iocost: consider iocgs with active delays for debt forgiveness (bec02dbb) · Commits · 戴 / test

An iocg may have 0 debt but non-zero delay. The current debt forgiveness logic doesn't act on such iocgs. This can lead to unexpected behaviors - an iocg with a little bit of debt will have its delay canceled through debt forgiveness but one w/o any debt but active delay will have to wait out until its delay decays out. This patch updates the debt handling logic so that it treats delays the same as debts. If either debt or delay is active, debt forgiveness logic kicks in and acts on both the same way. Also, avoid turning the debt and delay directly to zero as that can confuse state transitions. Signed-off-by:

Tejun Heo <tj@kernel.org> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

block/blk-iocost.c

+7 −4

Original line number	Diff line number	Diff line
		@@ -2048,7 +2048,7 @@ static void ioc_forgive_debts(struct ioc *ioc, u64 usage_us_sum, int nr_debtors,
		list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {
		u64 __maybe_unused old_debt, __maybe_unused old_delay;

		if (!iocg->abs_vdebt)
		if (!iocg->abs_vdebt && !iocg->delay)
		continue;

		spin_lock(&iocg->waitq.lock);
		@@ -2056,8 +2056,11 @@ static void ioc_forgive_debts(struct ioc *ioc, u64 usage_us_sum, int nr_debtors,
		old_debt = iocg->abs_vdebt;
		old_delay = iocg->delay;

		iocg->abs_vdebt >>= nr_cycles;
		iocg->delay = 0; /* kick_waitq will recalc */
		if (iocg->abs_vdebt)
		iocg->abs_vdebt = iocg->abs_vdebt >> nr_cycles ?: 1;
		if (iocg->delay)
		iocg->delay = iocg->delay >> nr_cycles ?: 1;

		iocg_kick_waitq(iocg, true, now);

		TRACE_IOCG_PATH(iocg_forgive_debt, iocg, now, usage_pct,
		@@ -2129,7 +2132,7 @@ static void ioc_timer_fn(struct timer_list *timer)
		iocg->delay) {
		/* might be oversleeping vtime / hweight changes, kick */
		iocg_kick_waitq(iocg, true, &now);
		if (iocg->abs_vdebt)
		if (iocg->abs_vdebt \|\| iocg->delay)
		nr_debtors++;
		} else if (iocg_is_idle(iocg)) {
		/* no waiter and idle, deactivate */

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