On Sat, May 27, 2023 at 05:07:34AM +0000, br...@mailbox.org wrote: > > On Sat, 27 May 2023, Mike Larkin wrote: > > > On Fri, May 26, 2023 at 08:14:23PM +0200, br...@mailbox.org wrote: > > > On 05/26/2023 8:08 PM CEST Mike Larkin <mlar...@nested.page> wrote: > > > > > > > > > > On Fri, May 26, 2023 at 07:16:09PM +0200, br...@mailbox.org wrote: > > > > > > On 05/26/2023 6:06 PM CEST Mike Larkin <mlar...@nested.page> wrote: > > > > > > > > > > > > perf top on the linux side to see where qemu is spending it's time? > > > > > > > > > > Sure, I ran `perf top -p $PID` with $PID being the PID of the QEMU > > > > > process and copied the screen after a few seconds. Let me know if you > > > > > intended something different: > > > > > > > > > > PerfTop: 133 irqs/sec kernel:72.9% exact: 0.0% lost: 0/0 > > > > > drop: 0/0 [4000Hz cycles], (target_pid: 9939) > > > > > -------------------------------------------------------------------------------------------------------------------------------------------------- > > > > > > > > > > 25.35% [kvm_amd] [k] svm_vcpu_run > > > > > 4.18% [kernel] [k] native_write_msr > > > > > 4.01% [kernel] [k] native_read_msr > > > > > 3.73% [kernel] [k] read_tsc > > > > > 3.64% [kvm] [k] kvm_arch_vcpu_ioctl_run > > > > > 2.21% [kvm_amd] [k] svm_vcpu_load > > > > > 1.98% [kernel] [k] ktime_get > > > > > 1.47% [kvm] [k] kvm_apic_has_interrupt > > > > > 1.40% [kernel] [k] restore_fpregs_from_fpstate > > > > > 1.29% [kvm] [k] apic_has_interrupt_for_ppr > > > > > 1.18% [kernel] [k] check_preemption_disabled > > > > > 1.10% [kernel] [k] x86_pmu_disable_all > > > > > 1.07% [kernel] [k] __srcu_read_lock > > > > > 1.07% [kernel] [k] newidle_balance > > > > > 1.03% [kvm] [k] kvm_pmu_trigger_event > > > > > 0.98% [kernel] [k] amd_pmu_addr_offset > > > > > > > > > > I tried this also on the FreeBSD VM and the irqs/sec were between 2 > > > > > and 4. > > > > > > > > > > > > > you might just be bombarded with ipis. how many vcpus? > > > > > > It should be 16, I use `-smp 16 -cpu host` > > > > > > > try with less and see if that works. > > With -smp 4 it's better although still worse than FreeBSD/Linux. In htop > OpenBSD is in the 1.3-2.6% range while the other OSes are at 0-0.7%. As I > said, the FreeBSD/Linux VMs continue to stay in the 0% even at -smp 16, > while I've seen OpenBSD idle at up to 7-8% with that.
probably IPI traffic then. not sure what else to say. If a few % host overhead is too much fot you with a 16 vCPU VM, I'd suggest reducing that. What is your workload for a 16 vcpu openbsd VM anyway?
