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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 /include/linux/dm-kcopyd.h
parenta26062416ef8add48f16fbadded2b5f6fb84d024 (diff)
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 'include/linux/dm-kcopyd.h')
-rw-r--r--include/linux/dm-kcopyd.h25
1 files changed, 24 insertions, 1 deletions
diff --git a/include/linux/dm-kcopyd.h b/include/linux/dm-kcopyd.h
index 47d9d376e4e..f486d636b82 100644
--- a/include/linux/dm-kcopyd.h
+++ b/include/linux/dm-kcopyd.h
@@ -21,11 +21,34 @@
#define DM_KCOPYD_IGNORE_ERROR 1
+struct dm_kcopyd_throttle {
+ unsigned throttle;
+ unsigned num_io_jobs;
+ unsigned io_period;
+ unsigned total_period;
+ unsigned last_jiffies;
+};
+
+/*
+ * kcopyd clients that want to support throttling must pass an initialised
+ * dm_kcopyd_throttle struct into dm_kcopyd_client_create().
+ * Two or more clients may share the same instance of this struct between
+ * them if they wish to be throttled as a group.
+ *
+ * This macro also creates a corresponding module parameter to configure
+ * the amount of throttling.
+ */
+#define DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(name, description) \
+static struct dm_kcopyd_throttle dm_kcopyd_throttle = { 100, 0, 0, 0, 0 }; \
+module_param_named(name, dm_kcopyd_throttle.throttle, uint, 0644); \
+MODULE_PARM_DESC(name, description)
+
/*
* To use kcopyd you must first create a dm_kcopyd_client object.
+ * throttle can be NULL if you don't want any throttling.
*/
struct dm_kcopyd_client;
-struct dm_kcopyd_client *dm_kcopyd_client_create(void);
+struct dm_kcopyd_client *dm_kcopyd_client_create(struct dm_kcopyd_throttle *throttle);
void dm_kcopyd_client_destroy(struct dm_kcopyd_client *kc);
/*