[John R. Pierce]
> the catch is, that 2nd "CPU" is really only about 20% of one,
> but there's no
> real way the OS can know that.
Acutally, the OS *does* know, if it's a recent release.
Windows 2003, at least, favors the "first" virutal proccessor in a
multi-CPU, Hyperthreaded Xeon system. It distributes load across
physical processors first, utilizing the virtual hyperthreaded CPUs only
when each physical CPU is already running a at least one thread at 100%
capacity.
>From Intel's Hyperthreading whitepaper:
"Many of the
newer operating systems, either
released or soon to be released
(such as versions of Microsoft
Windows* .NET Server, certain
distribution versions of Linux, and
Novell NetWare), are expected to
include further optimizations for
Hyper-Threading technology.
These newer operating systems
can distinguish fully between
physical and logical processors,
allowing them to offer
improvements in scheduling and
idle loops in order to realize
optimal performance gains."
I recall reading somewhere that Windows XP SP1 and later also favor
physical processors first in a dual-Xeon system, but I cannot find that
reference.
Regards,
-Ryan-
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