On 11/07/16 17:10, Waiman Long wrote: > On 07/06/2016 02:52 AM, Peter Zijlstra wrote: >> On Tue, Jun 28, 2016 at 10:43:07AM -0400, Pan Xinhui wrote: >>> change fomr v1: >>> a simplier definition of default vcpu_is_preempted >>> skip mahcine type check on ppc, and add config. remove dedicated >>> macro. >>> add one patch to drop overload of rwsem_spin_on_owner and >>> mutex_spin_on_owner. >>> add more comments >>> thanks boqun and Peter's suggestion. >>> >>> This patch set aims to fix lock holder preemption issues. >>> >>> test-case: >>> perf record -a perf bench sched messaging -g 400 -p&& perf report >>> >>> 18.09% sched-messaging [kernel.vmlinux] [k] osq_lock >>> 12.28% sched-messaging [kernel.vmlinux] [k] rwsem_spin_on_owner >>> 5.27% sched-messaging [kernel.vmlinux] [k] mutex_unlock >>> 3.89% sched-messaging [kernel.vmlinux] [k] wait_consider_task >>> 3.64% sched-messaging [kernel.vmlinux] [k] _raw_write_lock_irq >>> 3.41% sched-messaging [kernel.vmlinux] [k] mutex_spin_on_owner.is >>> 2.49% sched-messaging [kernel.vmlinux] [k] system_call >>> >>> We introduce interface bool vcpu_is_preempted(int cpu) and use it in >>> some spin >>> loops of osq_lock, rwsem_spin_on_owner and mutex_spin_on_owner. >>> These spin_on_onwer variant also cause rcu stall before we apply this >>> patch set >>> >> Paolo, could you help out with an (x86) KVM interface for this? >> >> Waiman, could you see if you can utilize this to get rid of the >> SPIN_THRESHOLD in qspinlock_paravirt? > > That API is certainly useful to make the paravirt spinlock perform > better. However, I am not sure if we can completely get rid of the > SPIN_THRESHOLD at this point. It is not just the kvm, the xen code need > to be modified as well. This should be rather easy. The relevant information is included in the runstate data mapped into kernel memory. I can provide a patch for Xen if needed. Juergen _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
