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SubjectRe: Very high load on P4 machines with 2.4.28
On Tue, 4 Jan 2005, Nicholas Berry wrote:

> >>> Willy Tarreau <willy@w.ods.org> 01/04/05 5:05 PM >>>
> >> Oh, while I'm at it, are you using hyperthreading, and if so, could
> you
> >> disable it ? I have seen many cases where it degrades performances
> >> significantly (eg: highly loaded user space network applications).
>
> >Willy
>
> Indeed. AIX (sorry) 5.3 on POWER5 explicitly disables SMT (IBM
> hyperthreading) if the load doesn't warrant it.
>
Heh, yeah, that's pretty funky. I was initially pretty baffled first time
topas on a AIX 5.3 box showed me I had 6 CPU's but quitting it and
starting it 2sec later showed me 8 CPU's (box has 4 physical CPUs). That
send me hunting through docs. On the surface it seems like a nice feature,
but if it makes any real difference or not I've had difficulty in
determining.

--
Jesper Juhl

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