Messages in this thread | | | From | Waiman Long <> | Subject | Re: [PATCH 2/5] cgroup/cpuset: Add new cpus.partition type with no load balancing | Date | Thu, 10 Jun 2021 15:16:29 -0400 |
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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
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