On Thu, Aug 02, 2018 at 04:53:30AM +0000, Linaro QA wrote:
qemu_arm64: kselftest: * timers_rtcpie
* test src: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
This one is about RTC tests using userland. It is broken for 64Hz. It is close to the 1ms timeslice limit (even for weighted vruntime) of CFS. Same as:
https://bugs.linaro.org/show_bug.cgi?id=3402
My last comment: https://bugs.linaro.org/show_bug.cgi?id=3402#c12
Summarizes the issue. I'm thinking in proposing a change to upstream: ignore 64 Hz tests for virtual machines and/or systems with less than 4 CPUs. At the end, it does not make much sense to check RTC deviations using userland. Another possibility would be to test this using a simple module to be loaded just for the test, when no scheduler limits would apply for the IRQ handlers.
PS: Having KVM VMs, using virtio realtime clock implementations, will help for this BUT won't remove the min 1ms timeslice of CFS (that makes this test also fail in boards with less cores, like x15).