On Mon, 28 Feb 2022 at 09:27, Li,Rongqing <lirongqing@xxxxxxxxx> wrote: > > > On Fri, 25 Feb 2022 at 23:04, Li RongQing <lirongqing@xxxxxxxxx> wrote: > > > > > > When sending a call-function IPI-many to vCPUs, yield to the IPI > > > target vCPU which is marked as preempted. > > > > > > but when emulating HLT, an idling vCPU will be voluntarily scheduled > > > out and mark as preempted from the guest kernel perspective. yielding > > > to idle vCPU is pointless and increase unnecessary vmexit, maybe miss > > > the true preempted vCPU > > > > > > so yield to IPI target vCPU only if vCPU is busy and preempted > > > > This is not correct, there is an intention to boost the reactivation of idle vCPU, > > PV sched yield is used in over-subscribe scenario and the pCPU which idle vCPU is > > resident maybe busy, and the vCPU will wait in the host scheduler run queue. > > There is a research paper [1] focusing on this boost and showing better > > performance numbers, though their boost is more unfair. > > > > [1]. https://ieeexplore.ieee.org/document/8526900 > > "Accelerating Idle vCPU Reactivation" > > > > Wanpeng > > > I understand that over-subscribe system is not always over- subscribe, it should sometime true, sometime not. You should pay the pain if you do not tune your setup well. Wanpeng
