Bugs item #673085, was opened at 2003-01-23 06:12
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: Hyperthreaded CPU count is wrong
Initial Comment:
Ganglia reports the 4 virtual processors as the number
of CPUs on
a dual physical CPU machine. This gives the false
impression of the
system being half loaded when in fact it's fully loaded.
Since hyperthreading is new and people will most likely
want different
behaviours, perhaps the best solution is to offer a
configuration option
to count virtual or physical CPUs when reporting such info.
By the way, with the latest RedHat kernel
(2.4.18-19.7.x), you can
correctly determine the number of physical CPUs (via
command line)
by:
$ grep "Physical processor" /proc/cpuinfo | uniq | wc -l
2
Thanks,
-Tim Miller
millerte @ wfu - edu
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>Comment By: Federico David Sacerdoti (sacerdoti)
Date: 2003-01-23 12:59
Message:
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I would argue that ganglia should report the same number of CPUs as
the kernel sees.
If you want to consider a P4 with two of its SMT threads idle as "fully
loaded" (true on some very high-performance fortran kernels), then that
is your business; you should turn off hyperthreading in the BIOS.
We would need a "FP functional unit issue rate per sec" metric to get a
true picture of "loaded".
-Federico
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