Hi folks,
I'm trying to get the time spent in IO by a process.
So, I need to know if there is any kind of implementation of this task in the kernel.
I know that there is a struct that holds some statistics (include/linux/sched.h):
#ifdef CONFIG_SCHEDSTATS
struct sched_info {
/* cumulative counters */
unsigned long
cpu_time, /* time spent on the cpu
*/
run_delay, /* time spent waiting on a
runqueue */
pcnt; /* #
of timeslices run on this cpu */
/* timestamps */
unsigned long last_arrival, /* when we last ran on a cpu */
last_queued; /* when we were last queued to run */
};
extern struct file_operations proc_schedstat_operations;
#endif
The task_struct has one sched_info field.
But it does not have any reference of IO time spent by the process.
I know that when a process sleeps it normaly uses a wait_queue. So, my
idea is create one field in the sched_info to hold the time spent in IO and
update this field value in the wait_queue manipulation functions (__add_wait_queue
and __remove_wait_queue). Or yet, update this field value in the active_task
and deactivate_task.
Using activate_task/deactivate_task is still confusing for me. activate_task
uses another function: __activate_task. And the others kernel parts use more
__activate_task than activate_task.
0 sched.c try_to_wake_up 1108 activate_task(p, rq, cpu == this_cpu);
1 sched.c __migrate_task 4182 activate_task(p, rq_dest, 0);
0 sched.c activate_task 756 __activate_task(p, rq);
1 sched.c wake_up_new_task 1237 __activate_task(p, rq);
2 sched.c wake_up_new_task 1248 __activate_task(p, rq);
3 sched.c wake_up_new_task 1265 __activate_task(p, rq);
4 sched.c sched_setscheduler 3451 __activate_task(p, rq);
5 sched.c normalize_rt_tasks 5044 __activate_task(p, task_rq(p));
So, I need to know:
1. Is there any implementation of this task (getting IO time of the processes) already done in the kernel?
2. If not, Is this idea correct? Adding a new field in the sched_info to hold IO spent and manipulate it in
functions like __add_wait_queue and __remove_wait_queue or active_task and deactivate_task.
3. How do activate_task and deactivate_task work?
Does anyone know how to help me?
--
Eduardo Bezerra Valentin
Bacharelado em Ciência da Computação - DCC - UFAM
Laboratório de VoIP - GRSD - UFAM
