 | | | Meaning of 'load ' on Linux | Meaning of 'load ' on Linux 2005-06-17 - By John Haxby
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Viggiani Domenico wrote:
>I'm sure that a load of 8/10 makes an HP-UX box pratically unusable while,
>as you say, sometime it's normal to have a Linux box with a load of 50.
>In addition, as a sensation, when submitting jobs to an HP-UX system, it
>seeems that load increases slightly and linearly.
>Linux instead absorbs jos with sudden rise of load.
>
>
How the system absorbs load is much more a characteristic of hardware
than of the kernel.
When I used to work for HP, my workstation (an HP box) would be
noticably sluggish one the load average got above about 2. On the
other hand, the server hosting ClearCase and whatnot for development
generally ran at fairly high load averages -- it wasn't the number of
CPUs (it had just the one) it was that it was set up for serious I/O all
the way through the hardware -- disks, controllers, mainboard design,
etc. We used to do performance tests on serious hardware with lots of
memory, lots of disks and several (4 or 8) CPUs. Load averages during
a performance test run were certainly around 50, if not more, and the
response times for individual server requests were well within what we
considered acceptable (and not actually all that much different to an
unloaded system -- the limitation on performance was generally the
number of I/O transfers per second.)
My Linux dual-processor box tended to be better than my HP box but that
was down to having two processors and more memory and had little or
nothing to do with the OS. The HP box was significantl faster for some
types of computation, just not the types that I used :-(
Sticking with my time at HP, the Linux servers we had at the time had
almost identical performance to the equivalent HP/UX servers. If you
set up a system with a couple of CPUs, a decent raid array and enough
memory it made practically no difference whether it was Linux/Intel or
HP-UX/PA-RISC. Later on we found we could do the same trick with
Solaris/Space and AIX/whatever. The Z-series is a little weird by
comparison, but the numbers are recognisably the same.
jch
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