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Mohamed_Husain
Beginner
61 Views

Load Latency PEBS

Hi,

I was measuring the  load latencies in my core i5 2450 using PEBS + load latency feature of the PMU.  The document says , latency value is measured in core cycles from micro-operation (uop) dispatch to when data is globally observable (GO). I have the following queries

1.  What is meant by 'when data is globally observable' ?
2.  The L1 latency is around 4-5 cycles.  But when I measure it using the PEBS, I get L1 hit latency values of even >100 cycles also.  ( It is a hit in dtlb/stlvb)

Can some one give a clarification

Thank you.



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1 Reply
Bernard
Black Belt
61 Views

1) I think that "Globally Observable" might be related to data beign seen and accessed by the software(registers and or memory location).