On Wed, Jan 24, 2024 at 8:14 PM Christian Borntraeger <borntraeger@xxxxxxxxxxxxx> wrote: > > Am 21.01.24 um 12:17 schrieb Yi Wang: > > From: Yi Wang <foxywang@xxxxxxxxxxx> > > > > We found that it may cost more than 20 milliseconds very accidentally > > to enable cap of KVM_CAP_SPLIT_IRQCHIP on a host which has many vms > > already. > > > > The reason is that when vmm(qemu/CloudHypervisor) invokes > > KVM_CAP_SPLIT_IRQCHIP kvm will call synchronize_srcu_expedited() and > > might_sleep and kworker of srcu may cost some delay during this period. > > One way makes sence is setup empty irq routing when creating vm and > > so that x86/s390 don't need to setup empty/dummy irq routing. > > > > Note: I have no s390 machine so the s390 patch has not been tested. > > I just did a quick sniff and it still seems to work. No performance check etc. Thanks very much, Christian! --- Best wishes Yi Wang
