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-rw-r--r--drivers/md/bcache/bcache.h10
-rw-r--r--drivers/md/bcache/request.c59
-rw-r--r--drivers/md/bcache/super.c4
-rw-r--r--drivers/md/bcache/sysfs.c15
-rw-r--r--drivers/md/bcache/util.c2
-rw-r--r--drivers/md/bcache/util.h2
-rw-r--r--drivers/md/bcache/writeback.c91
7 files changed, 138 insertions, 45 deletions
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index b393b3fd06b6..05f82ff6f016 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -328,13 +328,6 @@ struct cached_dev {
*/
atomic_t has_dirty;
- /*
- * Set to zero by things that touch the backing volume-- except
- * writeback. Incremented by writeback. Used to determine when to
- * accelerate idle writeback.
- */
- atomic_t backing_idle;
-
struct bch_ratelimit writeback_rate;
struct delayed_work writeback_rate_update;
@@ -515,6 +508,8 @@ struct cache_set {
struct cache_accounting accounting;
unsigned long flags;
+ atomic_t idle_counter;
+ atomic_t at_max_writeback_rate;
struct cache_sb sb;
@@ -524,6 +519,7 @@ struct cache_set {
struct bcache_device **devices;
unsigned devices_max_used;
+ atomic_t attached_dev_nr;
struct list_head cached_devs;
uint64_t cached_dev_sectors;
atomic_long_t flash_dev_dirty_sectors;
diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c
index 914d501ad1e0..7dbe8b6316a0 100644
--- a/drivers/md/bcache/request.c
+++ b/drivers/md/bcache/request.c
@@ -1103,6 +1103,44 @@ static void detached_dev_do_request(struct bcache_device *d, struct bio *bio)
generic_make_request(bio);
}
+static void quit_max_writeback_rate(struct cache_set *c,
+ struct cached_dev *this_dc)
+{
+ int i;
+ struct bcache_device *d;
+ struct cached_dev *dc;
+
+ /*
+ * mutex bch_register_lock may compete with other parallel requesters,
+ * or attach/detach operations on other backing device. Waiting to
+ * the mutex lock may increase I/O request latency for seconds or more.
+ * To avoid such situation, if mutext_trylock() failed, only writeback
+ * rate of current cached device is set to 1, and __update_write_back()
+ * will decide writeback rate of other cached devices (remember now
+ * c->idle_counter is 0 already).
+ */
+ if (mutex_trylock(&bch_register_lock)) {
+ for (i = 0; i < c->devices_max_used; i++) {
+ if (!c->devices[i])
+ continue;
+
+ if (UUID_FLASH_ONLY(&c->uuids[i]))
+ continue;
+
+ d = c->devices[i];
+ dc = container_of(d, struct cached_dev, disk);
+ /*
+ * set writeback rate to default minimum value,
+ * then let update_writeback_rate() to decide the
+ * upcoming rate.
+ */
+ atomic_long_set(&dc->writeback_rate.rate, 1);
+ }
+ mutex_unlock(&bch_register_lock);
+ } else
+ atomic_long_set(&this_dc->writeback_rate.rate, 1);
+}
+
/* Cached devices - read & write stuff */
static blk_qc_t cached_dev_make_request(struct request_queue *q,
@@ -1120,8 +1158,25 @@ static blk_qc_t cached_dev_make_request(struct request_queue *q,
return BLK_QC_T_NONE;
}
- atomic_set(&dc->backing_idle, 0);
- generic_start_io_acct(q, bio_op(bio), bio_sectors(bio), &d->disk->part0);
+ if (likely(d->c)) {
+ if (atomic_read(&d->c->idle_counter))
+ atomic_set(&d->c->idle_counter, 0);
+ /*
+ * If at_max_writeback_rate of cache set is true and new I/O
+ * comes, quit max writeback rate of all cached devices
+ * attached to this cache set, and set at_max_writeback_rate
+ * to false.
