From: Tang Junhui <tang.junhui@xxxxxxxxxx>
When there is not enough dirty data in writeback cache,
writeback rate is at minimum 1 key per second
util all dirty data to be cleaned, it is inefficiency,
and also causes waste of energy;
in this patch, When there is not enough dirty data,
let the writeback rate to be 0, and writeback re-schedule
in bch_writeback_thread() periodically with schedule_timeout(),
the behaviors are as follows :
1) If no dirty data have been read into dc->writeback_keys,
goto step 2), otherwise keep writing these dirty data to
back-end device at 1 key per second, until all these dirty data
write over, then goto step 2).
2) Loop in bch_writeback_thread() to check if there is enough
dirty data for writeback. if there is not enough diry data for
writing, then sleep 10 seconds, otherwise, write dirty data to
back-end device.
Signed-off-by: Tang Junhui <tang.junhui@xxxxxxxxxx>
---
drivers/md/bcache/util.c | 9 ++++++++-
drivers/md/bcache/writeback.c | 11 +++++++----
2 files changed, 15 insertions(+), 5 deletions(-)
diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c
index 8c3a938..49dcf09 100644
--- a/drivers/md/bcache/util.c
+++ b/drivers/md/bcache/util.c
@@ -210,7 +210,14 @@ 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);
+ /*
+ if d->rate is zero, write the left dirty data
+ at the speed of one key per second
+ */
+ if(!d->rate)
+ d->next = now + NSEC_PER_SEC;
+ else
+ d->next += div_u64(done * NSEC_PER_SEC, d->rate);
if (time_before64(now + NSEC_PER_SEC, d->next))
d->next = now + NSEC_PER_SEC;
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 25289e4..4104eaa 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -16,6 +16,8 @@
#include <linux/sched/clock.h>
#include <trace/events/bcache.h>
+#define WRITE_BACK_WAIT_CYCLE 10 * HZ
+
/* Rate limiting */
static void __update_writeback_rate(struct cached_dev *dc)
@@ -55,13 +57,14 @@ static void __update_writeback_rate(struct cached_dev *dc)
/* Don't increase writeback rate if the device isn't keeping up */
if (change > 0 &&
+ dc->writeback_rate.rate >0 &&
time_after64(local_clock(),
dc->writeback_rate.next + NSEC_PER_MSEC))
change = 0;
dc->writeback_rate.rate =
clamp_t(int64_t, (int64_t) dc->writeback_rate.rate + change,
- 1, NSEC_PER_MSEC);
+ 0, NSEC_PER_MSEC);
dc->writeback_rate_proportional = proportional;
dc->writeback_rate_derivative = derivative;
@@ -420,15 +423,15 @@ static int bch_writeback_thread(void *arg)
while (!kthread_should_stop()) {
down_write(&dc->writeback_lock);
if (!atomic_read(&dc->has_dirty) ||
- (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&
- !dc->writeback_running)) {
+ ((!dc->writeback_rate.rate || !dc->writeback_running) &&
+ !test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))) {
up_write(&dc->writeback_lock);
set_current_state(TASK_INTERRUPTIBLE);
if (kthread_should_stop())
return 0;
- schedule();
+ schedule_timeout(WRITE_BACK_WAIT_CYCLE);
continue;
}
--
1.8.3.1
