bcache: New writeback PD controller
The old writeback PD controller could get into states where it had throttled all
the way down and take way too long to recover - it was too complicated to really
understand what it was doing.
This rewrites a good chunk of it to hopefully be simpler and make more sense,
and it also pays more attention to units which should make the behaviour a bit
easier to understand.
Signed-off-by: Kent Overstreet <kmo@daterainc.com>
diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 80d4c2b..a1f8561 100644
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -83,7 +83,6 @@
rw_attribute(writeback_rate_update_seconds);
rw_attribute(writeback_rate_d_term);
rw_attribute(writeback_rate_p_term_inverse);
-rw_attribute(writeback_rate_d_smooth);
read_attribute(writeback_rate_debug);
read_attribute(stripe_size);
@@ -129,31 +128,41 @@
var_printf(writeback_running, "%i");
var_print(writeback_delay);
var_print(writeback_percent);
- sysfs_print(writeback_rate, dc->writeback_rate.rate);
+ sysfs_hprint(writeback_rate, dc->writeback_rate.rate << 9);
var_print(writeback_rate_update_seconds);
var_print(writeback_rate_d_term);
var_print(writeback_rate_p_term_inverse);
- var_print(writeback_rate_d_smooth);
if (attr == &sysfs_writeback_rate_debug) {
+ char rate[20];
char dirty[20];
- char derivative[20];
char target[20];
- bch_hprint(dirty,
- bcache_dev_sectors_dirty(&dc->disk) << 9);
- bch_hprint(derivative, dc->writeback_rate_derivative << 9);
+ char proportional[20];
+ char derivative[20];
+ char change[20];
+ s64 next_io;
+
+ bch_hprint(rate, dc->writeback_rate.rate << 9);
+ bch_hprint(dirty, bcache_dev_sectors_dirty(&dc->disk) << 9);
bch_hprint(target, dc->writeback_rate_target << 9);
+ bch_hprint(proportional,dc->writeback_rate_proportional << 9);
+ bch_hprint(derivative, dc->writeback_rate_derivative << 9);
+ bch_hprint(change, dc->writeback_rate_change << 9);
+
+ next_io = div64_s64(dc->writeback_rate.next - local_clock(),
+ NSEC_PER_MSEC);
return sprintf(buf,
- "rate:\t\t%u\n"
- "change:\t\t%i\n"
+ "rate:\t\t%s/sec\n"
"dirty:\t\t%s\n"
+ "target:\t\t%s\n"
+ "proportional:\t%s\n"
"derivative:\t%s\n"
- "target:\t\t%s\n",
- dc->writeback_rate.rate,
- dc->writeback_rate_change,
- dirty, derivative, target);
+ "change:\t\t%s/sec\n"
+ "next io:\t%llims\n",
+ rate, dirty, target, proportional,
+ derivative, change, next_io);
}
sysfs_hprint(dirty_data,
@@ -189,6 +198,7 @@
struct kobj_uevent_env *env;
#define d_strtoul(var) sysfs_strtoul(var, dc->var)
+#define d_strtoul_nonzero(var) sysfs_strtoul_clamp(var, dc->var, 1, INT_MAX)
#define d_strtoi_h(var) sysfs_hatoi(var, dc->var)
sysfs_strtoul(data_csum, dc->disk.data_csum);
@@ -197,16 +207,15 @@
d_strtoul(writeback_metadata);
d_strtoul(writeback_running);
d_strtoul(writeback_delay);
- sysfs_strtoul_clamp(writeback_rate,
- dc->writeback_rate.rate, 1, 1000000);
+
sysfs_strtoul_clamp(writeback_percent, dc->writeback_percent, 0, 40);
- d_strtoul(writeback_rate_update_seconds);
+ sysfs_strtoul_clamp(writeback_rate,
+ dc->writeback_rate.rate, 1, INT_MAX);
+
+ d_strtoul_nonzero(writeback_rate_update_seconds);
d_strtoul(writeback_rate_d_term);
- d_strtoul(writeback_rate_p_term_inverse);
- sysfs_strtoul_clamp(writeback_rate_p_term_inverse,
- dc->writeback_rate_p_term_inverse, 1, INT_MAX);
- d_strtoul(writeback_rate_d_smooth);
+ d_strtoul_nonzero(writeback_rate_p_term_inverse);
d_strtoi_h(sequential_cutoff);
d_strtoi_h(readahead);
@@ -313,7 +322,6 @@
&sysfs_writeback_rate_update_seconds,
&sysfs_writeback_rate_d_term,
&sysfs_writeback_rate_p_term_inverse,
- &sysfs_writeback_rate_d_smooth,
&sysfs_writeback_rate_debug,
&sysfs_dirty_data,
&sysfs_stripe_size,