C-States and advanced hotspots

Hagen_G_ · ‎10-19-2014

Hi,

when I prepare an advanced hotspots analysis VTune always show me the warning shown in the attached image "141020 c-states warning.PNG".

As I often see "paused" sections in my analysis results it would be nice to check if this C-states problem effectively affects analyses done on my system. I have a Dell T7500. This is an older machine containing a Xeon X5650. When I look at the bios I see no option matching the one mentioned in the VTune warning ("Cn(ACPI Cn) report to OS". The "simplified" Dell bios options only allow me to adjust some more basic ACPI settings such as "ACPI" or "RAID On".

When using the Dell CCTK tool I can read out some more detailed settings, but even in those I don't find the problematic option mentioned in the VTune warning (see attached image "141020 dell acpi.PNG").

Can someone point me to more details about the "Cn(ACPI Cn) report to OS" option, what it does, and where I can possibly find it in a Dell bios?

Regards, Hagen

Peter_W_Intel · ‎10-20-2014

I saw such warning message from Intel(R) Xeon 56-serial processors, when using advanced-hotspots or other event-based sampling. I didn't see any system hang even one time, you can ignore this warning message.

David_A_Intel1 · ‎10-20-2014

If you are able to collect data, then you don't have to worry about the message or BIOS settings. If your system hangs when you try to collect, then you need to heed the warning and change your BIOS settings.

As far as the "paused time", please see this article.

Hagen_G_ · ‎10-21-2014

Thanks, very interesting.

Just another comment: I could reduce the pausing artefacts on my system quite a lot by storing the VTune project on a local disk instead of on a network drive.

Still some pausing remains, but according to what you say I will simply ignore it.

Regards, Hagen

David_A_Intel1 · ‎10-21-2014

Yes, we always recommend you store the project and results on a local disk. Any network communication required to read and write data will slow the performance of the results collection and display. Thanks for bringing that up!