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authorMikulas Patocka <mpatocka@redhat.com>2013-03-01 22:45:49 +0000
committerAlasdair G Kergon <agk@redhat.com>2013-03-01 22:45:49 +0000
commitdf5d2e9089c7d5b8c46f767e4278610ea3e815b9 (patch)
tree5285aa8b0c794da419133a209437b32a11aa8a8d /drivers/md/dm-snap.c
parenta26062416ef8add48f16fbadded2b5f6fb84d024 (diff)
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dm kcopyd: introduce configurable throttling
This patch allows the administrator to reduce the rate at which kcopyd issues I/O. Each module that uses kcopyd acquires a throttle parameter that can be set in /sys/module/*/parameters. We maintain a history of kcopyd usage by each module in the variables io_period and total_period in struct dm_kcopyd_throttle. The actual kcopyd activity is calculated as a percentage of time equal to "(100 * io_period / total_period)". This is compared with the user-defined throttle percentage threshold and if it is exceeded, we sleep. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md/dm-snap.c')
-rw-r--r--drivers/md/dm-snap.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 58c2b58..c0e0702 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -124,6 +124,9 @@ struct dm_snapshot {
#define RUNNING_MERGE 0
#define SHUTDOWN_MERGE 1
+DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle,
+ "A percentage of time allocated for copy on write");
+
struct dm_dev *dm_snap_origin(struct dm_snapshot *s)
{
return s->origin;
@@ -1108,7 +1111,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
goto bad_hash_tables;
}
- s->kcopyd_client = dm_kcopyd_client_create();
+ s->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
if (IS_ERR(s->kcopyd_client)) {
r = PTR_ERR(s->kcopyd_client);
ti->error = "Could not create kcopyd client";