Talks > 15-16/10/2012

CPU Core Binding: tight rein your user processes

Some users are liars, cheaters or at best they don’t fully understand what they are doing. Luckily only a small part of a cluster’s users behaves this way but they can adversely affect the work of the other users who play by the rules.

The type of jobs executed in the LSI cluster are so diverse: commercial software like Matlab, Maple and CPLEX, proprietary software programmed in C, Java, Python,… Currently our policy states that a user may reserve as many slots as real cores need to complete its work. As a result we have a 1:1 slot-cpu ratio.

The execution of single process/single threaded jobs is not a problem: they request one slot and consume one core. However in processes with some level of parallelism, sometimes hidden for a regular user (some Matlab libraries are parallel, Java use threads, …), the core usage does not correspond to the amount of requested slots.

Furthermore, we can set load limits to prevent overloading nodes, but this does not solve the problem and we don’t avoid the possible collapse of the node. On the other hand load limits neither prevents honest users to be penalized.

Using the core binding technique, the CPU affinity mechanism implemented in all the forks of Grid Engine, we can force jobs to use exactly as many cores as reserved slots. Jobs’ processes will remain confined in their assigned cores.

Thus we get a dual goal. We solve the problem with the execution of parallel processes (accounting, overloading, cheating), and we improve the execution time of many processes due to the core confinement avoiding system context switch.


Related Talks

Visit our forum

One of the main goals of this project is to motivate new initiatives and collaborations in the HPC field. Visit our forum to share your knowledge and discuss with other HPC experts!

About us

HPCKP (High-Performance Computing Knowledge Portal) is an Open Knowledge project focused on technology transfer and knowledge sharing in the HPC Science field.

HPC Knowledge Portal is supported and maintained by HPCNow!