Re: number of samples collected doesn't seem right...

[Steven L. <ren...@ho...>]

I got that from vmstat, and I make both CPU busy by running 2 programs, each 
with a closed loop like:

int i = 1;

int main(void) {
   while (1) {
      if(i == 1) i++;
      if(i == 2) i++;
      else i = 1;
   }
   return 0;
}

So is the way I calculated the expected number of samples correct??
I might be able to reboot with idle=poll to see if idle is the reason.

Thanks!!
Steven



>From: William Cohen <wc...@nc...>
>To: Steven Luk <ren...@ho...>
>CC: opr...@li...
>Subject: Re: number of samples collected doesn't seem right...
>Date: Wed, 28 Jan 2004 11:13:21 -0500
>
>Steven Luk wrote:
>>Hello, All.
>>
>>On my 2way 2.2GHz AMD64 system. The number of samples I collected for 
>>CPU_CLK_UNHALTED doesn't seem right.
>>
>>I am using count 22,000,000, and the machine is 100% busy (user CPU). So I 
>>expect about 100 samples per second per CPU, and that means 200 samples 
>>per second for my 2way. But for a 10-second interval I got only 1630 
>>samples, and for a 20-second interval I got only 2633 samples.
>>
>>Machine is a 2way AMD64 @ 2.2GHz, 2.4.21, oprofile 0.7.1
>>
>>Is the way I calculate the number of expected samples correct? Why I am 
>>not seeing about 2000 samples for 10-second interval?
>
>How did you determine that both CPU are busy? If one CPU is kept busy all 
>the time and the other CPU is idle part of the time that could explain the  
>missing 370 samples for the 10 second run and 1367 samples missing from the 
>20 second run. The CPU_CLK_UNHALTED only counts cycles when the processor 
>is unhalted. Most kernels are built to use halt in idle process to reduce 
>the amount of power consumed by the processor.
>
>-Will
>
>>
>>Thanks in advance!
>>Steven
>>
>>-------
>>Using 2.4 OProfile kernel interface.
>>Using log file /var/lib/oprofile/oprofiled.log
>>Daemon started.
>>Profiler running.
>>Signalling daemon... done
>>Killing daemon.
>>Steven Debug: It took 1 seconds to kill the Daemon
>>CPU: Hammer, speed 2191.14 MHz (estimated)
>>Counted CPU_CLK_UNHALTED events (Cycles outside of halt state) with a unit 
>>mask of 0x00 (No unit mask) count 22000000
>>CPU_CLK_UNHALT...|
>>  samples|      %|
>>------------------
>>     1628 99.8773 eatcpu
>>        1  0.0613 ld-2.2.5.so
>>        1  0.0613 libc.so.6
>>
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>>
>>
>>
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