1 files changed, 339 insertions, 0 deletions
diff --git a/drivers/md/dm-service-time.c b/drivers/md/dm-service-time.c
new file mode 100644
index 000000000000..cfa668f46c40
--- /dev/null
+++ b/drivers/md/dm-service-time.c
@@ -0,0 +1,339 @@
+/*
+ * Copyright (C) 2007-2009 NEC Corporation.  All Rights Reserved.
+ *
+ * Module Author: Kiyoshi Ueda
+ *
+ * This file is released under the GPL.
+ *
+ * Throughput oriented path selector.
+ */
+#include "dm.h"
+#include "dm-path-selector.h"
+#define DM_MSG_PREFIX   "multipath service-time"
+#define ST_MIN_IO       1
+#define ST_MAX_RELATIVE_THROUGHPUT      100
+#define ST_MAX_RELATIVE_THROUGHPUT_SHIFT        7
+#define ST_MAX_INFLIGHT_SIZE    ((size_t)-1 >> ST_MAX_RELATIVE_THROUGHPUT_SHIFT)
+#define ST_VERSION      "0.2.0"
+struct selector {
+        struct list_head valid_paths;
+        struct list_head failed_paths;
+};
+struct path_info {
+        struct list_head list;
+        struct dm_path *path;
+        unsigned repeat_count;
+        unsigned relative_throughput;
+        atomic_t in_flight_size;        /* Total size of in-flight I/Os */
+};
+static struct selector *alloc_selector(void)
+{
+        struct selector *s = kmalloc(sizeof(*s), GFP_KERNEL);
+        if (s) {
+                INIT_LIST_HEAD(&s->valid_paths);
+                INIT_LIST_HEAD(&s->failed_paths);
+        }
+        return s;
+}
+static int st_create(struct path_selector *ps, unsigned argc, char **argv)
+{
+        struct selector *s = alloc_selector();
+        if (!s)
+                return -ENOMEM;
+        ps->context = s;
+        return 0;
+}
+static void free_paths(struct list_head *paths)
+{
+        struct path_info *pi, *next;
+        list_for_each_entry_safe(pi, next, paths, list) {
+                list_del(&pi->list);
+                kfree(pi);
+        }
+}
+static void st_destroy(struct path_selector *ps)
+{
+        struct selector *s = ps->context;
+        free_paths(&s->valid_paths);
+        free_paths(&s->failed_paths);
+        kfree(s);
+        ps->context = NULL;
+}
+static int st_status(struct path_selector *ps, struct dm_path *path,
+                     status_type_t type, char *result, unsigned maxlen)
+{
+        unsigned sz = 0;
+        struct path_info *pi;
+        if (!path)
+                DMEMIT("0 ");
+        else {
+                pi = path->pscontext;
+                switch (type) {
+                case STATUSTYPE_INFO:
+                        DMEMIT("%d %u ", atomic_read(&pi->in_flight_size),
+                               pi->relative_throughput);
+                        break;
+                case STATUSTYPE_TABLE:
+                        DMEMIT("%u %u ", pi->repeat_count,
+                               pi->relative_throughput);
+                        break;
+                }
+        }
+        return sz;
+}
+static int st_add_path(struct path_selector *ps, struct dm_path *path,
+                       int argc, char **argv, char **error)
+{
+        struct selector *s = ps->context;
+        struct path_info *pi;
+        unsigned repeat_count = ST_MIN_IO;
+        unsigned relative_throughput = 1;
+        /*
+         * Arguments: [<repeat_count> [<relative_throughput>]]
+         *      <repeat_count>: The number of I/Os before switching path.
+         *                      If not given, default (ST_MIN_IO) is used.
+         *      <relative_throughput>: The relative throughput value of
+         *                      the path among all paths in the path-group.
+         *                      The valid range: 0-<ST_MAX_RELATIVE_THROUGHPUT>
+         *                      If not given, minimum value '1' is used.
