Re: [PATCH] KVM: s390: improve interrupt cpu for wakeup

[Christian Borntraeger <borntraeger@linux.ibm.com>]

Am 04.09.25 um 13:39 schrieb Christian Borntraeger:
> Turns out that picking an idle CPU for floating interrupts has some
> negative side effects. The guest will keep the IO workload on its CPU
> and rather use an IPI from the interrupt CPU instead of moving workload.
> For example a guest with 2 vCPUss and 1 fio process might run that fio on
> vcpu1. If after diag500 both vCPUs are idle then vcpu0 is woken up. The
> guest will then do an IPI from vcpu0 to vcpu1.
> 
> So lets change the heuristics and prefer the last CPU that went to
> sleep. This one is likely still in halt polling and can be woken up
> quickly.
> 
> This patch shows significant improvements in terms of bandwidth or
> cpu consumption for fio and uperf workloads and seems to be a net
> win.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@linux.ibm.com>


applied internally for CI regression runs. Will push to next if successful.