bcache: add idle_max_writeback_rate sysfs interface

For writeback mode, if there is no regular I/O request for a while,
the writeback rate will be set to the maximum value (1TB/s for now).
This is good for most of the storage workload, but there are still
people don't what the maximum writeback rate in I/O idle time.

This patch adds a sysfs interface file idle_max_writeback_rate to
permit people to disable maximum writeback rate. Then the minimum
writeback rate can be advised by writeback_rate_minimum in the
bcache device's sysfs interface.

Reported-by: Christian Balzer <chibi@gol.com>
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 50241e0..9198c1b 100644 (file)
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -724,6 +724,7 @@ struct cache_set {
        unsigned int            gc_always_rewrite:1;
        unsigned int            shrinker_disabled:1;
        unsigned int            copy_gc_enabled:1;
+       unsigned int            idle_max_writeback_rate_enabled:1;
 
 #define BUCKET_HASH_BITS       12
        struct hlist_head       bucket_hash[1 << BUCKET_HASH_BITS];

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index d1352fc..77e9869 100644 (file)
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1834,6 +1834,7 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)
        c->congested_read_threshold_us  = 2000;
        c->congested_write_threshold_us = 20000;
        c->error_limit  = DEFAULT_IO_ERROR_LIMIT;
+       c->idle_max_writeback_rate_enabled = 1;
        WARN_ON(test_and_clear_bit(CACHE_SET_IO_DISABLE, &c->flags));
 
        return c;

diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c
index 627dcea..733e2dd 100644 (file)
--- a/drivers/md/bcache/sysfs.c
+++ b/drivers/md/bcache/sysfs.c
@@ -134,6 +134,7 @@ rw_attribute(expensive_debug_checks);
 rw_attribute(cache_replacement_policy);
 rw_attribute(btree_shrinker_disabled);
 rw_attribute(copy_gc_enabled);
+rw_attribute(idle_max_writeback_rate);
 rw_attribute(gc_after_writeback);
 rw_attribute(size);
 
@@ -747,6 +748,8 @@ SHOW(__bch_cache_set)
        sysfs_printf(gc_always_rewrite,         "%i", c->gc_always_rewrite);
        sysfs_printf(btree_shrinker_disabled,   "%i", c->shrinker_disabled);
        sysfs_printf(copy_gc_enabled,           "%i", c->copy_gc_enabled);
+       sysfs_printf(idle_max_writeback_rate,   "%i",
+                    c->idle_max_writeback_rate_enabled);
        sysfs_printf(gc_after_writeback,        "%i", c->gc_after_writeback);
        sysfs_printf(io_disable,                "%i",
                     test_bit(CACHE_SET_IO_DISABLE, &c->flags));
@@ -864,6 +867,9 @@ STORE(__bch_cache_set)
        sysfs_strtoul_bool(gc_always_rewrite,   c->gc_always_rewrite);
        sysfs_strtoul_bool(btree_shrinker_disabled, c->shrinker_disabled);
        sysfs_strtoul_bool(copy_gc_enabled,     c->copy_gc_enabled);
+       sysfs_strtoul_bool(idle_max_writeback_rate,
+                          c->idle_max_writeback_rate_enabled);
+
        /*
         * write gc_after_writeback here may overwrite an already set
         * BCH_DO_AUTO_GC, it doesn't matter because this flag will be
@@ -954,6 +960,7 @@ static struct attribute *bch_cache_set_internal_files[] = {
        &sysfs_gc_always_rewrite,
        &sysfs_btree_shrinker_disabled,
        &sysfs_copy_gc_enabled,
+       &sysfs_idle_max_writeback_rate,
        &sysfs_gc_after_writeback,
        &sysfs_io_disable,
        &sysfs_cutoff_writeback,

diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index d60268f..4a40f9e 100644 (file)
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -122,6 +122,10 @@ static void __update_writeback_rate(struct cached_dev *dc)
 static bool set_at_max_writeback_rate(struct cache_set *c,
                                       struct cached_dev *dc)
 {
+       /* Don't sst max writeback rate if it is disabled */
+       if (!c->idle_max_writeback_rate_enabled)
+               return false;
+
        /* Don't set max writeback rate if gc is running */
        if (!c->gc_mark_valid)
                return false;