[PATCH V2 07/22] block, cfq: get rid of workload type
From: Paolo Valente
Date: Mon Aug 08 2016 - 07:20:33 EST
From: Arianna Avanzini <avanzini.arianna@xxxxxxxxx>
CFQ selects the queue to serve also according to the type of workload
it is part of. This kind of heuristic has no match in BFQ, where a
high throughput, and, at the same time, provable service guarantees
are provided through a unified overall scheduling policy.
Signed-off-by: Arianna Avanzini <avanzini.arianna@xxxxxxxxx>
Signed-off-by: Paolo Valente <paolo.valente@xxxxxxxxxx>
---
block/cfq-iosched.c | 131 +++++++++++-----------------------------------------
1 file changed, 26 insertions(+), 105 deletions(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 5e0daaf..329ed2b 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -155,15 +155,6 @@ enum wl_class_t {
CFQ_PRIO_NR,
};
-/*
- * Second index in the service_trees.
- */
-enum wl_type_t {
- ASYNC_WORKLOAD = 0,
- SYNC_NOIDLE_WORKLOAD = 1,
- SYNC_WORKLOAD = 2
-};
-
struct cfq_io_cq {
struct io_cq icq; /* must be the first member */
struct cfq_queue *cfqq[2];
@@ -179,20 +170,16 @@ struct cfq_data {
/*
* rr lists of queues with requests. We maintain service trees for
- * RT and BE classes. These trees are subdivided in subclasses
- * of SYNC, SYNC_NOIDLE and ASYNC based on workload type. For IDLE
- * class there is no subclassification and all the cfq queues go on
- * a single tree service_tree_idle.
+ * RT and BE classes.
* Counts are embedded in the cfq_rb_root
*/
- struct cfq_rb_root service_trees[2][3];
+ struct cfq_rb_root service_trees[2];
struct cfq_rb_root service_tree_idle;
/*
* The priority currently being served
*/
enum wl_class_t serving_wl_class;
- enum wl_type_t serving_wl_type;
u64 workload_expires;
unsigned int busy_queues;
@@ -292,9 +279,8 @@ CFQ_CFQQ_FNS(wait_busy);
#undef CFQ_CFQQ_FNS
#define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
- blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c " fmt, (cfqq)->pid, \
+ blk_add_trace_msg((cfqd)->queue, "cfq%d%c " fmt, (cfqq)->pid, \
cfq_cfqq_sync((cfqq)) ? 'S' : 'A', \
- cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
##args)
#define cfq_log(cfqd, fmt, args...) \
@@ -303,12 +289,12 @@ CFQ_CFQQ_FNS(wait_busy);
/* Traverses through cfq service trees */
#define for_each_st(cfqd, i, j, st) \
for (i = 0; i <= IDLE_WORKLOAD; i++) \
- for (j = 0, st = i < IDLE_WORKLOAD ? &cfqd->service_trees[i][j]\
+ for (j = 0, st = i < IDLE_WORKLOAD ? &cfqd->service_trees[i]\
: &cfqd->service_tree_idle; \
- (i < IDLE_WORKLOAD && j <= SYNC_WORKLOAD) || \
- (i == IDLE_WORKLOAD && j == 0); \
- j++, st = i < IDLE_WORKLOAD ? \
- &cfqd->service_trees[i][j] : NULL) \
+ (i < IDLE_WORKLOAD) || \
+ (i == IDLE_WORKLOAD); \
+ st = i < IDLE_WORKLOAD ? \
+ &cfqd->service_trees[i] : NULL) \
static inline bool cfq_io_thinktime_big(struct cfq_data *cfqd,
struct cfq_ttime *ttime)
@@ -329,33 +315,6 @@ static inline enum wl_class_t cfqq_class(struct cfq_queue *cfqq)
return BE_WORKLOAD;
}
-
-static enum wl_type_t cfqq_type(struct cfq_queue *cfqq)
-{
- if (!cfq_cfqq_sync(cfqq))
- return ASYNC_WORKLOAD;
- if (!cfq_cfqq_idle_window(cfqq))
- return SYNC_NOIDLE_WORKLOAD;
- return SYNC_WORKLOAD;
-}
-
-static inline int cfq_busy_queues_wl(enum wl_class_t wl_class,
- struct cfq_data *cfqd)
-{
- if (wl_class == IDLE_WORKLOAD)
- return cfqd->service_tree_idle.count;
-
- return cfqd->service_trees[wl_class][ASYNC_WORKLOAD].count +
- cfqd->service_trees[wl_class][SYNC_NOIDLE_WORKLOAD].count +
- cfqd->service_trees[wl_class][SYNC_WORKLOAD].count;
-}
-
-static inline int cfq_busy_async_queues(struct cfq_data *cfqd)
-{
- return cfqd->service_trees[RT_WORKLOAD][ASYNC_WORKLOAD].count +
- cfqd->service_trees[BE_WORKLOAD][ASYNC_WORKLOAD].count;
-}
-
static void cfq_dispatch_insert(struct request_queue *, struct request *);
static struct cfq_queue *cfq_get_queue(struct cfq_data *cfqd, bool is_sync,
struct cfq_io_cq *cic, struct bio *bio);
