Sergio Lopez 0e4e27ea9d vhost_user_block: Make use of the EVENT_IDX feature ... Now that vhost_user_backend and vm-virtio do support EVENT_IDX, use it in vhost_user_block to reduce the number of notifications sent between the driver and the device. This is specially useful when using active polling on the virtqueue, as it'll be implemented by a future patch. This is a snapshot of kvm_stat while generating ~60K IOPS with fio on the guest without EVENT_IDX: Event Total %Total CurAvg/s kvm_entry 393454 20.3 62494 kvm_exit 393446 20.3 62494 kvm_apic_accept_irq 378146 19.5 60268 kvm_msi_set_irq 369720 19.0 58881 kvm_fast_mmio 370497 19.1 58817 kvm_hv_timer_state 10197 0.5 1715 kvm_msr 8770 0.5 1443 kvm_wait_lapic_expire 7018 0.4 1118 kvm_apic 2768 0.1 538 kvm_pv_tlb_flush 2028 0.1 360 kvm_vcpu_wakeup 1453 0.1 278 kvm_apic_ipi 1384 0.1 269 kvm_fpu 1148 0.1 164 kvm_pio 574 0.0 82 kvm_userspace_exit 574 0.0 82 kvm_halt_poll_ns 24 0.0 3 And this is the snapshot while doing the same thing with EVENT_IDX: Event Total %Total CurAvg/s kvm_entry 35506 26.0 3873 kvm_exit 35499 26.0 3873 kvm_hv_timer_state 14740 10.8 1672 kvm_apic_accept_irq 13017 9.5 1438 kvm_msr 12845 9.4 1421 kvm_wait_lapic_expire 10422 7.6 1118 kvm_apic 3788 2.8 502 kvm_pv_tlb_flush 2708 2.0 340 kvm_vcpu_wakeup 1992 1.5 258 kvm_apic_ipi 1894 1.4 251 kvm_fpu 1476 1.1 164 kvm_pio 738 0.5 82 kvm_userspace_exit 738 0.5 82 kvm_msi_set_irq 701 0.5 69 kvm_fast_mmio 238 0.2 4 kvm_halt_poll_ns 50 0.0 1 kvm_ple_window_update 28 0.0 0 kvm_page_fault 4 0.0 0 It can be clearly appreciated how the number of vm exits per second, specially the ones related to notifications (kvm_fast_mmio and kvm_msi_set_irq) is drastically lower. Signed-off-by: Sergio Lopez <slp@redhat.com>		2020-02-19 17:13:47 +00:00
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src	vhost_user_block: Make use of the EVENT_IDX feature	2020-02-19 17:13:47 +00:00
Cargo.toml	vhost_user_block: Refactor vhost_user_block backend code into a new crate	2020-01-23 10:30:06 +00:00