On 09.02.2010, at 13:27, Avi Kivity wrote:
> On 02/09/2010 01:13 PM, Alexander Graf wrote:
>> Avi Kivity wrote:
>>
>>> On 02/09/2010 01:00 PM, Alexander Graf wrote:
>>>
>>>>
>>>>> That's pretty impressive (never saw x86 with this exit rate) but it's
>>>>> more than 1000 times slower than the hardware, assuming 1 fpu IPC (and
>>>>> the processor can probably do more). An fpu intensive application
>>>>> will slow to a crawl.
>>>>>
>>>>>
>>>> Measuring a typical Gekko application, I get about 200k-250k of fpu
>>>> (incl. paired singles) instructions per second.
>>>>
>>>>
>>> Virtualized, yes? What's the rate on bare metal?
>>>
>>
>> Emulated. I can't measure anything on bare metal.
>>
>
> Well, then, the rate may be low due to virtualization overhead. Any way to compare absolute performance?
So I changed to code according to your input by making all FPU calls explicit, getting rid of all binary patching.
On the PowerStation again I'm running this code (simplified to the important instructions) using kvmctl:
li r2, 0x1234
std r2, 0(r1)
lfd f3, 0(r1)
lfd f4, 0(r1)
do_mul:
fmul f0, f3, f4
b do_mul
With the following kvm_stat output:
dec 2236 53
exits 60797802 1171403
ext_intr 379 4
halt_wakeup 0 0
inst_emu 60795247 1171344
ld 60795132 1171348
So I'm getting 1171403 fmul operations per second. And that's even with non-optimized instruction fetching. Not bad.
Alex--
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