+         *                      If '0' is given, the path isn't selected while
+         *                      other paths having a positive value are
+         *                      available.
+         */
+        if (argc > 2) {
+                *error = "service-time ps: incorrect number of arguments";
+                return -EINVAL;
+        }
+        if (argc && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
+                *error = "service-time ps: invalid repeat count";
+                return -EINVAL;
+        }
+        if ((argc == 2) &&
+            (sscanf(argv[1], "%u", &relative_throughput) != 1 ||
+             relative_throughput > ST_MAX_RELATIVE_THROUGHPUT)) {
+                *error = "service-time ps: invalid relative_throughput value";
+                return -EINVAL;
+        }
+        /* allocate the path */
+        pi = kmalloc(sizeof(*pi), GFP_KERNEL);
+        if (!pi) {
+                *error = "service-time ps: Error allocating path context";
+                return -ENOMEM;
+        }
+        pi->path = path;
+        pi->repeat_count = repeat_count;
+        pi->relative_throughput = relative_throughput;
+        atomic_set(&pi->in_flight_size, 0);
+        path->pscontext = pi;
+        list_add_tail(&pi->list, &s->valid_paths);
+        return 0;
+}
+static void st_fail_path(struct path_selector *ps, struct dm_path *path)
+{
+        struct selector *s = ps->context;
+        struct path_info *pi = path->pscontext;
+        list_move(&pi->list, &s->failed_paths);
+}
+static int st_reinstate_path(struct path_selector *ps, struct dm_path *path)
+{
+        struct selector *s = ps->context;
+        struct path_info *pi = path->pscontext;
+        list_move_tail(&pi->list, &s->valid_paths);
+        return 0;
+}
+/*
+ * Compare the estimated service time of 2 paths, pi1 and pi2,
+ * for the incoming I/O.
+ *
+ * Returns:
+ * < 0 : pi1 is better
+ * 0   : no difference between pi1 and pi2
+ * > 0 : pi2 is better
+ *
+ * Description:
+ * Basically, the service time is estimated by:
+ *     ('pi->in-flight-size' + 'incoming') / 'pi->relative_throughput'
+ * To reduce the calculation, some optimizations are made.
+ * (See comments inline)
+ */
+static int st_compare_load(struct path_info *pi1, struct path_info *pi2,
+                           size_t incoming)
+{
+        size_t sz1, sz2, st1, st2;
+        sz1 = atomic_read(&pi1->in_flight_size);
+        sz2 = atomic_read(&pi2->in_flight_size);
+        /*
+         * Case 1: Both have same throughput value. Choose less loaded path.
+         */
+        if (pi1->relative_throughput == pi2->relative_throughput)
+                return sz1 - sz2;
+        /*
+         * Case 2a: Both have same load. Choose higher throughput path.
+         * Case 2b: One path has no throughput value. Choose the other one.
+         */
+        if (sz1 == sz2 ||
+            !pi1->relative_throughput || !pi2->relative_throughput)
+                return pi2->relative_throughput - pi1->relative_throughput;
+        /*
+         * Case 3: Calculate service time. Choose faster path.
+         *         Service time using pi1:
+         *             st1 = (sz1 + incoming) / pi1->relative_throughput
+         *         Service time using pi2:
+         *             st2 = (sz2 + incoming) / pi2->relative_throughput
+         *
+         *         To avoid the division, transform the expression to use
+         *         multiplication.
+         *         Because ->relative_throughput > 0 here, if st1 < st2,
+         *         the expressions below are the same meaning:
+         *             (sz1 + incoming) / pi1->relative_throughput <
+         *                 (sz2 + incoming) / pi2->relative_throughput
+         *             (sz1 + incoming) * pi2->relative_throughput <
+         *                 (sz2 + incoming) * pi1->relative_throughput
+         *         So use the later one.
