From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <1320433713.81220.YahooMailNeo@domain.hid> Date: Fri, 4 Nov 2011 12:08:33 -0700 (PDT) From: Tom Z MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="943903729-1584326518-1320433713=:81220" Subject: [Xenomai-help] 0 CPU time problem Reply-To: Tom Z List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "xenomai@xenomai.org" --943903729-1584326518-1320433713=:81220 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Hi All,=0A=0AI am trying to measure the CPU time consumed by a function foo= (), and here is how I do it:=0A=0Avoid foo(){=0A=A0=A0=A0=A0=A0=A0=A0 struc= t timespec tp1, tp2;=0A=A0=A0=A0=A0=A0=A0=A0 clock_gettime(CLOCK_PROCESS_CP= UTIME_ID, &tp);=0A=0A=A0=A0=A0 =A0=A0=A0 //Computation goes here=0A=0A=0A= =A0=A0=A0 =A0=A0=A0 clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &tp2);=0A=A0=A0= =A0 =A0=A0=A0 //The CPU time is given between the difference between tp2 an= d tp 1=0A=0A}=0A=0A=0AThe program is running on Ubuntu 10.10, and the kerne= l is 2.6.37 patched with Xenomai 2.5.6=0A=0A=0AHere is what I observed:=0A= =0A1) If foo() is running in the Linux domain (i.e., called by a regular Li= nux process), the CPU time obtained by the above method looks normal, and t= he mean CPU time of 25000 invocations of foo() is 10 ms.=0A=0A2) If foo() i= s running in the primary domain (i.e., called by a Xenomai task spawned by = rt_task_create() and rt_task_start()), then *most of the time*, the CPU tim= e also looks as normal as the result in 1), and the mean CPU time is also a= bout 10 ms. However, I also noticed that sometimes the CPU time obtained by= the above method is 0. This zero value did not appear often, and out of 25= 000 invocations of foo(), I noticed that there is only 1 invocation of foo(= ) where the CPU time is 0. BTW, the Xenomai task's priority is 99.=0A=0AWha= t causes this 0 CPU time in the primary domain? Is there something wrong wi= th my method to measure the CPU time?=0A=0AThanks,=0ATom=0A --943903729-1584326518-1320433713=:81220 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable

Hi All,

I am trying to measure the CPU time consumed by a function= foo(), and here is how I do it:

void foo(){

struct timespec tp1, tp2;

clock_gettime(CLOCK_PRO= CESS_CPUTIME_ID, &tp);

&nb= sp; //Computation= goes here

<= span class=3D"tab"> &nbs= p; clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &tp2);

&= nbsp; //The CPU time is given between the difference between tp2 and = tp 1

}

The progr= am is running on Ubuntu 10.10, and the kernel is 2.6.37 patched with Xenoma= i 2.5.6

Here is what I observed:

1) If foo() is running in the Linux domain (i.e., called by a r= egular Linux process), the CPU time obtained by the above method looks norm= al, and the mean CPU time of 25000 invocations of foo() is 10 ms.

2) If foo() is running in the primary domain (i.e., called by a Xenoma= i task spawned by rt_task_create() and rt_task_start()), then *most of the = time*, the CPU time also looks as normal as the result in 1), and the mean = CPU time is also about 10 ms. However, I also noticed that sometimes the CP= U time obtained by the above method is 0. This zero value did not appear of= ten, and out of 25000 invocations of foo(), I noticed that there is only 1 = invocation of foo() where the CPU time is 0. BTW, the Xenomai task's priority is 99.

What causes this 0 CPU time in th= e primary domain? Is there something wrong with my method to measure the CP= U time?

Thanks,

Tom

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