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Re: FPU emulator unsafe for SMP?

To: Greg Lindahl <lindahl@conservativecomputer.com>
Subject: Re: FPU emulator unsafe for SMP?
From: Ralf Baechle <ralf@oss.sgi.com>
Date: Wed, 20 Feb 2002 14:10:51 +0100
Cc: linux-mips@oss.sgi.com
In-reply-to: <20020219222835.A4195@wumpus.skymv.com>; from lindahl@conservativecomputer.com on Tue, Feb 19, 2002 at 10:28:35PM -0500
References: <3C6C6ACF.CAD2FFC@mvista.com> <20020215031118.B21011@dea.linux-mips.net> <20020214232030.A3601@mvista.com> <20020215003037.A3670@mvista.com> <002b01c1b607$6afbd5c0$10eca8c0@grendel> <20020219140514.C25739@mvista.com> <00af01c1b9a2$c0d6d5f0$10eca8c0@grendel> <20020219171238.E25739@mvista.com> <20020219222835.A4195@wumpus.skymv.com>
Sender: owner-linux-mips@oss.sgi.com
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On Tue, Feb 19, 2002 at 10:28:35PM -0500, Greg Lindahl wrote:

> What you propose, locking the fpu owner to the current cpu, will not
> result in a fair solution. Imagine a 2 cpu machine with 2 processes
> using integer math and 1 using floating point... how much cpu time
> will each process get? Imagine all the funky effects. Now add in a
> MIPS design in which interrupts are not delivered uniformly to all the
> cpus... I don't know if there are any or will ever be any, but...

They already exist, SGI Origin.

  Ralf

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