From: Baokun Li <libaokun1@huawei.com> With a fixed inflight limit, offline workloads are still throttled even when no online workloads are running. Moreover, excessive idle inflight capacity can allow sudden offline bursts to impact online workloads, causing latency fluctuations. Introduce dynamic inflight limit adjustment, with a range from 0.1% to 100× of the configured value. The adjustment rules are: 1) When online workloads are throttled, reclaim offline budget and try to increase the total inflight limit. 2) When only offline workloads are active, increase inflight as needed without restriction. 3) If neither of the above conditions has been met since the last increase, attempt to reduce inflight to avoid excessive idle budget. Signed-off-by: Baokun Li <libaokun1@huawei.com> --- block/blk-ioinf.c | 96 +++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 88 insertions(+), 8 deletions(-) diff --git a/block/blk-ioinf.c b/block/blk-ioinf.c index c857bff375f4..848417aa5ac5 100644 --- a/block/blk-ioinf.c +++ b/block/blk-ioinf.c @@ -16,11 +16,19 @@ /* default weight for each cgroup */ #define IOINF_DFL_WEIGHT 0 -#define IOINF_MIN_INFLIGHT 30 +#define IOINF_MIN_INFLIGHT 3 #define IOINFG_MIN_INFLIGHT 1 /* default wake-up time in jiffies for backgroup job, see ioinf_timer_fn() */ #define IOINF_TIMER_PERID 500 +/* scale inflight from 1/1000 to 100 */ +enum { + MIN_SCALE = 1, /* one thousandth. */ + DFL_SCALE = 100, /* one tenth. */ + SCALE_GRAN = 1000, /* The control granularity is 1/1000. */ + MAX_SCALE = 100000, /* A hundredfold. */ +}; + /* io.inf.qos controls */ enum { INF_ENABLE, @@ -60,6 +68,8 @@ struct ioinf { struct ioinf_params params; u32 inflight; + u32 scale; + u32 old_scale; /* default time for ioinf_timer_fn */ unsigned long inf_timer_perid; @@ -265,6 +275,9 @@ static bool ioinf_inflight_cb(struct rq_wait *rqw, void *private_data) goto retry; ioinf_rqw->exhausted++; + /* wake up ioinf_timer_fn() immediately to adjust scale */ + if (inf->scale < MAX_SCALE) + timer_reduce(&inf->inf_timer, jiffies + 1); return false; } @@ -386,7 +399,9 @@ static int ioinf_stat_show(void *data, struct seq_file *m) spin_lock_irq(&inf->lock); - seq_printf(m, "inflight %u->%u\n", inf->params.inflight, inf->inflight); + seq_printf(m, "scale %u/%u inflight %u->%u\n", + inf->scale, SCALE_GRAN, + inf->params.inflight, inf->inflight); seq_printf(m, "online inflight %u/%d\n", atomic_read(&inf->online.rqw.inflight), @@ -430,6 +445,49 @@ static struct rq_qos_ops ioinf_rqos_ops = { #endif }; +static void __inflight_scale_up(struct ioinf *inf, u32 aim, bool force) +{ + u32 new_scale; + + inf->old_scale = inf->scale; + if (aim < inf->inflight || inf->scale >= MAX_SCALE) + return; + + new_scale = DIV_ROUND_UP(aim * SCALE_GRAN, inf->params.inflight); + if (new_scale <= inf->old_scale) { + if (!force) + return; + new_scale = inf->scale + 1; + } + + inf->scale = new_scale; +} + +static void inflight_scale_up(struct ioinf *inf, u32 aim) +{ + __inflight_scale_up(inf, aim, false); +} + +static void inflight_force_scale_up(struct ioinf *inf, u32 aim) +{ + __inflight_scale_up(inf, aim, true); +} + +static void inflight_scale_down(struct ioinf *inf, u32 aim) +{ + u32 new_scale; + + inf->old_scale = inf->scale; + if (inf->inflight <= IOINF_MIN_INFLIGHT || inf->old_scale >= MAX_SCALE) + return; + + new_scale = DIV_ROUND_UP(aim * SCALE_GRAN, inf->params.inflight); + if (new_scale >= inf->old_scale) + return; + + inf->scale = new_scale; +} + u32 ioinf_calc_budget(struct ioinf_rq_wait *ioinf_rqw) { u32 new_budget; @@ -487,9 +545,12 @@ static void ioinf_sample_lat(struct ioinf *inf) static void ioinf_update_inflight(struct ioinf *inf, u32 new_online, u32 new_offline) { - inf->inflight = inf->params.inflight; - if (inf->inflight < IOINF_MIN_INFLIGHT) + inf->scale = clamp(inf->scale, MIN_SCALE, MAX_SCALE); + inf->inflight = inf->params.inflight * inf->scale / SCALE_GRAN; + if (inf->inflight < IOINF_MIN_INFLIGHT) { inf->inflight = IOINF_MIN_INFLIGHT; + inf->scale = inf->inflight * SCALE_GRAN / inf->params.inflight; + } if (new_online >= inf->inflight) new_offline = min(new_offline, IOINFG_MIN_INFLIGHT); @@ -519,15 +580,32 @@ static void ioinf_timer_fn(struct timer_list *timer) online_budget = ioinf_calc_budget(online); offline_budget = ioinf_calc_budget(offline); + + if (online->exhausted) { + offline_budget = min(offline_budget, IOINFG_MIN_INFLIGHT); + inflight_force_scale_up(inf, online_budget + offline_budget); + } else if (!online_budget) { + inflight_scale_up(inf, offline_budget); + } else if (inf->old_scale < inf->scale) { + inflight_scale_down(inf, online_budget + offline->hinflight); + } + ioinf_update_inflight(inf, online_budget, offline_budget); spin_unlock_irqrestore(&inf->lock, flags); mod_timer(&inf->inf_timer, jiffies + inf->inf_timer_perid); } -static u32 ioinf_default_inflight(struct gendisk *disk) +static u32 ioinf_default_inflight(struct ioinf *inf) { - return max(disk->queue->nr_requests, IOINF_MIN_INFLIGHT); + u32 inflight = inf->params.inflight * DFL_SCALE / SCALE_GRAN; + + if (inflight < IOINF_MIN_INFLIGHT) + inflight = IOINF_MIN_INFLIGHT; + inf->scale = DIV_ROUND_UP(inflight * SCALE_GRAN, inf->params.inflight); + inf->old_scale = inf->scale; + + return inf->params.inflight * inf->scale / SCALE_GRAN; } static int blk_ioinf_init(struct gendisk *disk) @@ -546,8 +624,8 @@ static int blk_ioinf_init(struct gendisk *disk) } spin_lock_init(&inf->lock); - inf->params.inflight = ioinf_default_inflight(disk); - inf->inflight = inf->params.inflight; + inf->params.inflight = disk->queue->nr_requests; + inf->inflight = ioinf_default_inflight(inf); inf->inf_timer_perid = IOINF_TIMER_PERID; inf->offline.hinflight = IOINFG_MIN_INFLIGHT; rq_wait_init(&inf->offline.rqw); @@ -739,6 +817,8 @@ static ssize_t ioinf_qos_write(struct kernfs_open_file *of, char *input, inf->params = params; if (inf->inflight != params.inflight) { spin_lock_irq(&inf->lock); + inf->scale = SCALE_GRAN; + inf->old_scale = SCALE_GRAN; ioinf_update_inflight(inf, inf->online.hinflight, inf->offline.hinflight); spin_unlock_irq(&inf->lock); -- 2.39.2