AIX CPU waits Post: 302645895

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Operating Systems AIX AIX CPU waits Post 302645895 by bakunin on Thursday 24th of May 2012 08:59:50 AM

05-24-2012

Registered User

CPU "wait"s mean: a process, ready to be run (again) cannot be run AND there is no other process which could be run instead. In this regard "wait" is a special kind of "idle" - one, where there are indeed processes to be run whereas "idle" takes place when there are no processes to be run at all.

It is true that - like mentioned in the paper "Demystifying I/O Wait". CPU-intensive processes running at the same time could mask I/O-waits because the processor time is given to these CPU-intensive processes while the I/O-bound process waits. This doesn't seem to be the case here, though.

To see a considerable number of waits always means: the I/O-part of the systems operation is the bottleneck. All the other parts of the system are faster than I/O. This is not necessarily bad: some part always is the weakest link in the chain and if it isn't I/O it would be something else. The question is: is the systems speed enough for you purposes? If this is the case you have nothing to do - once it isn't fast enough any more you will know where to start.

I hope this helps.

bakunin

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clock

clock(3C)																 clock(3C)

NAME

       clock() - report CPU time used

SYNOPSIS

DESCRIPTION

       returns	the amount of CPU time (in microseconds) used since the first call to The time reported is the sum of the user and system times of
       the calling process and its terminated child processes for which it has executed , or (see wait(2) , system(3S), and popen(3S)).  To deter-
       mine the time in seconds, the value returned by should be divided by the value of the macro

       The resolution of the clock varies, depending on the hardware and on software configuration.

       If the processor time used is not available or its value cannot be represented, the function returns the value

WARNINGS

       The  value returned by is defined in microseconds for compatibility with systems that have CPU clocks with much higher resolution.  Because
       of this, the value returned wraps around after accumulating only 4295 seconds of CPU time (about 72 minutes).

DEPENDENCIES

       The default clock resolution is 10 milliseconds.

SEE ALSO

       times(2), wait(2), system(3S), thread_safety(5).

STANDARDS CONFORMANCE

																	 clock(3C)

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