On Mon, Nov 18, 2024 at 6:10 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > On Sun, Nov 17, 2024 at 10:56:21AM +0800, Yafang Shao wrote: > > On Fri, Nov 15, 2024 at 9:41 PM Michal Koutný <mkoutny@xxxxxxxx> wrote: > > > > > The load balancer is malfunctioning due to the exclusion of IRQ time from > > > > CPU utilization calculations. > > > > > > Could this be fixed by subtracting (global) IRQ time from (presumed > > > total) system capacity that the balancer uses for its decisions? (i.e. > > > without exact per-cgroup breakdown of IRQ time) > > > > The issue here is that the global IRQ time may include the interrupted > > time of tasks outside the target cgroup. As a result, I don't believe > > it's possible to find a reliable solution without modifying the > > kernel. > > Since there is no relation between the interrupt and the interrupted > task (and through that its cgroup) -- all time might or might not be > part of your cgroup of interest. Consider it a random distribution if > you will. Some points require further clarification. On our servers, the majority of IRQ/softIRQ activity originates from network traffic, and we consistently enable Receive Flow Steering (RFS) [0]. This configuration ensures that softIRQs are more likely to interrupt the tasks responsible for processing the corresponding packets. As a result, the distribution of softIRQs is not random but instead closely aligned with the packet-handling tasks. [0]. https://lwn.net/Articles/381955/
