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Date:      Wed, 01 Dec 1999 17:42:44 -0500
From:      "Daniel M. Eischen" <eischen@vigrid.com>
To:        Wes Peters <wes@softweyr.com>
Cc:        "Richard Seaman, Jr." <dick@tar.com>, arch@freebsd.org
Subject:   Re: Threads stuff
Message-ID:  <3845A464.6CA5B28A@vigrid.com>
References:  <Pine.BSF.4.10.9911282113490.544-100000@current1.whistle.com> <384270AE.D0250340@vigrid.com> <38440BAB.E547CA61@vigrid.com> <19991130122423.N29767@tar.com> <38459FEF.B04F4617@softweyr.com>

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Wes Peters wrote:
> 
> "Richard Seaman, Jr." wrote:
> >
> > On Tue, Nov 30, 1999 at 12:38:51PM -0500, Daniel M. Eischen wrote:
> >
> > > I think we can perform thread switches totally in
> > > userland without any assistance from the kernel.
> >
> > This would be a big performance plus.
> 
> Not if you want those threads to run on multiple processors in an SMP box.

Each cooperating subprocess has an upcall context and can perform
switches for threads within the subprocess.  So if you have multiple
subprocesses and multiple CPUs, then you can have simultaneous
thread switches occuring on each CPU.

That's for async call-gates/SAs.  Under Matts proposal, you don't need
multiple subprocesses (rforks) in order to run simultaneously on multiple
CPUs.

Dan Eischen
eischen@vigrid.com




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