[PATCH 1/2] dm-kcopyd: introduce per-module throttle structure

[Mikulas Patocka <mpatocka@redhat.com>]

Hi

Here I'm sending new kcopyd throttling patches that allow the throttle to 
be set per module (i.e. one throttle for mirror and the other for 
snapshots).

Mikulas

---

dm-kcopyd: introduce per-module throttle structure

The structure contains the throttle parameter (it could be set in
/sys/module/*/parameters and auxulary variables for activity counting.

The throttle does nothing, it will be activated in the next patch.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
 drivers/md/dm-kcopyd.c    |    2 +-
 drivers/md/dm-raid1.c     |    5 ++++-
 drivers/md/dm-snap.c      |    5 ++++-
 include/linux/dm-kcopyd.h |   15 ++++++++++++++-
 4 files changed, 23 insertions(+), 4 deletions(-)

Index: linux-2.6.39-fast/drivers/md/dm-kcopyd.c
===================================================================
--- linux-2.6.39-fast.orig/drivers/md/dm-kcopyd.c	2011-05-31 23:46:18.000000000 +0200
+++ linux-2.6.39-fast/drivers/md/dm-kcopyd.c	2011-05-31 23:49:47.000000000 +0200
@@ -617,7 +617,7 @@ int kcopyd_cancel(struct kcopyd_job *job
 /*-----------------------------------------------------------------
  * Client setup
  *---------------------------------------------------------------*/
-struct dm_kcopyd_client *dm_kcopyd_client_create(void)
+struct dm_kcopyd_client *dm_kcopyd_client_create(struct dm_kcopyd_throttle *throttle)
 {
 	int r = -ENOMEM;
 	struct dm_kcopyd_client *kc;
Index: linux-2.6.39-fast/drivers/md/dm-raid1.c
===================================================================
--- linux-2.6.39-fast.orig/drivers/md/dm-raid1.c	2011-05-31 23:46:18.000000000 +0200
+++ linux-2.6.39-fast/drivers/md/dm-raid1.c	2011-05-31 23:46:22.000000000 +0200
@@ -83,6 +83,9 @@ struct mirror_set {
 	struct mirror mirror[0];
 };
 
+dm_kcopyd_throttle_declare(raid1_resync_throttle,
+		"A percentage of time allocated for raid resynchronization");
+
 static void wakeup_mirrord(void *context)
 {
 	struct mirror_set *ms = context;
@@ -1115,7 +1118,7 @@ static int mirror_ctr(struct dm_target *
 		goto err_destroy_wq;
 	}
 
-	ms->kcopyd_client = dm_kcopyd_client_create();
+	ms->kcopyd_client = dm_kcopyd_client_create(&dm_kcopyd_throttle);
 	if (IS_ERR(ms->kcopyd_client)) {
 		r = PTR_ERR(ms->kcopyd_client);
 		goto err_destroy_wq;
Index: linux-2.6.39-fast/drivers/md/dm-snap.c
===================================================================
--- linux-2.6.39-fast.orig/drivers/md/dm-snap.c	2011-05-31 23:46:18.000000000 +0200
+++ linux-2.6.39-fast/drivers/md/dm-snap.c	2011-05-31 23:46:22.000000000 +0200
@@ -135,6 +135,9 @@ struct dm_snapshot {
 #define RUNNING_MERGE          0
 #define SHUTDOWN_MERGE         1
 
+dm_kcopyd_throttle_declare(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;
@@ -1111,7 +1114,7 @@ static int snapshot_ctr(struct dm_target
 		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";
Index: linux-2.6.39-fast/include/linux/dm-kcopyd.h
===================================================================
--- linux-2.6.39-fast.orig/include/linux/dm-kcopyd.h	2011-05-31 23:46:18.000000000 +0200
+++ linux-2.6.39-fast/include/linux/dm-kcopyd.h	2011-05-31 23:46:22.000000000 +0200
@@ -21,11 +21,24 @@
 
 #define DM_KCOPYD_IGNORE_ERROR 1
 
+struct dm_kcopyd_throttle {
+	unsigned throttle;
+	unsigned long num_io_jobs;
+	unsigned io_period;
+	unsigned total_period;
+	unsigned last_jiffies;
+};
+
+#define dm_kcopyd_throttle_declare(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.
  */
 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);
 
 /*