ab9cf4996b
The idea is simple: there's a bit, per APIC, in guest memory,
that tells the guest that it does not need EOI.
Guest tests it using a single est and clear operation - this is
necessary so that host can detect interrupt nesting - and if set, it can
skip the EOI MSR.
I run a simple microbenchmark to show exit reduction
(note: for testing, need to apply follow-up patch
'kvm: host side for eoi optimization' + a qemu patch
I posted separately, on host):
Before:
Performance counter stats for 'sleep 1s':
47,357 kvm:kvm_entry [99.98%]
0 kvm:kvm_hypercall [99.98%]
0 kvm:kvm_hv_hypercall [99.98%]
5,001 kvm:kvm_pio [99.98%]
0 kvm:kvm_cpuid [99.98%]
22,124 kvm:kvm_apic [99.98%]
49,849 kvm:kvm_exit [99.98%]
21,115 kvm:kvm_inj_virq [99.98%]
0 kvm:kvm_inj_exception [99.98%]
0 kvm:kvm_page_fault [99.98%]
22,937 kvm:kvm_msr [99.98%]
0 kvm:kvm_cr [99.98%]
0 kvm:kvm_pic_set_irq [99.98%]
0 kvm:kvm_apic_ipi [99.98%]
22,207 kvm:kvm_apic_accept_irq [99.98%]
22,421 kvm:kvm_eoi [99.98%]
0 kvm:kvm_pv_eoi [99.99%]
0 kvm:kvm_nested_vmrun [99.99%]
0 kvm:kvm_nested_intercepts [99.99%]
0 kvm:kvm_nested_vmexit [99.99%]
0 kvm:kvm_nested_vmexit_inject [99.99%]
0 kvm:kvm_nested_intr_vmexit [99.99%]
0 kvm:kvm_invlpga [99.99%]
0 kvm:kvm_skinit [99.99%]
57 kvm:kvm_emulate_insn [99.99%]
0 kvm:vcpu_match_mmio [99.99%]
0 kvm:kvm_userspace_exit [99.99%]
2 kvm:kvm_set_irq [99.99%]
2 kvm:kvm_ioapic_set_irq [99.99%]
23,609 kvm:kvm_msi_set_irq [99.99%]
1 kvm:kvm_ack_irq [99.99%]
131 kvm:kvm_mmio [99.99%]
226 kvm:kvm_fpu [100.00%]
0 kvm:kvm_age_page [100.00%]
0 kvm:kvm_try_async_get_page [100.00%]
0 kvm:kvm_async_pf_doublefault [100.00%]
0 kvm:kvm_async_pf_not_present [100.00%]
0 kvm:kvm_async_pf_ready [100.00%]
0 kvm:kvm_async_pf_completed
1.002100578 seconds time elapsed
After:
Performance counter stats for 'sleep 1s':
28,354 kvm:kvm_entry [99.98%]
0 kvm:kvm_hypercall [99.98%]
0 kvm:kvm_hv_hypercall [99.98%]
1,347 kvm:kvm_pio [99.98%]
0 kvm:kvm_cpuid [99.98%]
1,931 kvm:kvm_apic [99.98%]
29,595 kvm:kvm_exit [99.98%]
24,884 kvm:kvm_inj_virq [99.98%]
0 kvm:kvm_inj_exception [99.98%]
0 kvm:kvm_page_fault [99.98%]
1,986 kvm:kvm_msr [99.98%]
0 kvm:kvm_cr [99.98%]
0 kvm:kvm_pic_set_irq [99.98%]
0 kvm:kvm_apic_ipi [99.99%]
25,953 kvm:kvm_apic_accept_irq [99.99%]
26,132 kvm:kvm_eoi [99.99%]
26,593 kvm:kvm_pv_eoi [99.99%]
0 kvm:kvm_nested_vmrun [99.99%]
0 kvm:kvm_nested_intercepts [99.99%]
0 kvm:kvm_nested_vmexit [99.99%]
0 kvm:kvm_nested_vmexit_inject [99.99%]
0 kvm:kvm_nested_intr_vmexit [99.99%]
0 kvm:kvm_invlpga [99.99%]
0 kvm:kvm_skinit [99.99%]
284 kvm:kvm_emulate_insn [99.99%]
68 kvm:vcpu_match_mmio [99.99%]
68 kvm:kvm_userspace_exit [99.99%]
2 kvm:kvm_set_irq [99.99%]
2 kvm:kvm_ioapic_set_irq [99.99%]
28,288 kvm:kvm_msi_set_irq [99.99%]
1 kvm:kvm_ack_irq [99.99%]
