PBS Questions


I’ve run a PBS job and qstat shows the following: resources_used.cpupercent = 196 How is it possible to use more than 100% of cpus?

The PBS system regularly polls all of the running jobs every 120 seconds. At each polling cycle it calculates an integer value called cpupercent. This is a moving weighted average of CPU usage for the cycle, given as the average percentage usage of one CPU. For example, a value of 50 means that during a certain period, the job used 50 percent of one CPU. A value of 300 means that during the period, the job used an average of three CPUs.

Therefore, if your job just uses one core it should be showing 100 cpupercent. If your job can use multiple cores and you have asked for 32 cores it should be showing 3200 cpupercent. If its a lot less then your job is not running efficiently.


I’ve run a PBS job and qstat shows the following:

resources_used.mem = 656112kb     <== about 0.6 GB
resources_used.vmem = 5038504kb   <== about 5 GB

What is “vmem”?

This is “virtual memory. Virtual memory includes the physical RAM that was used plus any files on disk that have been mapped into memory plus any “swap” memory used. Some applications allocate lots of virtual memory even if they only need a fraction. In most cases you can just ignore this value.

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