+ */
+ if (unlikely(atomic_read(&d->c->at_max_writeback_rate) == 1)) {
+ atomic_set(&d->c->at_max_writeback_rate, 0);
+ quit_max_writeback_rate(d->c, dc);
+ }
+ }
+
+ generic_start_io_acct(q,
+ bio_op(bio),
+ bio_sectors(bio),
+ &d->disk->part0);
bio_set_dev(bio, dc->bdev);
bio->bi_iter.bi_sector += dc->sb.data_offset;
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 1e85cbb4c159..55a37641aa95 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -696,6 +696,8 @@ static void bcache_device_detach(struct bcache_device *d)
{
lockdep_assert_held(&bch_register_lock);
+ atomic_dec(&d->c->attached_dev_nr);
+
if (test_bit(BCACHE_DEV_DETACHING, &d->flags)) {
struct uuid_entry *u = d->c->uuids + d->id;
@@ -1144,6 +1146,7 @@ int bch_cached_dev_attach(struct cached_dev *dc, struct cache_set *c,
bch_cached_dev_run(dc);
bcache_device_link(&dc->disk, c, "bdev");
+ atomic_inc(&c->attached_dev_nr);
/* Allow the writeback thread to proceed */
up_write(&dc->writeback_lock);
@@ -1696,6 +1699,7 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)
c->block_bits = ilog2(sb->block_size);
c->nr_uuids = bucket_bytes(c) / sizeof(struct uuid_entry);
c->devices_max_used = 0;
+ atomic_set(&c->attached_dev_nr, 0);
c->btree_pages = bucket_pages(c);
if (c->btree_pages > BTREE_MAX_PAGES)
c->btree_pages = max_t(int, c->btree_pages / 4,
diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 3e9d3459a224..6e88142514fb 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -171,7 +171,8 @@ SHOW(__bch_cached_dev)
var_printf(writeback_running, "%i");
var_print(writeback_delay);
var_print(writeback_percent);
- sysfs_hprint(writeback_rate, wb ? dc->writeback_rate.rate << 9 : 0);
+ sysfs_hprint(writeback_rate,
+ wb ? atomic_long_read(&dc->writeback_rate.rate) << 9 : 0);
sysfs_hprint(io_errors, atomic_read(&dc->io_errors));
sysfs_printf(io_error_limit, "%i", dc->error_limit);
sysfs_printf(io_disable, "%i", dc->io_disable);
@@ -193,7 +194,9 @@ SHOW(__bch_cached_dev)
* Except for dirty and target, other values should
* be 0 if writeback is not running.
*/
- bch_hprint(rate, wb ? dc->writeback_rate.rate << 9 : 0);
+ bch_hprint(rate,
+ wb ? atomic_long_read(&dc->writeback_rate.rate) << 9
+ : 0);
bch_hprint(dirty, bcache_dev_sectors_dirty(&dc->disk) << 9);
bch_hprint(target, dc->writeback_rate_target << 9);
bch_hprint(proportional,
@@ -261,8 +264,12 @@ STORE(__cached_dev)
sysfs_strtoul_clamp(writeback_percent, dc->writeback_percent, 0, 40);
- sysfs_strtoul_clamp(writeback_rate,
- dc->writeback_rate.rate, 1, INT_MAX);
+ if (attr == &sysfs_writeback_rate) {
+ int v;
+
+ sysfs_strtoul_clamp(writeback_rate, v, 1, INT_MAX);
+ atomic_long_set(&dc->writeback_rate.rate, v);
+ }
sysfs_strtoul_clamp(writeback_rate_update_seconds,
dc->writeback_rate_update_seconds,
diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
index fc479b026d6d..b15256bcf0e7 100644
--- a/drivers/md/bcache/util.c
+++ b/drivers/md/bcache/util.c
@@ -200,7 +200,7 @@ uint64_t bch_next_delay(struct bch_ratelimit *d, uint64_t done)
{
uint64_t now = local_clock();
- d->next += div_u64(done * NSEC_PER_SEC, d->rate);
+ d->next += div_u64(done * NSEC_PER_SEC, atomic_long_read(&d->rate));
/* Bound the time. Don't let us fall further than 2 seconds behind
* (this prevents unnecessary backlog that would make it impossible
diff --git a/drivers/md/bcache/util.h b/drivers/md/bcache/util.h
index cced87f8eb27..f7b0133c9d2f 100644
--- a/drivers/md/bcache/util.h
+++ b/drivers/md/bcache/util.h
@@ -442,7 +442,7 @@ struct bch_ratelimit {
* Rate at which we want to do work, in units per second
* The units here correspond to the units passed to bch_next_delay()
*/
- uint32_t rate;
+ atomic_long_t rate;
};
static inline void bch_ratelimit_reset(struct bch_ratelimit *d)
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 912e969fedba..481d4cf38ac0 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -104,11 +104,56 @@ static void __update_writeback_rate(struct cached_dev *dc)
dc->writeback_rate_proportional = proportional_scaled;
dc->writeback_rate_integral_scaled = integral_scaled;
- dc->writeback_rate_change = new_rate - dc->writeback_rate.rate;
- dc->writeback_rate.rate = new_rate;
+ dc->writeback_rate_change = new_rate -
+ atomic_long_read(&dc->writeback_rate.rate);
+ atomic_long_set(&dc->writeback_rate.rate, new_rate);
dc->writeback_rate_target = target;
}
+static bool set_at_max_writeback_rate(struct cache_set *c,
+ struct cached_dev *dc)
+{
+ /*
+ * Idle_counter is increased everytime when update_writeback_rate() is
+ * called. If all backing devices attached to the same cache set have
+ * identical dc->writeback_rate_update_seconds values, it is about 6
+ * rounds of update_writeback_rate() on each backing device before
+ * c->at_max_writeback_rate is set to 1, and then max wrteback rate set
+ * to each dc->writeback_rate.rate.
