Resolution of performance counters

[sid9559]

hello Everyone,

Is there a way to tweak with the resolution of the performance counter (event counters). Basically I am doing hotspot analysis for an algorithm and I feel that the execution time is really small that i am not able to get proper results. So, i was wondering if there is a way to reduce the threashold for the hwardware events to trigger.

regards,
siddharth

[TimP]

You may need to reduce sample after values below default, if running less than 10 seconds. This could cause VTune overheads to become significant.

[Peter_W_Intel]

Click on existing predefined analysis type (e.g. lightweight-hotspots), right-click to select "Copy from current" to create a new analysis type, you can modify "Sample After" Value.

[sid9559]

Thank you for the anwers. I am assuming that "sample after" is same as the "CPU sampling time innterval". Also, I could reduce it to 1ms. But the problem is that my algorithm has the total cpu time for 70-100 ms . Is there a way that i can analyse it in a much better way?

The problem is that my hotspot functions are consistent and I am assuming that the reason for this is the resolution.

regards,
siddharth

[Peter_W_Intel]

"Sample After" value is for lightweight-hotspots, and "CPU sample interval" is for hotspots.

If you use hotspots, please don't usesample interval to 1ms, I suggest to use 3ms. I think that you can run your critical functions several times,for example, put them into loop - in order to collect more samples.

Regards, Peter

[sid9559]

Thank you for your help. I think i will try to put my critical functions in a loop and then do some analysis.

regards,
siddharth

[Mark_D_Intel]

There are two sampling technologies used in Amplifier XE - one is based on software timers and the other is based on hardware event counters.

• The hotspots, concurrency, and locks and waits analysis types are all based on software timers. The sampling interval is set with the 'CPU sampling interval', and defaults to a 10 ms interval. One advantage of these analysis types is stack information.
• The other analysis types (lightweight hotspots, and all the others) are based on the hardware event counters. The sampling interval for these types are set with the 'Sample-After' value (can be adjusted with custom analysis types). This sampling interval can also be indirectly adjusted with the 'Duration time estimate' item in the Project Properties menu. Or -target-duration-type on the command line. It basically applies a multiplier to all the 'sample-after' values in an analysis types.).

Hopefully this should give a little background to the other recommendations in this thread.

[Bernard]

>>>Is there a way to tweak with the resolution of the performance counter (event counters>>>

The time mesurement resolution should be ~3ms.If your code executes faster you need to run it in small loop.