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lina_c_
Beginner
112 Views

How to get cpu install

I want get 'cpu stall' using vtune.which event should i use?How to use? I have found two events.

UOPS_RETIRED.STALLED_CYCLES?

UOPS_RETIRED.STALLED?

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6 Replies
Bernard
Black Belt
112 Views

I would rather go with the full analysis of back end and front end pipeline stalls.There you have already calculated breakdown of various stalled uops at various stages of pipelined execution.

lina_c_
Beginner
112 Views

back end and front end pipeline stalls? what are they?

I just want to get cpu install for memory access

Peter_W_Intel
Employee
112 Views

First at all, you may read book <Intel® 64 and IA-32 Architectures Optimization Reference Manual> if you have time (which can be download from Intel website). For saving your time, you also can read <Tuning Guides and Performance Analysis Papers> for different processor type.

iliyapolak is right that you have to consider stalls from the front end and back end. For example, stall from instruction fetching due to Instruction cache miss, IDQ is buff, branch misprediction, ROB is full, Resource Allocation Table is not usable to Reservation Station, and RS can not dispatch uops to execution unit since Port 1-n are busy. At the back end, maybe Load/Store buffer will cause delay as well as Data Cache Miss (also TLB miss), nonalignment data access, 4K-aliasing, etc . Also, uops retirement (in ROB) might cause delay (piror instruction is retired), etc.

To know which events name supported in your platform will cause stall, you can use "amplxe-runss -event-list | grep STALL" . However some events name without "STALL", for example L2_MISS also will cause penalty - you need to read guideline or optimization user manual.

Regards, Peter 

Bernard
Black Belt
112 Views

@lina

Peter explained that pretty well.

Bernard
Black Belt
112 Views

I would like also add  that SIMD floating point stack(fadd and fmul) units can be stalled  while executing  interdependent FP code for example on Port 0.

Bernard
Black Belt
112 Views

I would like also add  that SIMD floating point stack(fadd and fmul) units can be stalled  while executing  interdependent FP code for example on Port 0.

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