On Mon, Aug 8, 2011 at 8:25 PM, Jonathan Neuschäfer
Post by Jonathan NeuschäferPost by Rajat SharmaHi All,
What is the difference between io_schedule() and schedule(), is
io_schedule() more restrictive to shedule only I/O bound processes or
it just favours I/O bound processes. Any documentation link would be
great help.
Have you even looked at the source code?
/*
* This task is about to go to sleep on IO. Increment rq->nr_iowait so
* that process accounting knows that this is a task in IO wait state.
*/
void __sched io_schedule(void)
{
struct rq *rq = raw_rq();
delayacct_blkio_start();
atomic_inc(&rq->nr_iowait);
blk_flush_plug(current);
current->in_iowait = 1;
schedule();
current->in_iowait = 0;
atomic_dec(&rq->nr_iowait);
delayacct_blkio_end();
}
EXPORT_SYMBOL(io_schedule);
HTH,
Jonathan Neuschäfer
of course I looked at the source (obvious first step) before asking
question and further following tsk->in_iowait, it seems it is just
needed for accounting purpose.
if (tsk->in_iowait) {
se->statistics.iowait_sum += delta;
se->statistics.iowait_count++;
trace_sched_stat_iowait(tsk, delta);
}
Wanted to be sure of "is that it all about"? or I am missing something here?
-Rajat