Re: *insane* amount of host_state_reloads for openbsd guest in 0.14

[Michael Tokarev <mjt@tls.msk.ru>]

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

Thanks!

/mjt