Re: Stap scripts to track task cpu changes

Re: Stap scripts to track task cpu changes

[Ankita Garg]

Hello William,

> Subject: Re: Stap scripts to track task cpu changes
> Date: Thursday 09 Jul 2009
> From: William Cohen <wcohen@redhat.com>
> To: Ankita Garg <ankita@in.ibm.com>, systemtap@sources.redhat.com, 
> prerna@linux.vnet.ibm.com
> 
> Ankita Garg wrote:
> > Hello folks,
> > 
> > Quite sometime back, I was faced with a situation where I needed to
> > track instances when a particular task was being migrated away from a
> > cpu. I used the following trivial script. The tid needs to be passed as
> > parameter. Sharing it, hoping it might be useful for some folks.
> 
> I would like to add these example to the systemtap examples. I have looked
> through them and made some tweaks. For both of them I formatted them not to 
> use
> tabs so they can used in documentation.
> 

Thanks for making the required formatting changes.

> For chng_cpu.stp use the appropriate probe point, scheduler.cpu_on.  Why the
> check for "tid() != 0"?
> 
> For migrate.stp The check "$1 != 0" seemed to be unneeded. Was there a reason
> for using $p->pid and kernel_string($p->comm) rather tid() and execname()?  
> The
> test is using "tid() == $1"
>

True, the checks for tid() !=0 seem unneccesary. In migrate.stp (ie in
function __migrate_task), the task being migrated need not be the
current task. Hence, using $p->pid and $p->comm, where $p is the task being
migrated.
 
> -Will

> /*    Filename: chng_cpu.stp
>  *      Author: Ankita Garg <ankita@in.ibm.com>
>  * Description: Captures information on the number of times an executable
>  * switches cpu
>  *
>  * This program is free software; you can redistribute it and/or modify
>  * it under the terms of the GNU General Public License as published by
>  * the Free Software Foundation; either version 2 of the License, or
>  * (at your option) any later version.
>  *
>  * This program is distributed in the hope that it will be useful,
>  * but WITHOUT ANY WARRANTY; without even the implied warranty of
>  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>  * GNU General Public License for more details.
>  *
>  * Copyright (C) IBM Corp. 2009.  All Rights Reserved.
>  *
>  */
> 
> global threads
> 
> probe scheduler.cpu_on
> {
>   if ((threads[tid()] != cpu()) && (tid() != 0) && (execname() == @1)) {
>     printf("thread %d (%s) context switched on %d \n",
>            tid(), execname(), cpu());
>     printf("state: %d\n", task_state(task_current()))
>     print_stack(backtrace())
>   }
>   threads[tid()] = cpu();
> }

> /*    Filename: migrate.stp
>  *      Author: Ankita Garg <ankita@in.ibm.com>
>  * Description: Captures information on the migration of a thread
>  *
>  * This program is free software; you can redistribute it and/or modify
>  * it under the terms of the GNU General Public License as published by
>  * the Free Software Foundation; either version 2 of the License, or
>  * (at your option) any later version.
>  *
>  * This program is distributed in the hope that it will be useful,
>  * but WITHOUT ANY WARRANTY; without even the implied warranty of
>  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>  * GNU General Public License for more details.
>  *
>  * Copyright (C) IBM Corp. 2009.  All Rights Reserved.
>  *
> */
> 
> probe kernel.function("__migrate_task")
> {
>   if(tid() == $1) {
>     printf ("thread %d (%s) is migrating from %d to %d \n",
>             $p->pid, kernel_string($p->comm), $src_cpu, $dest_cpu);
>   }
> }


-- 
Regards,
Ankita Garg (ankita@in.ibm.com)
Linux Technology Center
IBM India Systems & Technology Labs, 
Bangalore, India   

Re: Stap scripts to track task cpu changes

[William Cohen]

[-- Attachment #1: Type: text/plain, Size: 1860 bytes --]

