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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
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migrate.stp
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chng_cpu.stp
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