[Barrelfish-users] Intel SCC latency measurements for MPB operations

[Konstantin Zertsekel]

Werner, thanks for the answer.
Assuming we won't use bypass mode to access the local MPB, is there any
software that tests the latency of accessing the local MPB. Our first-step
goal is to measure the latency in this simple case and see that it is 45
core clock + 8 mesh clock as is stated in the graph or at least could be
measured in clocks, not microseconds.
Can you please relate to this picture: [
https://docs.google.com/drawings/edit?id=1X-U10YjKvFQ22sdsKcNFnpHKVLyhR8_6YhJv6tiySUo&hl=en]?
Did anyone measured latency of those paths?
Thanks again, KostaZ.

On Tue, Mar 1, 2011 at 5:53 PM, Haas, Werner <werner.haas at intel.com> wrote:

>  Konstantin,
>
>
>
> I work at Intel Labs so let me try answering the RCCE-related part: The
> latency table reflects the numbers from looking at the actual hardware, i.e.
> without taking software operation into account. The RCCE round-trip times,
> however, were measured by running an actual application, i.e. they rather
> reflect the efficiency of one particular communication algorithm than
> hardware properties. I do not know the precise number but there are actually
> several MPB accesses involved in passing data via RCCE.
>
>
>
> Please also note that the bypass mode should _*not*_ be used as we have a
> hardware bug which can lead to reading incorrect data. Unfortunately this
> greatly reduces the benefit of using the on-die SRAM vs. off-die DDR3.
>
>
>
> Best regards,
>
> Werner
>
>
>
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