[PATCH 1/8] blk-throttle: convert wait routines to return jiffies to wait
From: Vivek Goyal
Date: Fri Jun 03 2011 - 17:07:46 EST
Currently we return jiffies to wait for in a function parameter.
A cleaner way would be to return it as return value. Value 0 would mean
that there is no need to wait and anything > 0 means number of jiffies
to wait before bio can be dispatched.
Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
block/blk-throttle.c | 72 +++++++++++++++++++++-----------------------------
1 files changed, 30 insertions(+), 42 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index a62be8d..791116e 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -590,8 +590,8 @@ throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw)
tg->slice_start[rw], tg->slice_end[rw], jiffies);
}
-static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
- struct bio *bio, unsigned long *wait)
+static unsigned long tg_wait_iops_limit(struct throtl_data *td,
+ struct throtl_grp *tg, struct bio *bio)
{
bool rw = bio_data_dir(bio);
unsigned int io_allowed;
@@ -621,11 +621,8 @@ static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
else
io_allowed = tmp;
- if (tg->io_disp[rw] + 1 <= io_allowed) {
- if (wait)
- *wait = 0;
- return 1;
- }
+ if (tg->io_disp[rw] + 1 <= io_allowed)
+ return 0;
/* Calc approx time to dispatch */
jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1;
@@ -635,13 +632,15 @@ static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg,
else
jiffy_wait = 1;
- if (wait)
- *wait = jiffy_wait;
- return 0;
+ return jiffy_wait;
}
-static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,
- struct bio *bio, unsigned long *wait)
+/*
+ * Returns number of jiffies to wait to before IO can be dispatched according
+ * to bps limit.
+ */
+static unsigned long tg_wait_bps_limit(struct throtl_data *td,
+ struct throtl_grp *tg, struct bio *bio)
{
bool rw = bio_data_dir(bio);
u64 bytes_allowed, extra_bytes, tmp;
@@ -659,11 +658,8 @@ static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,
do_div(tmp, HZ);
bytes_allowed = tmp;
- if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) {
- if (wait)
- *wait = 0;
- return 1;
- }
+ if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed)
+ return 0;
/* Calc approx time to dispatch */
extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed;
@@ -677,9 +673,8 @@ static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg,
* up we did. Add that time also.
*/
jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed);
- if (wait)
- *wait = jiffy_wait;
- return 0;
+
+ return jiffy_wait;
}
static bool tg_no_rule_group(struct throtl_grp *tg, bool rw) {
@@ -691,9 +686,12 @@ static bool tg_no_rule_group(struct throtl_grp *tg, bool rw) {
/*
* Returns whether one can dispatch a bio or not. Also returns approx number
* of jiffies to wait before this bio is with-in IO rate and can be dispatched
+ *
+ * Retruns the number of jiffies one needs to wait before IO can be dispatched.
+ * 0 means, IO can be dispatched now.
*/
-static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
- struct bio *bio, unsigned long *wait)
+static unsigned long
+tg_wait_dispatch(struct throtl_data *td, struct throtl_grp *tg, struct bio *bio)
{
bool rw = bio_data_dir(bio);
unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0;
@@ -707,11 +705,8 @@ static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw]));
/* If tg->bps = -1, then BW is unlimited */
- if (tg->bps[rw] == -1 && tg->iops[rw] == -1) {
- if (wait)
- *wait = 0;
- return 1;
- }
+ if (tg->bps[rw] == -1 && tg->iops[rw] == -1)
+ return 0;
/*
* If previous slice expired, start a new one otherwise renew/extend
@@ -725,22 +720,15 @@ static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg,
throtl_extend_slice(td, tg, rw, jiffies + throtl_slice);
}
- if (tg_with_in_bps_limit(td, tg, bio, &bps_wait)
- && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) {
- if (wait)
- *wait = 0;
- return 1;
- }
+ bps_wait = tg_wait_bps_limit(td, tg, bio);
+ iops_wait = tg_wait_iops_limit(td, tg, bio);
max_wait = max(bps_wait, iops_wait);
- if (wait)
- *wait = max_wait;
-
if (time_before(tg->slice_end[rw], jiffies + max_wait))
throtl_extend_slice(td, tg, rw, jiffies + max_wait);
- return 0;
+ return max_wait;
}
static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio)
@@ -774,10 +762,10 @@ static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg)
struct bio *bio;
if ((bio = bio_list_peek(&tg->bio_lists[READ])))
- tg_may_dispatch(td, tg, bio, &read_wait);
+ read_wait = tg_wait_dispatch(td, tg, bio);
if ((bio = bio_list_peek(&tg->bio_lists[WRITE])))
- tg_may_dispatch(td, tg, bio, &write_wait);
+ write_wait = tg_wait_dispatch(td, tg, bio);
min_wait = min(read_wait, write_wait);
disptime = jiffies + min_wait;
@@ -819,7 +807,7 @@ static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
/* Try to dispatch 75% READS and 25% WRITES */
while ((bio = bio_list_peek(&tg->bio_lists[READ]))
- && tg_may_dispatch(td, tg, bio, NULL)) {
+ && !tg_wait_dispatch(td, tg, bio)) {
tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
nr_reads++;
@@ -829,7 +817,7 @@ static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg,
}
while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))
- && tg_may_dispatch(td, tg, bio, NULL)) {
+ && !tg_wait_dispatch(td, tg, bio)) {
tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl);
nr_writes++;
@@ -1185,7 +1173,7 @@ int blk_throtl_bio(struct request_queue *q, struct bio **biop)
}
/* Bio is with-in rate limit of group */
- if (tg_may_dispatch(td, tg, bio, NULL)) {
+ if (!tg_wait_dispatch(td, tg, bio)) {
throtl_charge_bio(tg, bio);
/*
--
1.7.4.4
--
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