On Thu, Jun 10, 2021 at 03:16:29PM -0400, Waiman Long wrote: > 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. Oh, because it then creates a cgroup tree per CPU and you get to move tasks between cgroups? OK I suppose.
