Date: Thu, 07 Dec 2000 19:32:55 -0800 From: Mike Smith <msmith@freebsd.org> To: Terry Lambert <tlambert@primenet.com> Cc: smp@FreeBSD.ORG Subject: Re: Netgraph and SMP Message-ID: <200012080332.eB83WtF00456@mass.osd.bsdi.com> In-Reply-To: Your message of "Fri, 08 Dec 2000 03:11:08 GMT." <200012080311.UAA02374@usr08.primenet.com>
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> In Solaris, the entry into the driver would hold a reference,
> which would result in the reference count being incremented.
> Only modules with a 0 reference count can be unloaded. This
> same mechanism is used for vnodes, and for modules on which
> other modules depend. It works well, ans is very light weight.
The whole problem is that it *isn't* very light weight.
The reference count has to be atomic, which means that it ping-pongs
around from CPU to CPU, causing a lot of extra cache traffic.
OTOH, there's not much we can do about this short of going looking for
better multi-CPU reference count implementations once we have time to
worry about performance.
--
... every activity meets with opposition, everyone who acts has his
rivals and unfortunately opponents also. But not because people want
to be opponents, rather because the tasks and relationships force
people to take different points of view. [Dr. Fritz Todt]
V I C T O R Y N O T V E N G E A N C E
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