Ankita Garg wrote:
> Hello William,
> 
>> Subject: Re: Stap scripts to track task cpu changes
>> Date: Thursday 09 Jul 2009
>> From: William Cohen <wcohen@redhat.com>
>> To: Ankita Garg <ankita@in.ibm.com>, systemtap@sources.redhat.com, 
>> prerna@linux.vnet.ibm.com
>>
>> Ankita Garg wrote:
>>> Hello folks,
>>>
>>> Quite sometime back, I was faced with a situation where I needed to
>>> track instances when a particular task was being migrated away from a
>>> cpu. I used the following trivial script. The tid needs to be passed as
>>> parameter. Sharing it, hoping it might be useful for some folks.
>> I would like to add these example to the systemtap examples. I have looked
>> through them and made some tweaks. For both of them I formatted them not to 
>> use
>> tabs so they can used in documentation.
>>
> 
> Thanks for making the required formatting changes.
> 
>> For chng_cpu.stp use the appropriate probe point, scheduler.cpu_on.  Why the
>> check for "tid() != 0"?
>>
>> For migrate.stp The check "$1 != 0" seemed to be unneeded. Was there a reason
>> for using $p->pid and kernel_string($p->comm) rather tid() and execname()?  
>> The
>> test is using "tid() == $1"
>>
> 
> True, the checks for tid() !=0 seem unneccesary. In migrate.stp (ie in
> function __migrate_task), the task being migrated need not be the
> current task. Hence, using $p->pid and $p->comm, where $p is the task being
> migrated.
>  
>> -Will

Hi Ankita,

A bit more tweaking on the examples. For the chng_cpu2.stp I moved the
assignment to threads associative array inside the if statement to avoid
overflowing the array. For migrate3.stp I made it take the executable name, so
that it works in a manner similar to chng_cpu2.stp. Was there multiple instances
of the same execname running one the machine or would using the execname be
sufficent for migrate.stp?

-Will

[-- Attachment #2: chng_cpu2.stp --]
[-- Type: text/plain, Size: 1034 bytes --]

/*    Filename: chng_cpu.stp
 *      Author: Ankita Garg <ankita@in.ibm.com>
 * Description: Captures information on the number of times an executable
 * switches cpu
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * Copyright (C) IBM Corp. 2009.  All Rights Reserved.
 *
 */

global threads

probe scheduler.cpu_on
{
  if ((threads[tid()] != cpu() && (execname() == @1))) {
    printf("\nthread %d (%s) context switched on cpu%d state: %d\n",
           tid(), execname(), cpu(), task_state(task_current()));
    print_stack(backtrace());
    threads[tid()] = cpu();
  }
}

[-- Attachment #3: migrate3.stp --]
[-- Type: text/plain, Size: 922 bytes --]

/*    Filename: migrate.stp
 *      Author: Ankita Garg <ankita@in.ibm.com>
 * Description: Captures information on the migration of a thread
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * Copyright (C) IBM Corp. 2009.  All Rights Reserved.
 *
*/

probe kernel.function("__migrate_task")
{
  comm = kernel_string($p->comm);
  if (comm == @1) {
    printf ("thread %d (%s) is migrating from %d to %d \n",
            $p->pid, comm, $src_cpu, $dest_cpu);
  }
}

Re: Stap scripts to track task cpu changes

[William Cohen]

[-- Attachment #1: Type: text/plain, Size: 815 bytes --]

Ankita Garg wrote:
> Hello folks,
> 
> Quite sometime back, I was faced with a situation where I needed to
> track instances when a particular task was being migrated away from a
> cpu. I used the following trivial script. The tid needs to be passed as
> parameter. Sharing it, hoping it might be useful for some folks.

I would like to add these example to the systemtap examples. I have looked
through them and made some tweaks. For both of them I formatted them not to use
tabs so they can used in documentation.

For chng_cpu.stp use the appropriate probe point, scheduler.cpu_on.  Why the
check for "tid() != 0"?

For migrate.stp The check "$1 != 0" seemed to be unneeded. Was there a reason
for using $p->pid and kernel_string($p->comm) rather tid() and execname()?  The
test is using "tid() == $1"

-Will




[-- Attachment #2: chng_cpu2.stp --]
[-- Type: text/plain, Size: 1059 bytes --]