+         */
+        sz1 += incoming;
+        sz2 += incoming;
+        if (unlikely(sz1 >= ST_MAX_INFLIGHT_SIZE ||
+                     sz2 >= ST_MAX_INFLIGHT_SIZE)) {
+                /*
+                 * Size may be too big for multiplying pi->relative_throughput
+                 * and overflow.
+                 * To avoid the overflow and mis-selection, shift down both.
+                 */
+                sz1 >>= ST_MAX_RELATIVE_THROUGHPUT_SHIFT;
+                sz2 >>= ST_MAX_RELATIVE_THROUGHPUT_SHIFT;
+        }
+        st1 = sz1 * pi2->relative_throughput;
+        st2 = sz2 * pi1->relative_throughput;
+        if (st1 != st2)
+                return st1 - st2;
+        /*
+         * Case 4: Service time is equal. Choose higher throughput path.
+         */
+        return pi2->relative_throughput - pi1->relative_throughput;
+}
+static struct dm_path *st_select_path(struct path_selector *ps,
+                                      unsigned *repeat_count, size_t nr_bytes)
+{
+        struct selector *s = ps->context;
+        struct path_info *pi = NULL, *best = NULL;
+        if (list_empty(&s->valid_paths))
+                return NULL;
+        /* Change preferred (first in list) path to evenly balance. */
+        list_move_tail(s->valid_paths.next, &s->valid_paths);
+        list_for_each_entry(pi, &s->valid_paths, list)
+                if (!best || (st_compare_load(pi, best, nr_bytes) < 0))
+                        best = pi;
+        if (!best)
+                return NULL;
+        *repeat_count = best->repeat_count;
+        return best->path;
+}
+static int st_start_io(struct path_selector *ps, struct dm_path *path,
+                       size_t nr_bytes)
+{
+        struct path_info *pi = path->pscontext;
+        atomic_add(nr_bytes, &pi->in_flight_size);
+        return 0;
+}
+static int st_end_io(struct path_selector *ps, struct dm_path *path,
+                     size_t nr_bytes)
+{
+        struct path_info *pi = path->pscontext;
+        atomic_sub(nr_bytes, &pi->in_flight_size);
+        return 0;
+}
+static struct path_selector_type st_ps = {
+        .name           = "service-time",
+        .module         = THIS_MODULE,
+        .table_args     = 2,
+        .info_args      = 2,
+        .create         = st_create,
+        .destroy        = st_destroy,
+        .status         = st_status,
+        .add_path       = st_add_path,
+        .fail_path      = st_fail_path,
+        .reinstate_path = st_reinstate_path,
+        .select_path    = st_select_path,
+        .start_io       = st_start_io,
+        .end_io         = st_end_io,
+};
+static int __init dm_st_init(void)
+{
+        int r = dm_register_path_selector(&st_ps);
+        if (r < 0)
+                DMERR("register failed %d", r);
+        DMINFO("version " ST_VERSION " loaded");
+        return r;
+}
+static void __exit dm_st_exit(void)
+{
+        int r = dm_unregister_path_selector(&st_ps);
+        if (r < 0)
+                DMERR("unregister failed %d", r);
+}
+module_init(dm_st_init);
+module_exit(dm_st_exit);
+MODULE_DESCRIPTION(DM_NAME " throughput oriented path selector");
+MODULE_AUTHOR("Kiyoshi Ueda <k-ueda@ct.jp.nec.com>");
+MODULE_LICENSE("GPL");

diff --git a/drivers/md/dm-service-time.c b/drivers/md/dm-service-time.c new file mode 100644 index 000000000000..cfa668f46c40 --- /dev/null +++ b/drivers/md/dm-service-time.c
@@ -0,0 +1,339 @@
	1	/*
	2	* Copyright (C) 2007-2009 NEC Corporation. All Rights Reserved.
	3	*
	4	* Module Author: Kiyoshi Ueda
	5	*
	6	* This file is released under the GPL.
	7	*
	8	* Throughput oriented path selector.
