On Thu, 2014-09-11 at 15:25 -0400, Bogdan Purcareata wrote: > This patch enables running intensive I/O workloads, e.g. netperf, in a guest > deployed on a RT host. No change for !RT kernels. > > The openpic spinlock becomes a sleeping mutex on a RT system. This no longer > guarantees that EPR is atomic with exception delivery. The guest VCPU thread > fails due to a BUG_ON(preemptible()) when running netperf. > > In order to make the kvmppc_mpic_set_epr() call safe on RT from non-atomic > context, convert the openpic lock to a raw_spinlock. A similar approach can > be seen for x86 platforms in the following commit [1]. > > Here are some comparative cyclitest measurements run inside a high priority RT > guest run on a RT host. The guest has 1 VCPU and the test has been run for 15 > minutes. The guest runs ~750 hackbench processes as background stress. Does hackbench involve triggering interrupts that would go through the MPIC? You may want to try an I/O-heavy benchmark to stress the MPIC code (the more interrupt sources are active at once, the "better"). Also try a guest with many vcpus. -Scott -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
