On Wed, Jan 05, 2022 at 07:46:55PM -0500, Daniel Jordan wrote: > As before, helpers in multithreaded jobs don't honor the main thread's > CFS bandwidth limits, which could lead to the group exceeding its quota. > > Fix it by having helpers remote charge their CPU time to the main > thread's task group. A helper calls a pair of new interfaces > cpu_cgroup_remote_begin() and cpu_cgroup_remote_charge() (see function > header comments) to achieve this. > > This is just supposed to start a discussion, so it's pretty simple. > Once a kthread has finished a remote charging period with > cpu_cgroup_remote_charge(), its runtime is subtracted from the target > task group's runtime (cfs_bandwidth::runtime) and any remainder is saved > as debt (cfs_bandwidth::debt) to pay off in later periods. > > Remote charging tasks aren't throttled when the group reaches its quota, > and a task group doesn't run at all until its debt is completely paid, > but these shortcomings can be addressed if the approach ends up being > taken. > *groan*... and not a single word on why it wouldn't be much better to simply move the task into the relevant cgroup..
