Messages in this thread | | | Date | Mon, 28 Mar 2022 12:44:54 -0400 | From | Steven Rostedt <> | Subject | Re: [External] Re: [PATCH] sched/fair: fix broken bandwidth control with nohz_full |
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On Mon, 28 Mar 2022 17:56:07 +0200 Peter Zijlstra <peterz@infradead.org> wrote:
> > echo $$ > test/cgroup.procs > > taskset -c 1 bash -c "while true; do let i++; done" --> will be throttled > > Ofcourse.. I'm arguing that bandiwdth control and NOHZ_FULL are somewhat > mutually exclusive, use-case wise. So I really don't get why you'd want > them both.
Is it?
One use case I can see for having both is for having a deadline task that needs to get something done in a tight deadline. NOHZ_FULL means "do not interrupt this task when it is the top priority task on the CPU and is running in user space".
Why is it mutually exclusive to have a deadline task that does not want to be interrupted by timer interrupts?
Just because the biggest pushers of NOHZ_FULL is for those that are running RT tasks completely in user space and event want to fault if it ever goes into the kernel, doesn't mean that's the only use case.
Chengming brought up VMs. That's a case to want to control the bandwidth, but also not interrupt them with timer interrupts when they are running as the top priority task on a CPU.
-- Steve
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