Messages in this thread | | | Date | Wed, 24 Jan 2024 13:14:40 +0100 | Subject | Re: [v2 0/4] KVM: irqchip: synchronize srcu only if needed | From | Christian Borntraeger <> |
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Am 21.01.24 um 12:17 schrieb Yi Wang: > From: Yi Wang <foxywang@tencent.com> > > 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.
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