On Wed, 2015-02-18 at 09:32 +0000, Bogdan Purcareata wrote: > This patch enables running intensive I/O workloads, e.g. netperf, in a guest > deployed on a RT host. It also enable guests to be SMP. > > 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. > > spinlock raw_spinlock > Min latency (us) 4 4 > Avg latency (us) 15 19 > Max latency (us) 70 62 > > [1] https://lkml.org/lkml/2010/1/11/289 > > Signed-off-by: Bogdan Purcareata <bogdan.purcareata@xxxxxxxxxxxxx> > Reviewed-by: Scott Wood <scottwood@xxxxxxxxxxxxx> Where did that Reviewed-by: come from? A +1 in Gerrit on an internal tree does not translate into an upstream Reviewed-by. -Scott -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
