Reviewed: https://review.opendev.org/748251 Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=49a793c8ee7a9be26e4e3d6ddd097a6ee6fea29d Submitter: Zuul Branch: stable/ussuri commit 49a793c8ee7a9be26e4e3d6ddd097a6ee6fea29d Author: Stephen Finucane Date: Thu Jul 30 17:37:38 2020 +0100 tests: Add reproducer for bug #1889633 With the introduction of the cpu-resources work [1], (libvirt) hosts can now report 'PCPU' inventory separate from 'VCPU' inventory, which is consumed by instances with pinned CPUs ('hw:cpu_policy=dedicated'). As part of that effort, we had to drop support for the ability to boot instances with 'hw:cpu_thread_policy=isolate' (i.e. I don't want hyperthreads) on hosts with hyperthreading. This had been previously implemented by marking thread siblings of the host cores used by such an instance as reserved and unusable by other instances, but such a design wasn't possible in world where we had to track resource consumption in placement before landing in the host. Instead, the 'isolate' policy now simply means "give me a host without hyperthreads". This is enforced by hosts with hyperthreads reporting the 'HW_CPU_HYPERTHREADING' trait, and instances with the 'isolate' policy requesting 'HW_CPU_HYPERTHREADING=forbidden'. Or at least, that's how it should work. We also have a fallback query for placement to find hosts with 'VCPU' inventory and that doesn't care about the 'HW_CPU_HYPERTHREADING' trait. This was envisioned to ensure hosts with old style configuration ('[DEFAULT] vcpu_pin_set') could continue to be scheduled to. We figured that this second fallback query could accidentally pick up hosts with new-style configuration, but we are also tracking the available and used cores from those listed in the '[compute] cpu_dedicated_set' as part of the host 'NUMATopology' objects (specifically, via the 'pcpuset' and 'cpu_pinning' fields of the 'NUMACell' child objects). These are validated by both the 'NUMATopologyFilter' and the virt driver itself, which means hosts with new style configuration that got caught up in this second query would be rejected by this filter or by a late failure on the host. (Hint: there's much more detail on this in the spec). Unfortunately we didn't think about hyperthreading. If a host gets picked up in the second request, it might well have enough PCPU inventory but simply be rejected in the first query since it had hyperthreads. In this case, because it has enough free cores available for pinning, neither the filter nor the virt driver will reject the request, resulting in a situation whereby the instance ends up falling back to the old code paths and consuming $flavor.vcpu host cores, plus the thread siblings for each of these cores. Despite this, it will be marked as consuming $flavor.vcpu VCPU (not PCPU) inventory in placement. This patch proves this to be the case, allowing us to resolve the issue later. [1] https://specs.openstack.org/openstack/nova-specs/specs/train/approved/cpu-resources.html Change-Id: I87cd4d14192b1a40cbdca6e3af0f818f2cab613e Signed-off-by: Stephen Finucane