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authorPietro Pedroni <pedroni.pietro.96@gmail.com>2021-06-19 16:09:45 +0200
committerJens Axboe <axboe@kernel.dk>2021-06-21 15:03:41 -0600
commit7812472f973047a886e4ed9a91d98d6627dd746f (patch)
tree4bb9e4e9e1e7b81f897f82fbbc9f2ef120dc3220 /block
parentd4f49983fa3944416c28379c35fbe10c68455ea4 (diff)
block, bfq: boost throughput by extending queue-merging times
One of the methods with which bfq boosts throughput is by merging queues. One of the merging variants in bfq is the stable merge. This mechanism is activated between two queues only if they are created within a certain maximum time T1 from each other. Merging can happen soon or be delayed. In the second case, before merging, bfq needs to evaluate a throughput-boost parameter that indicates whether the queue generates a high throughput is served alone. Merging occurs when this throughput-boost is not high enough. In particular, this parameter is evaluated and late merging may occur only after at least a time T2 from the creation of the queue. Currently T1 and T2 are set to 180ms and 200ms, respectively. In this way the merging mechanism rarely occurs because time is not enough. This results in a noticeable lowering of the overall throughput with some workloads (see the example below). This commit introduces two constants bfq_activation_stable_merging and bfq_late_stable_merging in order to increase the duration of T1 and T2. Both the stable merging activation time and the late merging time are set to 600ms. This value has been experimentally evaluated using sqlite benchmark in the Phoronix Test Suite on a HDD. The duration of the benchmark before this fix was 111.02s, while now it has reached 97.02s, a better result than that of all the other schedulers. Signed-off-by: Pietro Pedroni <pedroni.pietro.96@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Link: https://lore.kernel.org/r/20210619140948.98712-5-paolo.valente@linaro.org Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
-rw-r--r--block/bfq-iosched.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 2a5c1a660f3b..98a42ddb1760 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -364,6 +364,16 @@ static int ref_wr_duration[2];
*/
static const unsigned long max_service_from_wr = 120000;
+/*
+ * Maximum time between the creation of two queues, for stable merge
+ * to be activated (in ms)
+ */
+static const unsigned long bfq_activation_stable_merging = 600;
+/*
+ * Minimum time to be waited before evaluating delayed stable merge (in ms)
+ */
+static const unsigned long bfq_late_stable_merging = 600;
+
#define RQ_BIC(rq) icq_to_bic((rq)->elv.priv[0])
#define RQ_BFQQ(rq) ((rq)->elv.priv[1])
@@ -2711,9 +2721,9 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
if (bic->stable_merge_bfqq &&
!bfq_bfqq_just_created(bfqq) &&
time_is_before_jiffies(bfqq->split_time +
- msecs_to_jiffies(200)) &&
+ msecs_to_jiffies(bfq_late_stable_merging)) &&
time_is_before_jiffies(bfqq->creation_time +
- msecs_to_jiffies(200))) {
+ msecs_to_jiffies(bfq_late_stable_merging))) {
struct bfq_queue *stable_merge_bfqq =
bic->stable_merge_bfqq;
int proc_ref = min(bfqq_process_refs(bfqq),
@@ -5494,7 +5504,7 @@ static struct bfq_queue *bfq_do_or_sched_stable_merge(struct bfq_data *bfqd,
*/
if (!last_bfqq_created ||
time_before(last_bfqq_created->creation_time +
- bfqd->bfq_burst_interval,
+ msecs_to_jiffies(bfq_activation_stable_merging),
bfqq->creation_time) ||
bfqq->entity.parent != last_bfqq_created->entity.parent ||
bfqq->ioprio != last_bfqq_created->ioprio ||