mainline inclusion from mainline-5.0-rc1 commit 9aaf51654672b16566c5fe787da3ca41ebf6d297 category: backport
Currently the cutoff writeback and cutoff writeback sync thresholds are defined by CUTOFF_WRITEBACK (40) and CUTOFF_WRITEBACK_SYNC (70) as static values. Most of time these they work fine, but when people want to do research on bcache writeback mode performance tuning, there is no chance to modify the soft and hard cutoff writeback values.
This patch introduces two module parameters bch_cutoff_writeback_sync and bch_cutoff_writeback which permit people to tune the values when loading bcache.ko. If they are not specified by module loading, current values CUTOFF_WRITEBACK_SYNC and CUTOFF_WRITEBACK will be used as default and nothing changes.
When people want to tune this two values, - cutoff_writeback can be set in range [1, 70] - cutoff_writeback_sync can be set in range [1, 90] - cutoff_writeback always <= cutoff_writeback_sync
The default values are strongly recommended to most of users for most of workloads. Anyway, if people wants to take their own risk to do research on new writeback cutoff tuning for their own workload, now they can make it.
Signed-off-by: Coly Li colyli@suse.de Signed-off-by: Jens Axboe axboe@kernel.dk --- drivers/md/bcache/super.c | 40 ++++++++++++++++++++++++++++++++++++++++ drivers/md/bcache/sysfs.c | 7 +++++++ drivers/md/bcache/writeback.h | 10 ++++++++-- 3 files changed, 55 insertions(+), 2 deletions(-)
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index ac54b61ac283..2ad333245674 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -25,6 +25,9 @@ #include <linux/reboot.h> #include <linux/sysfs.h>
+unsigned int bch_cutoff_writeback; +unsigned int bch_cutoff_writeback_sync; + static const char bcache_magic[] = { 0xc6, 0x85, 0x73, 0xf6, 0x4e, 0x1a, 0x45, 0xca, 0x82, 0x65, 0xf5, 0x7f, 0x48, 0xba, 0x6d, 0x81 @@ -2415,6 +2418,32 @@ static void bcache_exit(void) mutex_destroy(&bch_register_lock); }
+/* Check and fixup module parameters */ +static void check_module_parameters(void) +{ + if (bch_cutoff_writeback_sync == 0) + bch_cutoff_writeback_sync = CUTOFF_WRITEBACK_SYNC; + else if (bch_cutoff_writeback_sync > CUTOFF_WRITEBACK_SYNC_MAX) { + pr_warn("set bch_cutoff_writeback_sync (%u) to max value %u", + bch_cutoff_writeback_sync, CUTOFF_WRITEBACK_SYNC_MAX); + bch_cutoff_writeback_sync = CUTOFF_WRITEBACK_SYNC_MAX; + } + + if (bch_cutoff_writeback == 0) + bch_cutoff_writeback = CUTOFF_WRITEBACK; + else if (bch_cutoff_writeback > CUTOFF_WRITEBACK_MAX) { + pr_warn("set bch_cutoff_writeback (%u) to max value %u", + bch_cutoff_writeback, CUTOFF_WRITEBACK_MAX); + bch_cutoff_writeback = CUTOFF_WRITEBACK_MAX; + } + + if (bch_cutoff_writeback > bch_cutoff_writeback_sync) { + pr_warn("set bch_cutoff_writeback (%u) to %u", + bch_cutoff_writeback, bch_cutoff_writeback_sync); + bch_cutoff_writeback = bch_cutoff_writeback_sync; + } +} + static int __init bcache_init(void) { static const struct attribute *files[] = { @@ -2423,6 +2452,8 @@ static int __init bcache_init(void) NULL };