+ * In order to avoid extra locking cost for counting exact dirty cached
+ * devices number, c->attached_dev_nr is used to calculate the idle
+ * throushold. It might be bigger if not all cached device are in write-
+ * back mode, but it still works well with limited extra rounds of
+ * update_writeback_rate().
+ */
+ if (atomic_inc_return(&c->idle_counter) <
+ atomic_read(&c->attached_dev_nr) * 6)
+ return false;
+
+ if (atomic_read(&c->at_max_writeback_rate) != 1)
+ atomic_set(&c->at_max_writeback_rate, 1);
+
+ atomic_long_set(&dc->writeback_rate.rate, INT_MAX);
+
+ /* keep writeback_rate_target as existing value */
+ dc->writeback_rate_proportional = 0;
+ dc->writeback_rate_integral_scaled = 0;
+ dc->writeback_rate_change = 0;
+
+ /*
+ * Check c->idle_counter and c->at_max_writeback_rate agagain in case
+ * new I/O arrives during before set_at_max_writeback_rate() returns.
+ * Then the writeback rate is set to 1, and its new value should be
+ * decided via __update_writeback_rate().
+ */
+ if ((atomic_read(&c->idle_counter) <
+ atomic_read(&c->attached_dev_nr) * 6) ||
+ !atomic_read(&c->at_max_writeback_rate))
+ return false;
+
+ return true;
+}
+
static void update_writeback_rate(struct work_struct *work)
{
struct cached_dev *dc = container_of(to_delayed_work(work),
@@ -136,13 +181,20 @@ static void update_writeback_rate(struct work_struct *work)
return;
}
- down_read(&dc->writeback_lock);
-
- if (atomic_read(&dc->has_dirty) &&
- dc->writeback_percent)
- __update_writeback_rate(dc);
+ if (atomic_read(&dc->has_dirty) && dc->writeback_percent) {
+ /*
+ * If the whole cache set is idle, set_at_max_writeback_rate()
+ * will set writeback rate to a max number. Then it is
+ * unncessary to update writeback rate for an idle cache set
+ * in maximum writeback rate number(s).
+ */
+ if (!set_at_max_writeback_rate(c, dc)) {
+ down_read(&dc->writeback_lock);
+ __update_writeback_rate(dc);
+ up_read(&dc->writeback_lock);
+ }
+ }
- up_read(&dc->writeback_lock);
/*
* CACHE_SET_IO_DISABLE might be set via sysfs interface,
@@ -422,27 +474,6 @@ static void read_dirty(struct cached_dev *dc)
delay = writeback_delay(dc, size);
- /* If the control system would wait for at least half a
- * second, and there's been no reqs hitting the backing disk
- * for awhile: use an alternate mode where we have at most
- * one contiguous set of writebacks in flight at a time. If
- * someone wants to do IO it will be quick, as it will only
- * have to contend with one operation in flight, and we'll
- * be round-tripping data to the backing disk as quickly as
- * it can accept it.
- */
- if (delay >= HZ / 2) {
- /* 3 means at least 1.5 seconds, up to 7.5 if we
- * have slowed way down.
- */
- if (atomic_inc_return(&dc->backing_idle) >= 3) {
- /* Wait for current I/Os to finish */
- closure_sync(&cl);
- /* And immediately launch a new set. */
- delay = 0;
- }
- }
-
while (!kthread_should_stop() &&
!test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
delay) {
@@ -741,7 +772,7 @@ void bch_cached_dev_writeback_init(struct cached_dev *dc)
dc->writeback_running = true;
dc->writeback_percent = 10;
dc->writeback_delay = 30;
- dc->writeback_rate.rate = 1024;
+ atomic_long_set(&dc->writeback_rate.rate, 1024);
dc->writeback_rate_minimum = 8;
dc->writeback_rate_update_seconds = WRITEBACK_RATE_UPDATE_SECS_DEFAULT;
generated by cgit v1.2.3 (git 2.39.0) at 2024-11-24 06:21:20 +0300