Re: [Gems-users] IPC and Number of Instructions

[Dan Gibson <degibson@xxxxxxxx>]

The other processors are probably in a tight loop waiting for something to happen.
Candidates:
- A spinlock (waiting for a lock release)
- The OS idle loop (waiting for a scheduler invocation)

On Tue, Dec 8, 2009 at 5:34 PM, <ubaid001@xxxxxxx> wrote:

@ Dan

Can you elaborate the word "spinning" ???

Am running open MP art benchmark.

Suhail

On Dec 8 2009, Dan Gibson wrote:

>The other processors are probably spinning. Spinning tends to have great
>IPC.
>
>On Tue, Dec 8, 2009 at 2:53 PM, <ubaid001@xxxxxxx> wrote:
>
>> Hi all,
>>
>> I simulated a four core CMP system with both Opal and Ruby. In the
>> results.opal file the runtime stats for processor [0],[1],[2],[3], only
>> processor [0] executed 100 million instructions specified by
>> "opal0.sim-step 100000000", but processor [1] and [2] have more total
>> number of instructions than what I had specified.
>>
>> Even though only one core runs the required number of instructions, how
>> do
>> the other cores run so many more instructions (almost double the number
>> of
>> instructions specified). The configuration for all the processors are the
>> same. This leads to opal reporting a very high IPC for those processors.
>> e.g : P0 1.6, P1 3.96 , P2 3.97 etc.
>>
>> This is due to the fact the the number of cycles remain the same for all
>> processors.
>>
>> Am wondering if the high value of IPC reported is spurious. Can someone
>> shed more light on this?
>>
>> Suhail
>>
>>
>>
>>
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>
>
>
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