On Fri, Jan 31, 2003 at 11:08:38AM -0800, Matthew Dillon wrote:
>
> :AFAIK, full hyperthreading support, as it is, has been merged to
> :-stable. It consists of a patch to recognize the virtual CPUs, so they
> :will be dealt with like any SMP system, as long as HTT is enabled on the
> :BIOS.
> :
> :--
> :Daniel C. Sobral (8-DCS)
> :Gerencia de Operacoes
>
> Yah. Shoot, well this Sony VAIO desktop has a P4 with HTT set in
> it, but it doesn't have an APIC, the BIOS is clueless, and there
> is no mptable, so I guess I am S.O.L. in regards to using hyperthreading
> on this box.
>
> -Matt
> Matthew Dillon
> <dillon@backplane.com>
Why do you think that hlt-ing the CPU(s) when idle would actually
improve performance in this case? My only suspicion is that perhaps
this reduces scheduling on the auxiliary 'logical' (fake) CPUs,
thereby indirectly reducing cache ping-ponging and abuse. I would
imagine that both units sharing the same execution engine in the
HTT-enabled model would be effectively 'hlt'-ed when one of the two
threads executes an 'hlt' until the next timer tick.
I guess we'll wait for the two other data sets from Trish: one with
HTT off, and cpu_idle_hlt=0, and the other with HTT off, and
cpu_idle_hlt=1, before figuring this out.
--
Bosko Milekic * bmilekic@unixdaemons.com * bmilekic@FreeBSD.org
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