131 kvm:kvm_mmio [100.00%]
588 kvm:kvm_fpu [100.00%]
0 kvm:kvm_age_page [100.00%]
0 kvm:kvm_try_async_get_page [100.00%]
0 kvm:kvm_async_pf_doublefault [100.00%]
0 kvm:kvm_async_pf_not_present [100.00%]
0 kvm:kvm_async_pf_ready [100.00%]
0 kvm:kvm_async_pf_completed
1.002039622 seconds time elapsed
We see that # of exits is almost halved.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
|
||
|---|---|---|
| .. | ||
| acpi | ||
| apic | ||
| cpu | ||
| .gitignore | ||
| alternative.c | ||
| amd_gart_64.c | ||
| amd_nb.c | ||
| apb_timer.c | ||
| aperture_64.c | ||
| apm_32.c | ||
| asm-offsets.c | ||
| asm-offsets_32.c | ||
| asm-offsets_64.c | ||
| audit_64.c | ||
| bootflag.c | ||
| check.c | ||
| cpuid.c | ||
| crash.c | ||
| crash_dump_32.c | ||
| crash_dump_64.c | ||
| devicetree.c | ||
| doublefault_32.c | ||
| dumpstack.c | ||
| dumpstack_32.c | ||
| dumpstack_64.c | ||
| e820.c | ||
| early-quirks.c | ||
| early_printk.c | ||
| entry_32.S | ||
| entry_64.S | ||
| ftrace.c | ||
| head.c | ||
| head32.c | ||
| head64.c | ||
| head_32.S | ||
| head_64.S | ||
| hpet.c | ||
| hw_breakpoint.c | ||
| i386_ksyms_32.c | ||
| i387.c | ||
| i8237.c | ||
| i8253.c | ||
| i8259.c | ||
| io_delay.c | ||
| ioport.c | ||
| irq.c | ||
| irq_32.c | ||
| irq_64.c | ||
| irq_work.c | ||
| irqinit.c | ||
| jump_label.c | ||
| kdebugfs.c | ||
| kgdb.c | ||
| kprobes-common.h | ||
| kprobes-opt.c | ||
| kprobes.c | ||
| kvm.c | ||
| kvmclock.c | ||
| ldt.c | ||
| machine_kexec_32.c | ||
| machine_kexec_64.c | ||
| Makefile | ||
| microcode_amd.c | ||
| microcode_core.c | ||
| microcode_intel.c | ||
| mmconf-fam10h_64.c | ||
| module.c | ||
| mpparse.c | ||
| msr.c | ||
| nmi.c | ||
| nmi_selftest.c | ||
| paravirt-spinlocks.c | ||
| paravirt.c | ||
| paravirt_patch_32.c | ||
| paravirt_patch_64.c | ||
| pci-calgary_64.c | ||
| pci-dma.c | ||
| pci-iommu_table.c | ||
| pci-nommu.c | ||
| pci-swiotlb.c | ||
| pcspeaker.c | ||
| probe_roms.c | ||
| process.c | ||
| process_32.c | ||
| process_64.c | ||
| ptrace.c | ||
| pvclock.c | ||
| quirks.c | ||
| reboot.c | ||
| reboot_fixups_32.c | ||
| relocate_kernel_32.S | ||
| relocate_kernel_64.S | ||
| resource.c | ||
| rtc.c | ||
| setup.c | ||
| setup_percpu.c | ||
| signal.c | ||
| smp.c | ||
| smpboot.c | ||
| stacktrace.c | ||
| step.c | ||
| sys_i386_32.c | ||
| sys_x86_64.c | ||
| syscall_32.c | ||
| syscall_64.c | ||
| tboot.c | ||
| tce_64.c | ||
| test_nx.c | ||
| test_rodata.c | ||
| time.c | ||
| tls.c | ||
| tls.h | ||
| topology.c | ||
| traps.c | ||
| tsc.c | ||
| tsc_sync.c | ||
| uprobes.c | ||
| verify_cpu.S | ||
| vm86_32.c | ||
| vmlinux.lds.S | ||
| vsmp_64.c | ||
| vsyscall_64.c | ||
| vsyscall_emu_64.S | ||
| vsyscall_trace.h | ||
| x86_init.c | ||
| x8664_ksyms_64.c | ||
| xsave.c | ||