/*    Filename: chng_cpu.stp
 *      Author: Ankita Garg <ankita@in.ibm.com>
 * Description: Captures information on the number of times an executable
 * switches cpu
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * Copyright (C) IBM Corp. 2009.  All Rights Reserved.
 *
 */

global threads

probe scheduler.cpu_on
{
  if ((threads[tid()] != cpu()) && (tid() != 0) && (execname() == @1)) {
    printf("thread %d (%s) context switched on %d \n",
           tid(), execname(), cpu());
    printf("state: %d\n", task_state(task_current()))
    print_stack(backtrace())
  }
  threads[tid()] = cpu();
}

[-- Attachment #3: migrate2.stp --]
[-- Type: text/plain, Size: 907 bytes --]

/*    Filename: migrate.stp
 *      Author: Ankita Garg <ankita@in.ibm.com>
 * Description: Captures information on the migration of a thread
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * Copyright (C) IBM Corp. 2009.  All Rights Reserved.
 *
*/

probe kernel.function("__migrate_task")
{
  if(tid() == $1) {
    printf ("thread %d (%s) is migrating from %d to %d \n",
            $p->pid, kernel_string($p->comm), $src_cpu, $dest_cpu);
  }
}

Stap scripts to track task cpu changes

[Ankita Garg]

[-- Attachment #1: Type: text/plain, Size: 2768 bytes --]

Hello folks,

Quite sometime back, I was faced with a situation where I needed to
track instances when a particular task was being migrated away from a
cpu. I used the following trivial script. The tid needs to be passed as
parameter. Sharing it, hoping it might be useful for some folks.

/*    Filename: migrate.stp
 *      Author: Ankita Garg <ankita@in.ibm.com>
 * Description: Captures information on the migration of threads 
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * © Copyright IBM Corp. 2009.  All Rights Reserved.
 *
*/

probe kernel.function("__migrate_task")
{
	if(($1 != 0 ) && (tid() == $1)) {
		printf ("thread %d (%s) is migrating from %d to %d \n", $p->pid,
				kernel_string($p->comm), $src_cpu, $dest_cpu);
	}
}


Below is a script that tracks all the cpus that a particular task ran
on. Pl note it does not track the context switches.

/*    Filename: chng_cpu.stp
 *      Author: Ankita Garg <ankita@in.ibm.com>
 * Description: Captures information on the number of times java thread
 * switches cpu
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * © Copyright IBM Corp. 2009.  All Rights Reserved.
 *
*/

global threads

probe kernel.function("finish_task_switch")
{
        if ((threads[tid()] != cpu()) && (tid() != 0) && (execname() == @1)) {
                printf("thread %d (%s) context switched on %d \n",
                                tid(), execname(), cpu());
				printf("state: %d\n", task_state(task_current()))
				print_stack(backtrace())
	}
        threads[tid()] = cpu();
}

With the new tracepoints infrastructure, the above stats could maybe be
captured in a much easier way, however, it worked well with stap as well
:-) Do let me know if you have any suggestions.


-- 
Regards,
Ankita Garg (ankita@in.ibm.com)
Linux Technology Center
IBM India Systems & Technology Labs, 
Bangalore, India   

[-- Attachment #2: migrate.stp --]
[-- Type: text/plain, Size: 910 bytes --]

/*    Filename: migrate.stp
 *      Author: Ankita Garg <ankita@in.ibm.com>
 * Description: Captures information on the migration of threads 
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * © Copyright IBM Corp. 2009.  All Rights Reserved.
 *
*/

probe kernel.function("__migrate_task")
{
	if(($1 != 0 ) && (tid() == $1)) {
		printf ("thread %d (%s) is migrating from %d to %d \n", $p->pid,
				kernel_string($p->comm), $src_cpu, $dest_cpu);
	}
}

[-- Attachment #3: chng_cpu.stp --]
[-- Type: text/plain, Size: 1120 bytes --]

/*    Filename: chng_cpu.stp
 *      Author: Ankita Garg <ankita@in.ibm.com>
 * Description: Captures information on the number of times java thread
 * switches cpu
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * © Copyright IBM Corp. 2009.  All Rights Reserved.
 *
*/

global threads

probe kernel.function("finish_task_switch")
{
        if ((threads[tid()] != cpu()) && (tid() != 0) && (execname() == @1)) {
                printf("thread %d (%s) context switched on %d \n",
                                tid(), execname(), cpu());
				printf("state: %d\n", task_state(task_current()))
				print_stack(backtrace())
	}
        threads[tid()] = cpu();
}