On Fri, Mar 11, 2011 at 03:02:33PM +0300, Michael Tokarev wrote: > I tried Openbsd 4.8 in kvm today and immediately noticed > that it is running _very_ slow, boot takes several minutes > to complete to the "login:" prompt. After investigating > I found that kvm does really insane amount of host_state_reloads. > Here are typical kvm_stats: > > During bootup while checking/mounting filesystems etc: > > host_state_reload 13782074 671689 > exits 24071297 45751 > insn_emulation 21707073 45353 > io_exits 6900215 288 > mmio_exits 20057 226 > irq_injections 6533 223 > pf_fixed 9801 176 > mmu_pte_write 17781 111 > irq_exits 6490 20 > fpu_reload 133 1 > halt_exits 422 0 > mmu_cache_miss 333 0 > halt_wakeup 30 0 > mmu_shadow_zapped 358 0 > remote_tlb_flush 3 0 > signal_exits 1 0 > > > After booting, idle guest sitting at login: prompt: > > host_state_reload 28675531 44171 > exits 25184108 3379 > insn_emulation 22784490 3266 > irq_injections 54139 200 > mmio_exits 52748 122 > mmu_pte_write 41584 100 > halt_exits 22731 99 > irq_exits 9220 12 > io_exits 6912620 9 > fpu_reload 765 1 > pf_fixed 12419 0 > mmu_shadow_zapped 358 0 > mmu_cache_miss 339 0 > halt_wakeup 38 0 > remote_tlb_flush 3 0 > signal_exits 1 0 > > > So I played with various options for a bit and found that: > > o 0.14 -no-kvm-irqchip gets rid of host_state_reloads, making > them to be the same (+/-100) as insn_emulations, and speeds > up guest significantly (and lowers CPU usage on host during > guest idle time). > > o 0.14 -no-kvm makes the guest *faster* than w/o any additional > options, reducing boot time for about 50% (but increasing host > CPU usage to maximum) > > o 0.12 without any options is the fastest, and it keeps number > of reloads to be within 3k/sec range during all time. here's > typical kvm_stats of idle guest with 0.12: > > kvm 0.12 and idle guest: > > exits 25975600 3329 > insn_emulation 23555272 3229 > host_state_reload 1898575 3117 > irq_injections 13125 200 > mmio_exits 26603 122 > mmu_pte_write 61515 100 > halt_exits 5173 100 > irq_exits 6927 1 > fpu_reload 499 1 > io_exits 7058999 1 > pf_fixed 11902 0 > mmu_shadow_zapped 634 0 > mmu_cache_miss 558 0 > halt_wakeup 166 0 > remote_tlb_flush 2 0 > signal_exits 1 0 > > > Again, running on the same AthlonII machine with 2.6.37 host > kernel, freshly installed openbsd 4.3 32bit guest (with all > defaults). > > FreeBSD does not show this behavour. > > What it can be? Perhaps OpenBSD is accessing the HPET frequently, which is emulated in userspace. Try disabling it with "-no-hpet". -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
