Re: [PATCH] don't call adjust_vmx_controls() second time

[Andrew Theurer <habanero@linux.vnet.ibm.com>]

Avi Kivity wrote:
> On 08/27/2009 11:42 PM, Andrew Theurer wrote:
>> On Thu, 2009-08-27 at 19:21 +0300, Avi Kivity wrote:
>>   
>>> On 08/27/2009 06:41 PM, Gleb Natapov wrote:
>>>     
>>>> Don't call adjust_vmx_controls() two times for the same control.
>>>> It restores options that was dropped earlier.
>>>>
>>>>        
>>> Applied, thanks.  Andrew, if you rerun your benchmark atop kvm.git
>>> 'next' branch, I believe you will see dramatically better results.
>>>      
>> Yes!  CPU is much lower:
>> user  nice  system   irq softirq  guest   idle  iowait
>> 5.81  0.00    9.48  0.08    1.04  21.32  57.86    4.41
>>
>> previous CPU:
>> user  nice  system   irq  softirq guest   idle  iowait
>> 5.67  0.00   11.64  0.09     1.05 31.90  46.06    3.59
>>
>>    
> 
> How does it compare to the other hypervisor now?

My original results for other hypervisor were a little inaccurate.  They 
mistakenly used 2 vcpu guests. New runs with 1 vcpu guests (as used in 
kvm) have slightly lower CPU utilization.  Anyway, here's the breakdown:

                                CPU       percent more CPU
kvm-master/qemu-kvm-87:        50.15     78%
kvm-next/qemu-kvm-87:          37.73     34%

> 
>> new oprofile:
>>
>>   
>>> samples  %        app name                 symbol name
>>> 885444   53.2905  kvm-intel.ko             vmx_vcpu_run
>>>      
> 
> guest mode = good
> 
>>> 38090     2.2924  qemu-system-x86_64       cpu_physical_memory_rw
>>> 34764     2.0923  qemu-system-x86_64       phys_page_find_alloc
>>> 14730     0.8865  qemu-system-x86_64       qemu_get_ram_ptr
>>> 10814     0.6508  vmlinux-2.6.31-rc5-autokern1 copy_user_generic_string
>>> 10871     0.6543  qemu-system-x86_64       virtqueue_get_head
>>> 8557      0.5150  qemu-system-x86_64       virtqueue_avail_bytes
>>> 7173      0.4317  qemu-system-x86_64       lduw_phys
>>> 4122      0.2481  qemu-system-x86_64       ldl_phys
>>> 3339      0.2010  qemu-system-x86_64       virtqueue_num_heads
>>> 4129      0.2485  libpthread-2.5.so        pthread_mutex_lock
>>>
>>>      
> 
> virtio and related qemu overhead: 8.2%.
> 
>>> 25278     1.5214  vmlinux-2.6.31-rc5-autokern1 native_write_msr_safe
>>> 12278     0.7390  vmlinux-2.6.31-rc5-autokern1 native_read_msr_safe
>>>      
> 
> This will be reduced to if we move virtio to kernel context.

Are there plans to move that to kernel for disk, too?

>>> 12380     0.7451  vmlinux-2.6.31-rc5-autokern1 native_set_debugreg
>>> 3550      0.2137  vmlinux-2.6.31-rc5-autokern1 native_get_debugreg
>>>      
> 
> A lot less than before, but still annoying.
> 
>>> 4631      0.2787  vmlinux-2.6.31-rc5-autokern1 mwait_idle

>>>      
> 
> idle=halt may improve this, mwait is slow.

I can try idle-halt on the host.  I actually assumed it would be using 
that, but I'll check.

Thanks,

-Andrew