diff options
| -rw-r--r-- | block/blk-iocost.c | 94 |
1 files changed, 69 insertions, 25 deletions
diff --git a/block/blk-iocost.c b/block/blk-iocost.c index ffcb78126ab7..9b1f94499432 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -287,9 +287,9 @@ enum { MIN_DELAY = 250, MAX_DELAY = 250 * USEC_PER_MSEC, - /* halve debts if total usage keeps staying under 25% for over 100ms */ - DEBT_BUSY_USAGE_PCT = 25, - DEBT_REDUCTION_IDLE_DUR = 100 * USEC_PER_MSEC, + /* halve debts if avg usage over 100ms is under 50% */ + DFGV_USAGE_PCT = 50, + DFGV_PERIOD = 100 * USEC_PER_MSEC, /* don't let cmds which take a very long time pin lagging for too long */ MAX_LAGGING_PERIODS = 10, @@ -433,8 +433,10 @@ struct ioc { bool weights_updated; atomic_t hweight_gen; /* for lazy hweights */ - /* the last time debt cancel condition wasn't met */ - u64 debt_busy_at; + /* debt forgivness */ + u64 dfgv_period_at; + u64 dfgv_period_rem; + u64 dfgv_usage_us_sum; u64 autop_too_fast_at; u64 autop_too_slow_at; @@ -1251,7 +1253,8 @@ static bool iocg_activate(struct ioc_gq *iocg, struct ioc_now *now) if (ioc->running == IOC_IDLE) { ioc->running = IOC_RUNNING; - ioc->debt_busy_at = now->now; + ioc->dfgv_period_at = now->now; + ioc->dfgv_period_rem = 0; ioc_start_period(ioc, now); } @@ -1990,25 +1993,66 @@ static void transfer_surpluses(struct list_head *surpluses, struct ioc_now *now) static void ioc_forgive_debts(struct ioc *ioc, u64 usage_us_sum, int nr_debtors, struct ioc_now *now) { - if (ioc->busy_level < 0 || - div64_u64(100 * usage_us_sum, now->now - ioc->period_at) >= - DEBT_BUSY_USAGE_PCT) - ioc->debt_busy_at = now->now; - - if (nr_debtors && - now->now - ioc->debt_busy_at >= DEBT_REDUCTION_IDLE_DUR) { - struct ioc_gq *iocg; - - list_for_each_entry(iocg, &ioc->active_iocgs, active_list) { - if (iocg->abs_vdebt) { - spin_lock(&iocg->waitq.lock); - iocg->abs_vdebt /= 2; - iocg->delay = 0; /* kick_waitq will recalc */ - iocg_kick_waitq(iocg, true, now); - spin_unlock(&iocg->waitq.lock); - } - } - ioc->debt_busy_at = now->now; + struct ioc_gq *iocg; + u64 dur, usage_pct, nr_cycles; + + /* if no debtor, reset the cycle */ + if (!nr_debtors) { + ioc->dfgv_period_at = now->now; + ioc->dfgv_period_rem = 0; + ioc->dfgv_usage_us_sum = 0; + return; + } + + /* + * Debtors can pass through a lot of writes choking the device and we + * don't want to be forgiving debts while the device is struggling from + * write bursts. If we're missing latency targets, consider the device + * fully utilized. + */ + if (ioc->busy_level > 0) + usage_us_sum = max_t(u64, usage_us_sum, ioc->period_us); + + ioc->dfgv_usage_us_sum += usage_us_sum; + if (time_before64(now->now, ioc->dfgv_period_at + DFGV_PERIOD)) + return; + + /* + * At least DFGV_PERIOD has passed since the last period. Calculate the + * average usage and reset the period counters. + */ + dur = now->now - ioc->dfgv_period_at; + usage_pct = div64_u64(100 * ioc->dfgv_usage_us_sum, dur); + + ioc->dfgv_period_at = now->now; + ioc->dfgv_usage_us_sum = 0; + + /* if was too busy, reset everything */ + if (usage_pct > DFGV_USAGE_PCT) { + ioc->dfgv_period_rem = 0; + return; + } + + /* + * Usage is lower than threshold. Let's forgive some debts. Debt + * forgiveness runs off of the usual ioc timer but its period usually + * doesn't match ioc's. Compensate the difference by performing the + * reduction as many times as would fit in the duration since the last + * run and carrying over the left-over duration in @ioc->dfgv_period_rem + * - if ioc period is 75% of DFGV_PERIOD, one out of three consecutive + * reductions is doubled. + */ + nr_cycles = dur + ioc->dfgv_period_rem; + ioc->dfgv_period_rem = do_div(nr_cycles, DFGV_PERIOD); + + list_for_each_entry(iocg, &ioc->active_iocgs, active_list) { + if (!iocg->abs_vdebt) + continue; + spin_lock(&iocg->waitq.lock); + iocg->abs_vdebt >>= nr_cycles; + iocg->delay = 0; /* kick_waitq will recalc */ + iocg_kick_waitq(iocg, true, now); + spin_unlock(&iocg->waitq.lock); } } |