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RHEL6/CentOS6 high CPU use when idle

Reference Number: AA-01725 Views: 9154 0 Rating/ Voters

Since we introduced support for Red Hat-6 / CentOS-6 64-bit for LumenVox products, we have had reports from customers seeing higher than expected idle CPU use being reported for the Media Server when compared with the same version of LumenVox installed on an equivalent Red Hat 5 / CentOS 5 64-bit machine.

We have also noticed this apparent increase in CPU use and were concerned about it too, however it appears this is related to the new Completely Fair Scheduler (CFS) that was introduced in Red Hat/CentOS 6, and it is this difference that we attribute the change in idle CPU use being reported.

LumenVox are continually testing performance of our products on a number of platforms at varying loads, and although the idle CPU use being reported appears alarming, this does not appear to be affecting performance whenever the Media Server or another process requires proportionately more CPU time when busy.

There are independent reports describing these important changes to the scheduler in these later versions of Linux Operating Systems:

We will continue to monitor changes that affect CPU performance in Red Hat 6/CentOS 6 and will update this article as fixes or changes become available.

In the meantime, we do not believe that the high reported CPU time (in cases up to 20% of available CPU time when idle) actually affect performance when the Media Server is not idle, and this does not appear to have an appreciable impact on overall performance.

If users prefer to avoid this potential issue, installing Red Hat 5 or CentOS 5 64-bit does not exhibit this behavior with essentially the same LumenVox code.