Date: Thu, 09 Jan 1997 16:11:03 +0100 From: Poul-Henning Kamp <phk@critter.dk.tfs.com> To: "Marc E. Fiuczynski" <mef@cs.washington.edu> Cc: smp@freebsd.org Subject: Re: unusual question Message-ID: <7514.852822663@critter.dk.tfs.com> In-Reply-To: Your message of "Wed, 08 Jan 1997 18:27:50 -0400." <32D41F66.3941@cs.washington.edu>
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>We are now interested to run SPIN on multiprocs using our FreeBSD 2.1.6
>driver base. I'm curious which device drivers are affected by the SMP
>code.
So far we have not modified any device-drivers for SMP operation.
This is only possible because we are still running in the OBULATEK mode
("One Big Ugly Lock Around The Entire Kernel").
>From prior experience, I would think that device drivers will be fitted
with a LOCK each, so that they stay unchanged, until such time as
somebody fits them with fine-grain locking.
Generally, you can allow device-drivers to be multi-threaded only as
far as you have separate pieces of hardware. Ie, in you average
FreeBSD system you could have one thread/cpu per sio port, but only
one for wdc0+wd0+wd1 because they share registers.
I would expect the "one-lock per device-driver" to be implemented
in the code that calls into the device drivers, simply to avoid
changing all of them, so most device-drivers will probably not
change much if at all.
--
Poul-Henning Kamp | phk@FreeBSD.ORG FreeBSD Core-team.
http://www.freebsd.org/~phk | phk@login.dknet.dk Private mailbox.
whois: [PHK] | phk@tfs.com TRW Financial Systems, Inc.
Power and ignorance is a disgusting cocktail.
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