Analyzers
Talk to fellow users of Intel Analyzer tools (Intel VTune™ Profiler, Intel Advisor)
4994 Discussions

Weird profiling result of mwait_idle() function by VTune.

mfcking
Beginner
357 Views
Hello,
I used VTune 3.0 to profile the Linuxnetwork stack activities(RHEL 4.0 with 2.6 kernel). The NIC driveri used is 6.0.60 forIntelgigabit dual-port NIC.
I found the total clock ticks usedby the mwait_idle() function is unbelieveably as high as 50% of total clock ticks when I enabled hyper-threading for a dual Xeon processor platforms and the CPI for this mwait_idle() is about 4000. I did the same testing on a single Xeon processor with hyper threading enabled. The mwait_idle() only used 5% of total clock ticks and the CPI is about 1000.
I understand why CPI of mwait is so high (run as fewer instructions as possible).
But mwait_idle() should not be take half of clock ticks? If so, this means there is alwayshalf ofCPUsbeing idle for this dual-cpu platform? Right?
Anyonehas any clueabout this?
Thanks,
m.f.c.

Message Edited by mfcking@yahoo.com on 08-17-2005 05:10 PM

0 Kudos
1 Reply
colin
Beginner
357 Views
Hi,

That would happen if you were running just one single threaded process.

Try running top. It should show how many CPUs are active and how many processes are working.

Colin
0 Kudos
Reply