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VTune itself consumed 21% clocktics.

mfcking
Beginner
303 Views
Hi,
We are using the latest VTune right now to profile Linux (kernel version 2.6.13.3) network stack activities. I found sometimes VTune itself consumed about 21% total clock ticks by calling the following two functions:
prepare_to_waity()/finish_wait()
I'm just wondering why the overhead of VTune becomes so high? What is the nornal overhead when using VTune? Less than 5% clockticks?
Thanks,
L.Y.
0 Kudos
10 Replies
jeffrey-gallagher
303 Views
Curious: are you doing local data collection (using vtl or vtlec) or remote data collection (using vtserver on one system, and vtl/vtlec on another)?
cheers
jdg
mfcking
Beginner
303 Views
Hello,
I have been runningVTune rdc on Linux and performance analyzer on Windows. VTune did not always consume so much clock ticks as 21%. Most of time, the clock ticks consumed by VTune is 3~5% all contributed by prepare_to_wait()/finish_wait().I found this problem repeats when VTune is running on the 2.6.11 or higer Linux kernel version.
Thanks,
L.Y.
jeffrey-gallagher
303 Views

LY,

Double checking here only -->

after you upgraded your kernel, you wouldhave *had*to rebuild your sampling drivers pointing to the new kernel source. Either that, or, remove and reinstall the vtserver package.

You did do one of those, yes? I'm guessing you probably removed and reinstalled, but please confirm here.

jdg

Message Edited by jdgallag on 10-20-2005 04:02 PM

mfcking
Beginner
303 Views
Whenever Istart VTune (not just after rebuild the kernel), I will rebuild the sampling driver first just in case anything is changed.
L.Y.
jeffrey-gallagher
303 Views
After upgrading to a 2.6.11 or higher kernel, did you ever try a complete uninstall and reinstall of the vtserver agent? If not, would you try that and let's see if the problem stays the same, or changes, or goes away?
jeffrey-gallagher
303 Views

Hey LY

You're into new territory here. Engineering says please open a premier case on this issue at your first opportunity. They suggest:

1) please run the diagnostic script (default location /opt/intel/vtune/bin/vtqfagent) and be sure to attach the log file to your case

2) Since you're on a custom kernel, also attache the "*.config" file that was used to configure the kernel

3) Also, attach the .tb5 files where results looked OK, and where the results did NOT look OK

Cheers
jdg

Message Edited by jdgallag on 10-27-2005 12:44 PM

mfcking
Beginner
303 Views

Hello Jdg,

I did not find the diag script vtqfagent under /opt/intel/vtune/bin.

I upgraded my RDC to the latest 4.0 and still got the same problem. Two functions used by VTune (prepare_to_wait() and finish_wait()) still used 25% clock ticks.

I heard SEP is a better tool and does not cause so much overhead, is this true?

Thanks,

L.Y.

Message Edited by mfcking@yahoo.com on 12-06-2005 03:39 PM

jeffrey-gallagher
303 Views

AH yes, makes sense, you did in fact write you were using the VTune Windows GUI, and I missed that. You'd have to install the full VTune 8.0 Linux product, GUI and all, to get the /opt/intel/vtune/bin/vtqfagent application.

This forum is surely not support: have you opened your premier case yet?

jdg

Message Edited by DaveA on 12-09-2005 04:26 PM

mfcking
Beginner
303 Views

Hi Jdg,

Could you please tell me how to open a premier case?

Thanks,

L.Y.

David_A_Intel1
Employee
303 Views

LY:

If you don't already have an account at Intel Premier Support, please register for an evaluation copy of the VTune analyzer at http://www.intel.com/software/products/global/eval.htm. During your registration, make sure you opt-in to "technical support," this will create an account for you at Premier.

After logging into Premier, click on the "Submit Issue" link and follow the instructions to open a support issue.

Regards,

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