+ check_module_parameters(); + mutex_init(&bch_register_lock); init_waitqueue_head(&unregister_wait); register_reboot_notifier(&reboot); @@ -2459,9 +2490,18 @@ static int __init bcache_init(void) return -ENOMEM; }
+/* + * Module hooks + */ module_exit(bcache_exit); module_init(bcache_init);
+module_param(bch_cutoff_writeback, uint, 0); +MODULE_PARM_DESC(bch_cutoff_writeback, "threshold to cutoff writeback"); + +module_param(bch_cutoff_writeback_sync, uint, 0); +MODULE_PARM_DESC(bch_cutoff_writeback_sync, "hard threshold to cutoff writeback"); + MODULE_DESCRIPTION("Bcache: a Linux block layer cache"); MODULE_AUTHOR("Kent Overstreet kent.overstreet@gmail.com"); MODULE_LICENSE("GPL"); diff --git a/drivers/md/bcache/sysfs.c b/drivers/md/bcache/sysfs.c index 1e8fffa107fb..7cecb17e3798 100644 --- a/drivers/md/bcache/sysfs.c +++ b/drivers/md/bcache/sysfs.c @@ -88,6 +88,8 @@ read_attribute(writeback_keys_done); read_attribute(writeback_keys_failed); read_attribute(io_errors); read_attribute(congested); +read_attribute(cutoff_writeback); +read_attribute(cutoff_writeback_sync); rw_attribute(congested_read_threshold_us); rw_attribute(congested_write_threshold_us);
@@ -699,6 +701,9 @@ SHOW(__bch_cache_set) sysfs_print(congested_write_threshold_us, c->congested_write_threshold_us);
+ sysfs_print(cutoff_writeback, bch_cutoff_writeback); + sysfs_print(cutoff_writeback_sync, bch_cutoff_writeback_sync); + sysfs_print(active_journal_entries, fifo_used(&c->journal.pin)); sysfs_printf(verify, "%i", c->verify); sysfs_printf(key_merging_disabled, "%i", c->key_merging_disabled); @@ -905,6 +910,8 @@ static struct attribute *bch_cache_set_internal_files[] = { &sysfs_copy_gc_enabled, &sysfs_gc_after_writeback, &sysfs_io_disable, + &sysfs_cutoff_writeback, + &sysfs_cutoff_writeback_sync, NULL }; KTYPE(bch_cache_set_internal); diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h index f3bd888a4c7d..4e4c6810dc3c 100644 --- a/drivers/md/bcache/writeback.h +++ b/drivers/md/bcache/writeback.h @@ -5,6 +5,9 @@ #define CUTOFF_WRITEBACK 40 #define CUTOFF_WRITEBACK_SYNC 70
+#define CUTOFF_WRITEBACK_MAX 70 +#define CUTOFF_WRITEBACK_SYNC_MAX 90 + #define MAX_WRITEBACKS_IN_PASS 5 #define MAX_WRITESIZE_IN_PASS 5000 /* *512b */
@@ -55,6 +58,9 @@ static inline bool bcache_dev_stripe_dirty(struct cached_dev *dc, } }
+extern unsigned int bch_cutoff_writeback; +extern unsigned int bch_cutoff_writeback_sync; + static inline bool should_writeback(struct cached_dev *dc, struct bio *bio, unsigned int cache_mode, bool would_skip) { @@ -62,7 +68,7 @@ static inline bool should_writeback(struct cached_dev *dc, struct bio *bio,
if (cache_mode != CACHE_MODE_WRITEBACK || test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) || - in_use > CUTOFF_WRITEBACK_SYNC) + in_use > bch_cutoff_writeback_sync) return false;
if (bio_op(bio) == REQ_OP_DISCARD) @@ -78,7 +84,7 @@ static inline bool should_writeback(struct cached_dev *dc, struct bio *bio,
return (op_is_sync(bio->bi_opf) || bio->bi_opf & (REQ_META|REQ_PRIO) || - in_use <= CUTOFF_WRITEBACK); + in_use <= bch_cutoff_writeback); }
static inline void bch_writeback_queue(struct cached_dev *dc)