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Date:      Mon, 15 Jan 2001 14:38:21 -0700
From:      "Justin T. Gibbs" <gibbs@scsiguy.com>
To:        John Baldwin <jhb@FreeBSD.org>
Cc:        Bruce Evans <bde@zeta.org.au>, cvs-all@FreeBSD.org, cvs-committers@FreeBSD.org, Wilko Bulte <wkb@freebie.demon.nl>, Poul-Henning Kamp <phk@critter.freebsd.dk>, Peter Wemm <peter@netplex.com.au>
Subject:   Re: cvs commit: src/sys/i386/conf GENERIC 
Message-ID:  <200101152138.f0FLcLs61722@aslan.scsiguy.com>
In-Reply-To: Your message of "Mon, 15 Jan 2001 13:34:34 PST." <XFMail.010115133434.jhb@FreeBSD.org> 

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>> All that is required in the userland implementation is the setting of a
>> flag so the userland thread scheduler does not perform a thread switch.
>> Having an interrupt fire does not have the same consequences on a userland
>> program as it does for the kernel.
>
>Actually, the process needs to not be switched.  This is part of KSE, so you
>would have to set a kernel flag in the kse for this, but yes, that would work.
> 
>Granted, it pessimizes the non-i386 case, but not that badly.  The kernel trap
>to emulate only pessimizes the i386 case (though the 386 could do without extr
>a pessimizations, and it is a bigger pessimization.)

I suppose I haven't read enough of the KSE stuff to understand why
you need to not change processes (or is a process the "unit" used
to represent a KSE?).  Doesn't the userland scheduler decide what
to do with any KSE it is given?

Anyway, if you use the "patch up the atomic operation" approach, you
don't pessimize anyone except on the first run through a particular
atomic operation.

--
Justin


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