Profiling a single threaded single process running on a single CPU with General Exploration

Prasanth_G_ · ‎08-19-2016

I am trying to profile a process on linux running on a single CPU on a Broadwell (model name : Intel(R) Xeon(R) CPU D-1540 @ 2.00GHz) and getting a CPI rate of 2.828 with default Vtune config. With more samples (reducing the sample interval), I see it bumps up to 3.148. While I understand one or two delay functions in "Bottom-up" chart that are affecting the CPI rate, what I do not understand is "vmlinux" showing a CPI rate of 1.588. According to system config, CPU that I am running is dedicated to the process and any actions of linux kernel should be performed on a different CPU. Does CPI 1.588 above say this is not happening ? Any help is greatly appreciated. Any other suggestions/comments based on the results and Vtune-config pasted below?

Vtune config on General Exploration:

1. Attach to a process with ssh session.

2. Automatically stop after 60 secs.

3. Analyse child processes.

4. Under 1 minute of duration estimate

5. Collection data: 0

6. Slow frames: 40, Fast frames: 100 (default values)

7. CPU mask: 11

RESULTS:

With defaults:

Elapsed Time:   60.059s
Clockticks:   151,600,000
Instructions Retired:   53,600,000
CPI Rate:   2.828
MUX Reliability:   0.948
Front-End Bound:   0.191
Front-End Latency:   0.106
ICache Misses:   0.026
ITLB Overhead:   0.009
Branch Resteers:   0.047
DSB Switches:   0.000
Length Changing Prefixes:   0.000
MS Switches:   0.106
Front-End Bandwidth:   0.086
Front-End Bandwidth DSB:   0.026
Front-End Bandwidth MITE:   0.237
Front-End Bandwidth LSD:   0.000
Bad Speculation:   0.046
Back-End Bound:   0.584
Memory Bound:   0.217
L1 Bound:   0.237
L2 Bound:   0.000
L3 Bound:   0.000
DRAM Bound:   0.211
Store Bound:   0.000
Core Bound:   0.367
Divider:   0.000
Port Utilization:   0.923
Cycles of 0 Ports Utilized:   0.633
Cycles of 1 Port Utilized:   0.290
Cycles of 2 Ports Utilized:   0.053
Cycles of 3+ Ports Utilized:   0.079
Retiring:   0.178
General Retirement:   0.113
Microcode Sequencer:   0.065
Assists:   0.000
Total Thread Count:   5
Paused Time:   0s

With Sampling Interval event-config=CPU_CLK_UNHALTED.THREAD:sa=200000,INST_RETIRED.ANY:sa=200000 as suggested in another recent post.

Elapsed Time:   60.001s
Clockticks:   1,454,600,000
Instructions Retired:   462,000,000
CPI Rate:   3.148
MUX Reliability:   0.984
Front-End Bound:   0.067
Front-End Latency:   0.063
ICache Misses:   0.019
ITLB Overhead:   0.003
Branch Resteers:   0.025
DSB Switches:   0.000
Length Changing Prefixes:   0.000
MS Switches:   0.121
Front-End Bandwidth:   0.004
Front-End Bandwidth DSB:   0.000
Front-End Bandwidth MITE:   0.179
Front-End Bandwidth LSD:   0.000
Bad Speculation:   0.009
Back-End Bound:   0.769
Memory Bound:   0.365
L1 Bound:   0.294
L2 Bound:   0.000
L3 Bound:   0.234
DRAM Bound:   0.000
Store Bound:   0.000
Core Bound:   0.404
Divider:   0.000
Port Utilization:   0.660
Cycles of 0 Ports Utilized:   0.415
Cycles of 1 Port Utilized:   0.242
Cycles of 2 Ports Utilized:   0.110
Cycles of 3+ Ports Utilized:   0.049
Retiring:   0.155
General Retirement:   0.056
Microcode Sequencer:   0.099
Assists:   0.000
Total Thread Count:   5
Paused Time:   0s

Dmitry_R_Intel1 · ‎08-22-2016

Hello Prasanth,

When a process does say system call it will be done in the context of this process. Most likely this is what happening in your case.