On 6/10/21 2:50 PM, Peter Zijlstra wrote:
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.
To address this issue for cpuset v2, a new cpuset.cpus.partition type
"root-nolb" is added which allows the creation of a cpuset partition with
no load balancing. This will allow system administrators to dynamically
adjust the size of the no load balancing partition to the current need
of the workload without rebooting the system.
I'm confused, why do you need this? Just create a parition for each cpu.
From a management point of view, it is more cumbersome to do one cpu
per partition. I have suggested this idea of 1 cpu per partition to the
container developers, but they don't seem to like it.
Cheers,
Longman