	9	*/
	10
	11	#include "dm.h"
	12	#include "dm-path-selector.h"
	13
	14	#define DM_MSG_PREFIX "multipath service-time"
	15	#define ST_MIN_IO 1
	16	#define ST_MAX_RELATIVE_THROUGHPUT 100
	17	#define ST_MAX_RELATIVE_THROUGHPUT_SHIFT 7
	18	#define ST_MAX_INFLIGHT_SIZE ((size_t)-1 >> ST_MAX_RELATIVE_THROUGHPUT_SHIFT)
	19	#define ST_VERSION "0.2.0"
	20
	21	struct selector {
	22	struct list_head valid_paths;
	23	struct list_head failed_paths;
	24	};
	25
	26	struct path_info {
	27	struct list_head list;
	28	struct dm_path *path;
	29	unsigned repeat_count;
	30	unsigned relative_throughput;
	31	atomic_t in_flight_size; /* Total size of in-flight I/Os */
	32	};
	33
	34	static struct selector *alloc_selector(void)
	35	{
	36	struct selector s = kmalloc(sizeof(s), GFP_KERNEL);
	37
	38	if (s) {
	39	INIT_LIST_HEAD(&s->valid_paths);
	40	INIT_LIST_HEAD(&s->failed_paths);
	41	}
	42
	43	return s;
	44	}
	45
	46	static int st_create(struct path_selector ps, unsigned argc, char *argv)
	47	{
	48	struct selector *s = alloc_selector();
	49
	50	if (!s)
	51	return -ENOMEM;
	52
	53	ps->context = s;
	54	return 0;
	55	}
	56
	57	static void free_paths(struct list_head *paths)
	58	{
	59	struct path_info pi, next;
	60
	61	list_for_each_entry_safe(pi, next, paths, list) {
	62	list_del(&pi->list);
	63	kfree(pi);
	64	}
	65	}
	66
	67	static void st_destroy(struct path_selector *ps)
	68	{
	69	struct selector *s = ps->context;
	70
	71	free_paths(&s->valid_paths);
	72	free_paths(&s->failed_paths);
	73	kfree(s);
	74	ps->context = NULL;
	75	}
	76
	77	static int st_status(struct path_selector ps, struct dm_path path,
	78	status_type_t type, char *result, unsigned maxlen)
	79	{
	80	unsigned sz = 0;
	81	struct path_info *pi;
	82
	83	if (!path)
	84	DMEMIT("0 ");
	85	else {
	86	pi = path->pscontext;
	87
	88	switch (type) {
	89	case STATUSTYPE_INFO:
	90	DMEMIT("%d %u ", atomic_read(&pi->in_flight_size),
	91	pi->relative_throughput);
	92	break;
	93	case STATUSTYPE_TABLE:
	94	DMEMIT("%u %u ", pi->repeat_count,
	95	pi->relative_throughput);
	96	break;
	97	}
	98	}
	99
	100	return sz;
	101	}
	102
	103	static int st_add_path(struct path_selector ps, struct dm_path path,
	104	int argc, char argv, char error)
	105	{
	106	struct selector *s = ps->context;
	107	struct path_info *pi;
	108	unsigned repeat_count = ST_MIN_IO;
	109	unsigned relative_throughput = 1;
	110
	111	/*
	112	* Arguments: [<repeat_count> [<relative_throughput>]]
	113	* <repeat_count>: The number of I/Os before switching path.
	114	* If not given, default (ST_MIN_IO) is used.
	115	* <relative_throughput>: The relative throughput value of
	116	* the path among all paths in the path-group.
	117	* The valid range: 0-<ST_MAX_RELATIVE_THROUGHPUT>
	118	* If not given, minimum value '1' is used.
	119	* If '0' is given, the path isn't selected while
	120	* other paths having a positive value are
	121	* available.