@@ -689,7 +648,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
int new_cfqq = 1;
u64 now = ktime_get_ns();
- st = &cfqd->service_trees[cfqq_class(cfqq)][cfqq_type(cfqq)];
+ st = &cfqd->service_trees[cfqq_class(cfqq)];
if (cfq_class_idle(cfqq)) {
rb_key = CFQ_IDLE_DELAY;
parent = rb_last(&st->rb);
@@ -1017,8 +976,8 @@ static void __cfq_set_active_queue(struct cfq_data *cfqd,
struct cfq_queue *cfqq)
{
if (cfqq) {
- cfq_log_cfqq(cfqd, cfqq, "set_active wl_class:%d wl_type:%d",
- cfqd->serving_wl_class, cfqd->serving_wl_type);
+ cfq_log_cfqq(cfqd, cfqq, "set_active wl_class:%d",
+ cfqd->serving_wl_class);
cfqq->slice_start = 0;
cfqq->dispatch_start = ktime_get_ns();
cfqq->allocated_slice = 0;
@@ -1091,9 +1050,7 @@ static inline void cfq_slice_expired(struct cfq_data *cfqd, bool timed_out)
*/
static struct cfq_queue *cfq_get_next_queue(struct cfq_data *cfqd)
{
- struct cfq_rb_root *st =
- &cfqd->service_trees[cfqd->serving_wl_class]
- [cfqd->serving_wl_type];
+ struct cfq_rb_root *st = &cfqd->service_trees[cfqd->serving_wl_class];
if (!cfqd->rq_queued)
return NULL;
@@ -1221,6 +1178,15 @@ static void cfq_arm_slice_timer(struct cfq_data *cfqd)
cfq_log_cfqq(cfqd, cfqq, "arm_idle: %llu", sl);
}
+static inline int cfq_busy_queues_wl(enum wl_class_t wl_class,
+ struct cfq_data *cfqd)
+{
+ if (wl_class == IDLE_WORKLOAD)
+ return cfqd->service_tree_idle.count;
+
+ return cfqd->service_trees[wl_class].count;
+}
+
/*
* Move request from internal lists to the request queue dispatch list.
*/
@@ -1273,29 +1239,6 @@ cfq_prio_to_maxrq(struct cfq_data *cfqd, struct cfq_queue *cfqq)
return 2 * base_rq * (IOPRIO_BE_NR - cfqq->ioprio);
}
-static enum wl_type_t cfq_choose_wl_type(struct cfq_data *cfqd,
- enum wl_class_t wl_class)
-{
- struct cfq_queue *queue;
- int i;
- bool key_valid = false;
- u64 lowest_key = 0;
- enum wl_type_t cur_best = SYNC_NOIDLE_WORKLOAD;
-
- for (i = 0; i <= SYNC_WORKLOAD; ++i) {
- /* select the one with lowest rb_key */
- queue = cfq_rb_first(&cfqd->service_trees[wl_class][i]);
- if (queue &&
- (!key_valid || queue->rb_key < lowest_key)) {
- lowest_key = queue->rb_key;
- cur_best = i;
- key_valid = true;
- }
- }
-
- return cur_best;
-}
-
static void
choose_wl_class_and_type(struct cfq_data *cfqd)
{
@@ -1319,13 +1262,7 @@ choose_wl_class_and_type(struct cfq_data *cfqd)
if (original_class != cfqd->serving_wl_class)
goto new_workload;
- /*
- * For RT and BE, we have to choose also the type
- * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
- * expiration time
- */
- st = &cfqd->service_trees[cfqd->serving_wl_class]
- [cfqd->serving_wl_type];
+ st = &cfqd->service_trees[cfqd->serving_wl_class];
count = st->count;
/*
@@ -1335,26 +1272,11 @@ choose_wl_class_and_type(struct cfq_data *cfqd)
return;
new_workload:
- /* otherwise select new workload type */
- cfqd->serving_wl_type = cfq_choose_wl_type(cfqd,
- cfqd->serving_wl_class);
- st = &cfqd->service_trees[cfqd->serving_wl_class]
- [cfqd->serving_wl_type];
+ st = &cfqd->service_trees[cfqd->serving_wl_class];
count = st->count;
- if (cfqd->serving_wl_type == ASYNC_WORKLOAD) {
- slice = cfqd->cfq_target_latency *
- cfq_busy_async_queues(cfqd);
- slice = div_u64(slice, cfqd->busy_queues);
-
- /* async workload slice is scaled down according to
- * the sync/async slice ratio. */
- slice = div64_u64(slice*cfqd->cfq_slice[0], cfqd->cfq_slice[1]);
- } else
- /* sync workload slice is 2 * cfq_slice_idle */
- slice = 2 * cfqd->cfq_slice_idle;
-
- slice = max_t(u64, slice, CFQ_MIN_TT);
+ /* sync workload slice is at least 2 * cfq_slice_idle */
+ slice = max_t(u64, 2 * cfqd->cfq_slice_idle, CFQ_MIN_TT);
cfq_log(cfqd, "workload slice:%llu", slice);
cfqd->workload_expires = now + slice;
}
@@ -2102,8 +2024,7 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
if (cfq_cfqq_on_rr(cfqq))
st = cfqq->service_tree;
else
- st = &cfqd->service_trees[cfqq_class(cfqq)]
- [cfqq_type(cfqq)];
+ st = &cfqd->service_trees[cfqq_class(cfqq)];
st->ttime.last_end_request = now;
/*
--
1.9.1