On Wed, Mar 16, 2011 at 10:55:02PM +0300, Michael Tokarev wrote:
> 16.03.2011 22:48, Marcelo Tosatti wrote:
> > 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
> []
> >> After booting, idle guest sitting at login: prompt:
> >>
> >> host_state_reload 28675531 44171
> >> exits 25184108 3379
> >> insn_emulation 22784490 3266
> >> irq_injections 54139 200
> []
> >> 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:
> >>
>
> > Perhaps OpenBSD is accessing the HPET frequently, which is emulated
> > in userspace. Try disabling it with "-no-hpet".
>
> -no-hpet makes no visible difference, exactly the same thing as above:
>
> host_state_reload 21310655 43968
> exits 25007599 3573
> insn_emulation 22635201 3469
>
Can you do ftrace of kvm events?
--
Gleb.
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
