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SubjectRe: [PATCH v3 6/9] cgroup/cpuset: Add a new isolated cpus.partition type
On Tue, Jul 20, 2021 at 10:18:31AM -0400, Waiman Long wrote:
> Bugzilla:
> commit 994fb794cb252edd124a46ca0994e37a4726a100
> Author: Waiman Long <>
> Date: Sat, 19 Jun 2021 13:28:19 -0400
> cgroup/cpuset: Add a new isolated cpus.partition type
> 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.
> To address this issue for cpuset v2, a new cpuset.cpus.partition type
> "isolated" is added which allows the creation of a cpuset partition
> without load balancing. This will allow system administrators to
> dynamically adjust the size of isolated partition to the current need
> of the workload without rebooting the system.
> Signed-off-by: Waiman Long <>
> Signed-off-by: Waiman Long <>

Nice! And while we are adding a new ABI, can we take advantage of that and
add a specific semantic that if a new isolated partition matches a subset of
"isolcpus=", it automatically maps to it. This means that any further
modification to that isolated partition will also modify the associated
isolcpus= subset.

Or to summarize, when we create a new isolated partition, remove the associated
CPUs from isolcpus= ?


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