Re: [PATCH 2/5] cgroup/cpuset: Add new cpus.partition type with no load balancing

Peter Zijlstra
2021-06-10T19:00:50Z

On Thu, Jun 03, 2021 at 05:24:13PM -0400, Waiman Long wrote:
> Cpuset v1 uses the sched_load_balance control file to determine if load
> balancing should be enabled. Cpuset v2 gets rid of sched_load_balance
> as its use may require disabling load balancing at cgroup root.
>
> For workloads that require very low latency like DPDK, the latency
> jitters caused by periodic load balancing may exceed the desired
> latency limit.
>
> When cpuset v2 is in use, the only way to avoid this latency cost is to
> use the "isolcpus=" kernel boot option to isolate a set of CPUs. After
> the kernel boot, however, there is no way to add or remove CPUs from
> this isolated set. For workloads that are more dynamic in nature, that
> means users have to provision enough CPUs for the worst case situation
> resulting in excess idle CPUs.

Also, can we change isolcpus to create a default cgroup hierarchy
instead of being the fugly hack that it is? I really hate isolcpus with
a passion, it needs to die.