If /sys/modules/dm_mod/parameters/track_peak_rq_based_ios is set to 1 it
enables the tracking of the maximum number of bios in a cloned request.
The maximum number of bios in a cloned request is then exposed through
the following read-only parameter:
/sys/modules/dm_mod/parameters/peak_rq_based_ios
This information can be useful when deciding on a value for dm_mod's
'reserved_rq_based_ios' parameter. Otherwise, 'track_peak_rq_based_ios'
should be kept disabled (the default).
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
drivers/md/dm.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 186f77d..de83930 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -239,6 +239,12 @@ static unsigned reserved_rq_based_ios;
static unsigned reserved_rq_based_ios_latch;
/*
+ * Optionally track the maximum numbers of IOs in a cloned request.
+ */
+static unsigned track_peak_rq_based_ios;
+static unsigned peak_rq_based_ios;
+
+/*
* This mutex protects reserved_bio_based_ios_latch and reserved_rq_based_ios_latch.
*/
static DEFINE_MUTEX(dm_mempools_lock);
@@ -1719,6 +1725,16 @@ static struct request *clone_rq(struct request *rq, struct mapped_device *md,
return NULL;
}
+ if (unlikely(ACCESS_ONCE(track_peak_rq_based_ios))) {
+ struct bio *bio;
+ unsigned num_bios = 0;
+
+ __rq_for_each_bio(bio, clone)
+ num_bios++;
+ if (num_bios > ACCESS_ONCE(peak_rq_based_ios))
+ ACCESS_ONCE(peak_rq_based_ios) = num_bios;
+ }
+
return clone;
}
@@ -3034,6 +3050,12 @@ 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");
+module_param(track_peak_rq_based_ios, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(peak_rq_based_ios, "Enable tracking the maximum IOs in a cloned request");
+
+module_param(peak_rq_based_ios, uint, S_IRUGO);
+MODULE_PARM_DESC(peak_rq_based_ios, "Tracks the maximum IOs in a cloned request");
+
MODULE_DESCRIPTION(DM_NAME " driver");
MODULE_AUTHOR("Joe Thornber <dm-devel@xxxxxxxxxx>");
MODULE_LICENSE("GPL");
--
1.8.1.4
--
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