This systemtap script will get the execution path when it reaches
set_task_cpu() in kernel 3.19.
set_task_cpu() is where perf sw cpu migration counter is updated.
#!/usr/bin/stap
probe kernel.function("set_task_cpu").call
{
// running process
// pr_name = execname()
// pr_pid = pid()
// task to be migrated
_pid = task_pid($p)
_name = task_execname($p)
_migr = $p->se->nr_migrations
_ocpu = task_cpu($p)
_ncpu = $new_cpu
if (_ocpu != _ncpu) {
printf("task %d (%s) (migr=%d) from (cpu=%d) to (cpu = %d)\n", _pid ,
_name , _migr, _ocpu, _ncpu)
print_backtrace()
}
}
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https://bugs.launchpad.net/bugs/1575407
Title:
Trusty + 3.19 (lts-vivid) PERF wrong cpu-migration counter
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