Date: Mon, 12 Jul 1999 10:50:45 +0200 (CEST) From: Oliver Fromme <olli@dorifer.heim3.tu-clausthal.de> To: freebsd-current@FreeBSD.ORG Subject: Re: "objtrm" problem probably found (was Re: Stuck in "objtrm") Message-ID: <199907120850.KAA21696@dorifer.heim3.tu-clausthal.de>
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Doug Rabson wrote in list.freebsd-current:
> On Mon, 12 Jul 1999, Peter Jeremy wrote:
> > That said, it should be fairly simple to change Matt's new in-line
> > assembler versions to insert LOCK prefixes when building an SMP
> > kernel. (Although I don't know that this is necessary yet, given
> > the `Big Giant Lock').
>
> We don't need the lock prefix for the current SMP implementation. A lock
> prefix would be needed in a multithreaded implementation but should not be
> added unless the kernel is an SMP kernel otherwise UP performance would
> suffer.
In my list of i386 clock cycles, the lock prefix is listed with
0 (zero) cycles. That would mean that it does not affect
performance on UP systems (except that it bloats the kernel by
1 byte for each such macro, which _might_ have negative effect
on the caches in the worst case, but this is not very likely).
Regards
Oliver
--
Oliver Fromme, Leibnizstr. 18/61, 38678 Clausthal, Germany
(Info: finger userinfo:olli@dorifer.heim3.tu-clausthal.de)
"In jedem Stück Kohle wartet ein Diamant auf seine Geburt"
(Terry Pratchett)
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