bcache: writeback rate shouldn't artifically clamp
The previous code artificially limited writeback rate to 1000000
blocks/second (NSEC_PER_MSEC), which is a rate that can be met on fast
hardware. The rate limiting code works fine (though with decreased
precision) up to 3 orders of magnitude faster, so use NSEC_PER_SEC.
Additionally, ensure that uint32_t is used as a type for rate throughout
the rate management so that type checking/clamp_t can work properly.
bch_next_delay should be rewritten for increased precision and better
handling of high rates and long sleep periods, but this is adequate for
now.
Signed-off-by: Michael Lyle <[email protected]>
Reported-by: Coly Li <[email protected]>
Reviewed-by: Coly Li <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index eb83be6..d77c4829 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -361,7 +361,7 @@ struct cached_dev {
int64_t writeback_rate_proportional;
int64_t writeback_rate_integral;
int64_t writeback_rate_integral_scaled;
- int64_t writeback_rate_change;
+ int32_t writeback_rate_change;
unsigned writeback_rate_update_seconds;
unsigned writeback_rate_i_term_inverse;
diff --git a/drivers/md/bcache/util.h b/drivers/md/bcache/util.h
index cb8d2cc..8f50929 100644
--- a/drivers/md/bcache/util.h
+++ b/drivers/md/bcache/util.h
@@ -441,10 +441,10 @@ struct bch_ratelimit {
uint64_t next;
/*
- * Rate at which we want to do work, in units per nanosecond
+ * Rate at which we want to do work, in units per second
* The units here correspond to the units passed to bch_next_delay()
*/
- unsigned rate;
+ uint32_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 8deb721..897d280 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -52,7 +52,8 @@ static void __update_writeback_rate(struct cached_dev *dc)
int64_t error = dirty - target;
int64_t proportional_scaled =
div_s64(error, dc->writeback_rate_p_term_inverse);
- int64_t integral_scaled, new_rate;
+ int64_t integral_scaled;
+ uint32_t new_rate;
if ((error < 0 && dc->writeback_rate_integral > 0) ||
(error > 0 && time_before64(local_clock(),
@@ -74,8 +75,8 @@ static void __update_writeback_rate(struct cached_dev *dc)
integral_scaled = div_s64(dc->writeback_rate_integral,
dc->writeback_rate_i_term_inverse);
- new_rate = clamp_t(int64_t, (proportional_scaled + integral_scaled),
- dc->writeback_rate_minimum, NSEC_PER_MSEC);
+ new_rate = clamp_t(int32_t, (proportional_scaled + integral_scaled),
+ dc->writeback_rate_minimum, NSEC_PER_SEC);
dc->writeback_rate_proportional = proportional_scaled;
dc->writeback_rate_integral_scaled = integral_scaled;
