On 06/16/2011 09:08 AM, Peter Zijlstra wrote:
> On Thu, 2011-06-16 at 08:08 -0600, David Ahern wrote:
>> Command:
>> perf stat -e instructions openssl speed aes
>>
>> Guest:
>> 135,522,189,056 instructions # 0.00 insns per cycle
>>
>>
>> Host:
>> 346,082,922,185 instructions # 0.00 insns per cycle
>
> How does: perf stat -e instructions:u openssl speed aes, compare?
I think the problem is that perf stat in the guest introduces
significant overhead. I ran perf-record in the host on the VM pid while
running 'perf stat openssl speed aes' in the guest.
perf-report on that data shows:
18.06% 9226 [k] arch_local_irq_enable
|
|--99.77%-- kvm_arch_vcpu_ioctl_run
| kvm_vcpu_ioctl
| do_vfs_ioctl
| sys_ioctl
| system_call_fastpath
| __GI___ioctl
| 0x10100000002
--0.23%-- [...]
and then perf-annotate on kvm_arch_vcpu_ioctl_run shows
: vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
21.47 : 1613a: 48 8b 3b mov (%rbx),%rdi
David
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