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Ronald_G_Intel
Moderator
37 Views

can SEP co-exist with perf driver?

If a system has perf driver installed, can we also install SEP driver?  I assume Vtune first checks for SEP and uses it if it finds it.  If it can't find SEP I assume it looks for a compatible perf driver, correct?

So there should be no issues or anything special to use VTune on a system with both SEP and perf drivers?

Ron

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6 Replies
David_A_Intel1
Employee
37 Views

Correct and yes to all your questions.  The VTune Amplifier's event-based sampling driver (SEP) is the preferred collector because it has additional support, but if it is not available VTune Amplifier will attempt to use the Linux perf subsystem.

The VTune Amplifier driver supports uncore events, multiple and precise events, and events for the latest processors even on older distros.

Dmitry_P_Intel1
Employee
37 Views

Hello,

You are right, if SEP driver is installed with VTune installation then VTune will use it, if no (say you install it w/o administrative privileges)- it will try to use perf and there should not be an issue. Please note that VTune supports collection with kernel version 2.6.32 and higher.

Please note that there are some limitations with perf-based collection in VTune such as ability to collect uncore events that is used e.g. for bandwidth analysis, ability to read info from PEBS so precise events will not be actually precise and data addresses to correlate memory analysis metrics with memory objects are not available etc.

Thanks & Regards, Dmitry

Ronald_G_Intel
Moderator
37 Views

one last question:

 From either the command line or the GUI is there a way to get Vtune to inform the user which driver the collector has found and is using?  

David_A_Intel1
Employee
37 Views

Hi Ron:

Well, it doesn't tell you *which* driver it is using, only if it can't collect the data you desire with the available driver.

For example, if you attempt to use a feature which requires the VTune Amplifier driver and it is not loaded, you will receive this message:

no-sep-driver.PNG

And, from the command line:

amplxe: Warning: Context switch data cannot be collected since VTune Amplifier sampling driver is not installed.

Peter_W_Intel
Employee
37 Views

@ Ron,

I had this article for your reference.

Dmitry_P_Intel1
Employee
37 Views

Another quick way to find if VTune uses sep driver or not is to check if it is up and running on the system:

>lsmod | grep sep

should show the output with sep3_15 driver name on the machine.

Thanks & Regards, Dmitry

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