[dm-devel] [PATCH 3/7] dm: add reserved_bio_based_ios module parameter
Mike Snitzer
snitzer at redhat.com
Thu Sep 12 22:24:54 UTC 2013
Allow user to change the number of IOs that are reserved by
bio-based DM's mempools by writing to this file:
/sys/module/dm_mod/parameters/reserved_bio_based_ios
The default value is RESERVED_BIO_BASED_IOS (16).
Signed-off-by: Mike Snitzer <snitzer at redhat.com>
---
drivers/md/dm.c | 42 ++++++++++++++++++++++++++++++++++++++++--
1 file changed, 40 insertions(+), 2 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 8553d03..b44ae19 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -217,6 +217,17 @@ static struct kmem_cache *_io_cache;
static struct kmem_cache *_rq_tio_cache;
/*
+ * Bio-based DM's mempools' reserved IOs set by the user
+ */
+static unsigned reserved_bio_based_ios;
+
+/*
+ * A copy of reserved_bio_based_ios because it can change anytime.
+ * If values disagree, the user has changed reserved_bio_based_ios.
+ */
+static unsigned reserved_bio_based_ios_latch;
+
+/*
* Request-based DM's mempools' reserved IOs set by the user
*/
static unsigned reserved_rq_based_ios;
@@ -228,10 +239,26 @@ static unsigned reserved_rq_based_ios;
static unsigned reserved_rq_based_ios_latch;
/*
- * This mutex protects reserved_rq_based_ios_latch.
+ * This mutex protects reserved_bio_based_ios_latch and reserved_rq_based_ios_latch.
*/
static DEFINE_MUTEX(dm_mempools_lock);
+static void __reserved_bio_based_ios_refresh(void)
+{
+ BUG_ON(!mutex_is_locked(&dm_mempools_lock));
+
+ reserved_bio_based_ios_latch = ACCESS_ONCE(reserved_bio_based_ios);
+
+ /*
+ * If the user uses "0", it means default. Modify
+ * reserved_bio_based_ios to report the default to the user.
+ */
+ if (!reserved_bio_based_ios_latch) {
+ (void)cmpxchg(&reserved_bio_based_ios, 0, RESERVED_BIO_BASED_IOS);
+ reserved_bio_based_ios_latch = reserved_bio_based_ios;
+ }
+}
+
static void __reserved_request_based_ios_refresh(void)
{
BUG_ON(!mutex_is_locked(&dm_mempools_lock));
@@ -274,6 +301,7 @@ static int __init local_init(void)
_major = r;
mutex_lock(&dm_mempools_lock);
+ __reserved_bio_based_ios_refresh();
__reserved_request_based_ios_refresh();
mutex_unlock(&dm_mempools_lock);
@@ -2899,7 +2927,14 @@ struct dm_md_mempools *dm_alloc_md_mempools(unsigned type, unsigned integrity, u
if (type == DM_TYPE_BIO_BASED) {
cachep = _io_cache;
- pool_size = RESERVED_BIO_BASED_IOS;
+
+ mutex_lock(&dm_mempools_lock);
+ /* Check if reserved_bio_based_ios changed. */
+ if (reserved_bio_based_ios != reserved_bio_based_ios_latch)
+ __reserved_bio_based_ios_refresh();
+ pool_size = reserved_bio_based_ios_latch;
+ mutex_unlock(&dm_mempools_lock);
+
front_pad = roundup(per_bio_data_size, __alignof__(struct dm_target_io)) + offsetof(struct dm_target_io, clone);
} else if (type == DM_TYPE_REQUEST_BASED) {
cachep = _rq_tio_cache;
@@ -2969,6 +3004,9 @@ module_exit(dm_exit);
module_param(major, uint, 0);
MODULE_PARM_DESC(major, "The major number of the device mapper");
+module_param(reserved_bio_based_ios, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(reserved_bio_based_ios, "Reserved IOs in bio-based mempools");
+
module_param(reserved_rq_based_ios, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(reserved_rq_based_ios, "Reserved IOs in request-based mempools");
--
1.8.1.4
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