeBSD hackers) Subject: Re: benchmark hell.. (Really context switch & FPU) Message-ID: <199504260123.SAA20990@seagull.rtd.com> In-Reply-To: <199504260012.RAA09198@ref.tfs.com> from "Poul-Henning Kamp" at Apr 25, 95 05:12:30 pm
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> Well, you guys, when can we see the code ?? > > > I didn't explain. Sorry! I assumed we would want to do > > lazy FP context save/restore. Once you do that, further > > refinements don't buy you very much. If you reread what I > > wrote _in this context_, may be it will make more sense. > > > > > o The FPU has a "last used by" state variable > > > o When the first FPU using process is run, this variable is > > > set to its PID. > > Okay. I've implemented this in a couple of real-time OS's and it really is a big win -- especially if the FPU can execute in parallel with the CPU's execution unit (some FPU's can't) and you invest the time hooking the FPU traps to do belated switches *only on demand*. It does have some impact on real-time determinism ... but I doubt that would be a real issue in FBSD.
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