CPU Affinity setting not sticking

I'm attempting to set the affinity of mysql (latest Percona Server) on a 4vCpu VPS virtualized with OpenVZ and running CentOS 6.x.

The command I'm running is taskset -pc 0-1 1026. I've also tried 0,1 instead. The output is:

pid 1026's current affinity list: 0-3
pid 1026's new affinity list: 0-3

So, it does not seem to be 'sticking'. It can be confirmed by running taskset again to find the cpu's available to the process. Is this an issue with my virtualization type, perhaps?

I'm doing this because every now and then I need mysql to run quite hard, and going over 2.0-4.0 for more than 2 hours gets me a restart with my current provider.

Is there a clear reason why this isn't working, or is more troubleshooting required?

CPU affinity masks are ignored inside OpenVZ containers. You will not be able to get this to "work".

In RHEL5-based kernels we had the notion of virtual cpus: tasks were scheduled on vcpus while the vcpus were somehow distributed among physical cpus. The sched_setaffinity syscall could be used to bind tasks to vcpus then.

This concept was cumbersome and often sub-optimal so in RHEL6 we decided to drop it: currently setting nr_cpus limit for a container is actually equivalent to setting cpulimit. The decision is justified by the fact that the latest Linux scheduler is smart enough to gather actively interacting tasks together so that there is no need to limit parallelism artificially.

As a result, cpu affinity support was dropped. Tasks can still use the sched_setaffinity syscall, but it will be ignored.

A tool like taskset probably won't work properly in a container. You may be able to do this from the host system, but it doesn't make sense from within a container.

See: Taskset not working properly in OpenVZ container