Messages in this thread |  | | Date | Wed, 12 Jan 2022 10:40:01 -0500 | Subject | Re: [PATCH v9 4/7] cgroup/cpuset: Add a new isolated cpus.partition type | From | Waiman Long <> |
| |
On 1/12/22 10:21, Peter Zijlstra wrote: > On Sun, Dec 05, 2021 at 01:32:17PM -0500, 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 >> "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. > you can, ofcourse, create lots of 1 cpu partitions, which is effectively > what you're doing, except there was a problem with that which you also > forgot to mention.
Yes, that is a possible workaround. However, it makes cgroup management much harder especially in the cgroup v2 environment where multiple controllers are likely to be enabled in the same cgroup.
Cheers, Longman
|  |