	122	*/
	123	if (argc > 2) {
	124	*error = "service-time ps: incorrect number of arguments";
	125	return -EINVAL;
	126	}
	127
	128	if (argc && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
	129	*error = "service-time ps: invalid repeat count";
	130	return -EINVAL;
	131	}
	132
	133	if ((argc == 2) &&
	134	(sscanf(argv[1], "%u", &relative_throughput) != 1 \|\|
	135	relative_throughput > ST_MAX_RELATIVE_THROUGHPUT)) {
	136	*error = "service-time ps: invalid relative_throughput value";
	137	return -EINVAL;
	138	}
	139
	140	/* allocate the path */
	141	pi = kmalloc(sizeof(*pi), GFP_KERNEL);
	142	if (!pi) {
	143	*error = "service-time ps: Error allocating path context";
	144	return -ENOMEM;
	145	}
	146
	147	pi->path = path;
	148	pi->repeat_count = repeat_count;
	149	pi->relative_throughput = relative_throughput;
	150	atomic_set(&pi->in_flight_size, 0);
	151
	152	path->pscontext = pi;
	153
	154	list_add_tail(&pi->list, &s->valid_paths);
	155
	156	return 0;
	157	}
	158
	159	static void st_fail_path(struct path_selector ps, struct dm_path path)
	160	{
	161	struct selector *s = ps->context;
	162	struct path_info *pi = path->pscontext;
	163
	164	list_move(&pi->list, &s->failed_paths);
	165	}
	166
	167	static int st_reinstate_path(struct path_selector ps, struct dm_path path)
	168	{
	169	struct selector *s = ps->context;
	170	struct path_info *pi = path->pscontext;
	171
	172	list_move_tail(&pi->list, &s->valid_paths);
	173
	174	return 0;
	175	}
	176
	177	/*
	178	* Compare the estimated service time of 2 paths, pi1 and pi2,
	179	* for the incoming I/O.
	180	*
	181	* Returns:
	182	* < 0 : pi1 is better
	183	* 0 : no difference between pi1 and pi2
	184	* > 0 : pi2 is better
	185	*
	186	* Description:
	187	* Basically, the service time is estimated by:
	188	* ('pi->in-flight-size' + 'incoming') / 'pi->relative_throughput'
	189	* To reduce the calculation, some optimizations are made.
	190	* (See comments inline)
	191	*/
	192	static int st_compare_load(struct path_info pi1, struct path_info pi2,
	193	size_t incoming)
	194	{
	195	size_t sz1, sz2, st1, st2;
	196
	197	sz1 = atomic_read(&pi1->in_flight_size);
	198	sz2 = atomic_read(&pi2->in_flight_size);
	199
	200	/*
	201	* Case 1: Both have same throughput value. Choose less loaded path.
	202	*/
	203	if (pi1->relative_throughput == pi2->relative_throughput)
	204	return sz1 - sz2;
	205
	206	/*
	207	* Case 2a: Both have same load. Choose higher throughput path.
	208	* Case 2b: One path has no throughput value. Choose the other one.
	209	*/
	210	if (sz1 == sz2 \|\|
	211	!pi1->relative_throughput \|\| !pi2->relative_throughput)
	212	return pi2->relative_throughput - pi1->relative_throughput;
	213
	214	/*
	215	* Case 3: Calculate service time. Choose faster path.
	216	* Service time using pi1:
	217	* st1 = (sz1 + incoming) / pi1->relative_throughput
	218	* Service time using pi2:
	219	* st2 = (sz2 + incoming) / pi2->relative_throughput
	220	*
	221	* To avoid the division, transform the expression to use
	222	* multiplication.
	223	* Because ->relative_throughput > 0 here, if st1 < st2,
	224	* the expressions below are the same meaning:
	225	* (sz1 + incoming) / pi1->relative_throughput <
	226	* (sz2 + incoming) / pi2->relative_throughput
	227	* (sz1 + incoming) * pi2->relative_throughput <
	228	* (sz2 + incoming) * pi1->relative_throughput
	229	* So use the later one.
