diff options
Diffstat (limited to 'block/bfq-iosched.c')
| -rw-r--r-- | block/bfq-iosched.c | 137 |
1 files changed, 42 insertions, 95 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index e68d0a4159c4..21011019f5df 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -251,55 +251,43 @@ static struct kmem_cache *bfq_pool; * When configured for computing the duration of the weight-raising * for interactive queues automatically (see the comments at the * beginning of this file), BFQ does it using the following formula: - * duration = (R / r) * T, - * where r is the peak rate of the device, and R - * and T are two reference parameters. In particular, - * R is the peak rate of the reference device (see below), and - * T is a reference time: given the systems that are likely - * to be installed on the reference device according to its speed - * class, T is about the maximum time needed, under BFQ and - * while reading two files in parallel, to load typical large - * applications on these systems (see the comments on - * max_service_from_wr below, for more details on how T is - * obtained). In practice, the slower/faster the device at hand is, - * the more/less it takes to load applications with respect to the + * duration = (ref_rate / r) * ref_wr_duration, + * where r is the peak rate of the device, and ref_rate and + * ref_wr_duration are two reference parameters. In particular, + * ref_rate is the peak rate of the reference storage device (see + * below), and ref_wr_duration is about the maximum time needed, with + * BFQ and while reading two files in parallel, to load typical large + * applications on the reference device (see the comments on + * max_service_from_wr below, for more details on how ref_wr_duration + * is obtained). In practice, the slower/faster the device at hand + * is, the more/less it takes to load applications with respect to the * reference device. Accordingly, the longer/shorter BFQ grants * weight raising to interactive applications. * - * BFQ uses four different reference pairs (R, T), depending on: - * . whether the device is rotational or non-rotational; - * . whether the device is slow, such as old or portable HDDs, as well as - * SD cards, or fast, such as newer HDDs and SSDs. + * BFQ uses two different reference pairs (ref_rate, ref_wr_duration), + * depending on whether the device is rotational or non-rotational. * - * The device's speed class is dynamically (re)detected in - * bfq_update_peak_rate() every time the estimated peak rate is updated. + * In the following definitions, ref_rate[0] and ref_wr_duration[0] + * are the reference values for a rotational device, whereas + * ref_rate[1] and ref_wr_duration[1] are the reference values for a + * non-rotational device. The reference rates are not the actual peak + * rates of the devices used as a reference, but slightly lower + * values. The reason for using slightly lower values is that the + * peak-rate estimator tends to yield slightly lower values than the + * actual peak rate (it can yield the actual peak rate only if there + * is only one process doing I/O, and the process does sequential + * I/O). * - * In the following definitions, R_slow[0]/R_fast[0] and - * T_slow[0]/T_fast[0] are the reference values for a slow/fast - * rotational device, whereas R_slow[1]/R_fast[1] and - * T_slow[1]/T_fast[1] are the reference values for a slow/fast - * non-rotational device. Finally, device_speed_thresh are the - * thresholds used to switch between speed classes. The reference - * rates are not the actual peak rates of the devices used as a - * reference, but slightly lower values. The reason for using these - * slightly lower values is that the peak-rate estimator tends to - * yield slightly lower values than the actual peak rate (it can yield - * the actual peak rate only if there is only one process doing I/O, - * and the process does sequential I/O). - * - * Both the reference peak rates and the thresholds are measured in - * sectors/usec, left-shifted by BFQ_RATE_SHIFT. + * The reference peak rates are measured in sectors/usec, left-shifted + * by BFQ_RATE_SHIFT. */ -static int R_slow[2] = {1000, 10700}; -static int R_fast[2] = {14000, 33000}; +static int ref_rate[2] = {14000, 33000}; /* - * To improve readability, a conversion function is used to initialize the - * following arrays, which entails that they can be initialized only in a - * function. + * To improve readability, a conversion function is used to initialize + * the following array, which entails that the array can be + * initialized only in a