On Tue, Aug 31, 2021 at 09:59:19AM +0800, Tianqiang Xu wrote: > Guest OS uses 'is_idle' field of kvm_steal_time to know if a pCPU > is idle and decides whether to schedule a task to a preempted vCPU > or not. If the pCPU is idle, scheduling a task to this pCPU will > improve cpu utilization. If not, avoiding scheduling a task to this > preempted vCPU can avoid host/guest switch, hence improving performance. > > Guest OS invokes available_idle_cpu_sched() to get the value of > 'is_idle' field of kvm_steal_time. > > Other modules in kernel except kernel/sched/fair.c which invokes > available_idle_cpu() is left unchanged, because other modules in > kernel need the semantic provided by 'preempted' field of kvm_steal_time. > --- > kernel/sched/fair.c | 24 ++++++++++++------------ > 1 file changed, 12 insertions(+), 12 deletions(-) Goes and replaces every single available_idle_cpu() in fair with the new function that doesn't consider vCPU preemption. So what do you reckon now happens in the oversubscribed virt scenario where each CPU has multiple vCPUs?