	230	*/
	231	sz1 += incoming;
	232	sz2 += incoming;
	233	if (unlikely(sz1 >= ST_MAX_INFLIGHT_SIZE \|\|
	234	sz2 >= ST_MAX_INFLIGHT_SIZE)) {
	235	/*
	236	* Size may be too big for multiplying pi->relative_throughput
	237	* and overflow.
	238	* To avoid the overflow and mis-selection, shift down both.
	239	*/
	240	sz1 >>= ST_MAX_RELATIVE_THROUGHPUT_SHIFT;
	241	sz2 >>= ST_MAX_RELATIVE_THROUGHPUT_SHIFT;
	242	}
	243	st1 = sz1 * pi2->relative_throughput;
	244	st2 = sz2 * pi1->relative_throughput;
	245	if (st1 != st2)
	246	return st1 - st2;
	247
	248	/*
	249	* Case 4: Service time is equal. Choose higher throughput path.
	250	*/
	251	return pi2->relative_throughput - pi1->relative_throughput;
	252	}
	253
	254	static struct dm_path st_select_path(struct path_selector ps,
	255	unsigned *repeat_count, size_t nr_bytes)
	256	{
	257	struct selector *s = ps->context;
	258	struct path_info pi = NULL, best = NULL;
	259
	260	if (list_empty(&s->valid_paths))
	261	return NULL;
	262
	263	/* Change preferred (first in list) path to evenly balance. */
	264	list_move_tail(s->valid_paths.next, &s->valid_paths);
	265
	266	list_for_each_entry(pi, &s->valid_paths, list)
	267	if (!best \|\| (st_compare_load(pi, best, nr_bytes) < 0))
	268	best = pi;
	269
	270	if (!best)
	271	return NULL;
	272
	273	*repeat_count = best->repeat_count;
	274
	275	return best->path;
	276	}
	277
	278	static int st_start_io(struct path_selector ps, struct dm_path path,
	279	size_t nr_bytes)
	280	{
	281	struct path_info *pi = path->pscontext;
	282
	283	atomic_add(nr_bytes, &pi->in_flight_size);
	284
	285	return 0;
	286	}
	287
	288	static int st_end_io(struct path_selector ps, struct dm_path path,
	289	size_t nr_bytes)
	290	{
	291	struct path_info *pi = path->pscontext;
	292
	293	atomic_sub(nr_bytes, &pi->in_flight_size);
	294
	295	return 0;
	296	}
	297
	298	static struct path_selector_type st_ps = {
	299	.name = "service-time",
	300	.module = THIS_MODULE,
	301	.table_args = 2,
	302	.info_args = 2,
	303	.create = st_create,
	304	.destroy = st_destroy,
	305	.status = st_status,
	306	.add_path = st_add_path,
	307	.fail_path = st_fail_path,
	308	.reinstate_path = st_reinstate_path,
	309	.select_path = st_select_path,
	310	.start_io = st_start_io,
	311	.end_io = st_end_io,
	312	};
	313
	314	static int __init dm_st_init(void)
	315	{
	316	int r = dm_register_path_selector(&st_ps);
	317
	318	if (r < 0)
	319	DMERR("register failed %d", r);
	320
	321	DMINFO("version " ST_VERSION " loaded");
	322
	323	return r;
	324	}
	325
	326	static void __exit dm_st_exit(void)
	327	{
	328	int r = dm_unregister_path_selector(&st_ps);
	329
	330	if (r < 0)
	331	DMERR("unregister failed %d", r);
	332	}
	333
	334	module_init(dm_st_init);
	335	module_exit(dm_st_exit);
	336
	337	MODULE_DESCRIPTION(DM_NAME " throughput oriented path selector");
	338	MODULE_AUTHOR("Kiyoshi Ueda <k-ueda@ct.jp.nec.com>");
	339	MODULE_LICENSE("GPL");