function. */ -static int T_slow[2]; -static int T_fast[2]; -static int device_speed_thresh[2]; +static int ref_wr_duration[2]; /* * BFQ uses the above-detailed, time-based weight-raising mechanism to @@ -884,7 +872,7 @@ static unsigned int bfq_wr_duration(struct bfq_data *bfqd) if (bfqd->bfq_wr_max_time > 0) return bfqd->bfq_wr_max_time; - dur = bfqd->RT_prod; + dur = bfqd->rate_dur_prod; do_div(dur, bfqd->peak_rate); /* @@ -2492,37 +2480,15 @@ static unsigned long bfq_calc_max_budget(struct bfq_data *bfqd) /* * Update parameters related to throughput and responsiveness, as a * function of the estimated peak rate. See comments on - * bfq_calc_max_budget(), and on T_slow and T_fast arrays. + * bfq_calc_max_budget(), and on the ref_wr_duration array. */ static void update_thr_responsiveness_params(struct bfq_data *bfqd) { - int dev_type = blk_queue_nonrot(bfqd->queue); - - if (bfqd->bfq_user_max_budget == 0) + if (bfqd->bfq_user_max_budget == 0) { bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd); - - if (bfqd->device_speed == BFQ_BFQD_FAST && - bfqd->peak_rate < device_speed_thresh[dev_type]) { - bfqd->device_speed = BFQ_BFQD_SLOW; - bfqd->RT_prod = R_slow[dev_type] * - T_slow[dev_type]; - } else if (bfqd->device_speed == BFQ_BFQD_SLOW && - bfqd->peak_rate > device_speed_thresh[dev_type]) { - bfqd->device_speed = BFQ_BFQD_FAST; - bfqd->RT_prod = R_fast[dev_type] * - T_fast[dev_type]; + bfq_log(bfqd, "new max_budget = %d", bfqd->bfq_max_budget); } - - bfq_log(bfqd, -"dev_type %s dev_speed_class = %s (%llu sects/sec), thresh %llu setcs/sec", - dev_type == 0 ? "ROT" : "NONROT", - bfqd->device_speed == BFQ_BFQD_FAST ? "FAST" : "SLOW", - bfqd->device_speed == BFQ_BFQD_FAST ? - (USEC_PER_SEC*(u64)R_fast[dev_type])>>BFQ_RATE_SHIFT : - (USEC_PER_SEC*(u64)R_slow[dev_type])>>BFQ_RATE_SHIFT, - (USEC_PER_SEC*(u64)device_speed_thresh[dev_type])>> - BFQ_RATE_SHIFT); } static void bfq_reset_rate_computation(struct bfq_data *bfqd, @@ -5311,14 +5277,12 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e) bfqd->wr_busy_queues = 0; /* - * Begin by assuming, optimistically, that the device is a - * high-speed one, and that its peak rate is equal to 2/3 of - * the highest reference rate. + * Begin by assuming, optimistically, that the device peak + * rate is equal to 2/3 of the highest reference rate. */ - bfqd->RT_prod = R_fast[blk_queue_nonrot(bfqd->queue)] * - T_fast[blk_queue_nonrot(bfqd->queue)]; - bfqd->peak_rate = R_fast[blk_queue_nonrot(bfqd->queue)] * 2 / 3; - bfqd->device_speed = BFQ_BFQD_FAST; + bfqd->rate_dur_prod = ref_rate[blk_queue_nonrot(bfqd->queue)] * + ref_wr_duration[blk_queue_nonrot(bfqd->queue)]; + bfqd->peak_rate = ref_rate[blk_queue_nonrot(bfqd->queue)] * 2 / 3; spin_lock_init(&bfqd->lock); @@ -5626,8 +5590,8 @@ static int __init bfq_init(void) /* * Times to load large popular applications for the typical * systems installed on the reference devices (see the - * comments before the definitions of the next two - * arrays). Actually, we use slightly slower values, as the + * comments before the definition of the next + * array). Actually, we use slightly lower values, as the * estimated peak rate tends to be smaller than the actual * peak rate. The reason for this last fact is that estimates * are computed over much shorter time intervals than the long @@ -5636,25 +5600,8 @@ static int __init bfq_init(void) * scheduler cannot rely on a peak-rate-evaluation workload to * be run for a long time. */ - T_slow[0] = msecs_to_jiffies(3500); /* actually 4 sec */ - T_slow[1] = msecs_to_jiffies(6000); /* actually 6.5 sec */ - T_fast[0] = msecs_to_jiffies(7000); /* actually 8 sec */ - T_fast[1] = msecs_to_jiffies(2500); /* actually 3 sec */ - - /* - * Thresholds that determine the switch between speed classes - * (see the comments before the definition of the array - * device_speed_thresh). These thresholds are biased towards - * transitions to the fast class. This is safer than the - * opposite bias. In fact, a wrong transition to the slow - * class results in short weight-raising periods, because the - * speed of the device then tends to be higher that the - * reference peak rate. On the opposite end, a wrong - * transition to the fast class tends to increase - * weight-raising periods, because of the opposite reason. - */ - device_speed_thresh[0] = (4 * R_slow[0]) / 3; - device_speed_thresh[1] = (4 * R_slow[1]) / 3; + ref_wr_duration[0] = msecs_to_jiffies(7000); /* actually 8 sec */ + ref_wr_duration[1] = msecs_to_jiffies(2500); /* actually 3 sec */ ret = elv_register(&iosched_bfq_mq); if (ret) |