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Commit 2e48a530 authored by Tejun Heo's avatar Tejun Heo
Browse files

blk-throttle: make throtl_pending_timer_fn() ready for hierarchy 



throtl_pending_timer_fn() currently assumes that the parent_sq is the
top level one and the bio's dispatched are ready to be issued;
however, this assumption will be wrong with proper hierarchy support.
This patch makes the following changes to make
throtl_pending_timer_fn() ready for hiearchy.

* If the parent_sq isn't the top-level one, update the parent
  throtl_grp's dispatch time and schedule the next dispatch as
  necessary.  If the parent's dispatch time is now, repeat the
  function for the parent throtl_grp.

* If the parent_sq is the top-level one, kick issue work_item as
  before.

* The debug message printed by throtl_log() now prints out the
  service_queue's nr_queued[] instead of the total nr_queued as the
  latter becomes uninteresting and misleading with hierarchical
  dispatch.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarVivek Goyal <vgoyal@redhat.com>
parent 6bc9c2b4

block/blk-throttle.c

+33 −7
Original line number Diff line number Diff line
@@ -952,23 +952,33 @@ static int throtl_select_dispatch(struct throtl_service_queue *parent_sq) 
 * This timer is armed when a child throtl_grp with active bio's become

 * pending and queued on the service_queue's pending_tree and expires when

 * the first child throtl_grp should be dispatched.  This function

 * dispatches bio's from the children throtl_grps and kicks

 * throtl_data->dispatch_work if there are bio's ready to be issued.

 * dispatches bio's from the children throtl_grps to the parent

 * service_queue.

 *

 * If the parent's parent is another throtl_grp, dispatching is propagated

 * by either arming its pending_timer or repeating dispatch directly.  If

 * the top-level service_tree is reached, throtl_data->dispatch_work is

 * kicked so that the ready bio's are issued.

 */

static void throtl_pending_timer_fn(unsigned long arg)

{

	struct throtl_service_queue *sq = (void *)arg;

	struct throtl_grp *tg = sq_to_tg(sq);

	struct throtl_data *td = sq_to_td(sq);

	struct request_queue *q = td->queue;

	bool dispatched = false;

	struct throtl_service_queue *parent_sq;

	bool dispatched;

	int ret;



	spin_lock_irq(q->queue_lock);

again:

	parent_sq = sq->parent_sq;

	dispatched = false;



	while (true) {

		throtl_log(sq, "dispatch nr_queued=%u read=%u write=%u",

			   td->nr_queued[READ] + td->nr_queued[WRITE],

			   td->nr_queued[READ], td->nr_queued[WRITE]);

			   sq->nr_queued[READ] + sq->nr_queued[WRITE],

			   sq->nr_queued[READ], sq->nr_queued[WRITE]);



		ret = throtl_select_dispatch(sq);

		if (ret) {
@@ -985,9 +995,25 @@ static void throtl_pending_timer_fn(unsigned long arg) 
		spin_lock_irq(q->queue_lock);

	}



	if (dispatched)

		queue_work(kthrotld_workqueue, &td->dispatch_work);

	if (!dispatched)

		goto out_unlock;



	if (parent_sq) {

		/* @parent_sq is another throl_grp, propagate dispatch */

		if (tg->flags & THROTL_TG_WAS_EMPTY) {

			tg_update_disptime(tg);

			if (!throtl_schedule_next_dispatch(parent_sq, false)) {

				/* window is already open, repeat dispatching */

				sq = parent_sq;

				tg = sq_to_tg(sq);

				goto again;

			}

		}

	} else {

		/* reached the top-level, queue issueing */

		queue_work(kthrotld_workqueue, &td->dispatch_work);

	}

out_unlock:

	spin_unlock_irq(q->queue_lock);

}