This patch adds a dynamic load balancer, dm-queue-length, which balances the number of in-flight I/Os. The code is based on the patch posted by Stefan Bader: https://www.redhat.com/archives/dm-devel/2005-October/msg00050.html Signed-off-by: Stefan Bader <stefan.bader@xxxxxxxxxxxxx> Signed-off-by: Kiyoshi Ueda <k-ueda@xxxxxxxxxxxxx> Signed-off-by: Jun'ichi Nomura <j-nomura@xxxxxxxxxxxxx> --- drivers/md/Makefile | 3 drivers/md/dm-queue-length.c | 257 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 259 insertions(+), 1 deletion(-) Index: 2.6.27-rc6/drivers/md/dm-queue-length.c =================================================================== --- /dev/null +++ 2.6.27-rc6/drivers/md/dm-queue-length.c @@ -0,0 +1,257 @@ +/* + * Copyright (C) 2004-2005 IBM Corp. All Rights Reserved. + * Copyright (C) 2006-2008 NEC Corporation. + * + * dm-queue-length.c + * + * Module Author: Stefan Bader, IBM + * Modified by: Kiyoshi Ueda, NEC + * + * This file is released under the GPL. + * + * Load balancing path selector. + */ + +#include "dm.h" +#include "dm-path-selector.h" + +#include <linux/slab.h> +#include <linux/ctype.h> +#include <linux/errno.h> +#include <linux/module.h> +#include <asm/atomic.h> + +#define DM_MSG_PREFIX "multipath queue-length" +#define QL_MIN_IO 128 +#define QL_VERSION "0.1.0" + +struct selector { + struct list_head valid_paths; + struct list_head failed_paths; +}; + +struct path_info { + struct list_head list; + struct dm_path *path; + unsigned int repeat_count; + atomic_t qlen; +}; + +static struct selector *alloc_selector(void) +{ + struct selector *s = kzalloc(sizeof(*s), GFP_KERNEL); + + if (s) { + INIT_LIST_HEAD(&s->valid_paths); + INIT_LIST_HEAD(&s->failed_paths); + } + + return s; +} + +static int ql_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 ql_free_paths(struct list_head *paths) +{ + struct path_info *cpi, *npi; + + list_for_each_entry_safe(cpi, npi, paths, list) { + list_del(&cpi->list); + cpi->path->pscontext = NULL; + kfree(cpi); + } +} + +static void ql_destroy(struct path_selector *ps) +{ + struct selector *s = (struct selector *) ps->context; + + ql_free_paths(&s->valid_paths); + ql_free_paths(&s->failed_paths); + kfree(s); + ps->context = NULL; +} + +static int ql_add_path(struct path_selector *ps, struct dm_path *path, + int argc, char **argv, char **error) +{ + struct selector *s = (struct selector *) ps->context; + struct path_info *pi; + unsigned int repeat_count = QL_MIN_IO; + + /* Parse the arguments */ + if (argc > 1) { + *error = "queue-length ps: incorrect number of arguments"; + return -EINVAL; + } + + /* First path argument is number of I/Os before switching path. */ + if ((argc == 1) && (sscanf(argv[0], "%u", &repeat_count) != 1)) { + *error = "queue-length ps: invalid repeat count"; + return -EINVAL; + } + + /* Allocate the path information structure */ + pi = kmalloc(sizeof(*pi), GFP_KERNEL); + if (!pi) { + *error = "queue-length ps: Error allocating path information"; + return -ENOMEM; + } + + pi->path = path; + pi->repeat_count = repeat_count; + atomic_set(&pi->qlen, 0); + path->pscontext = pi; + + list_add_tail(&pi->list, &s->valid_paths); + + return 0; +} + +static void ql_fail_path(struct path_selector *ps, struct dm_path *path) +{ + struct selector *s = (struct selector *) ps->context; + struct path_info *pi = path->pscontext; + + list_move(&pi->list, &s->failed_paths); +} + +static int ql_reinstate_path(struct path_selector *ps, struct dm_path *path) +{ + struct selector *s = (struct selector *) ps->context; + struct path_info *pi = path->pscontext; + + list_move_tail(&pi->list, &s->valid_paths); + + return 0; +} + +static inline int ql_compare_qlen(struct path_info *pi1, struct path_info *pi2) +{ + return atomic_read(&pi1->qlen) - atomic_read(&pi2->qlen); +} + +static struct dm_path *ql_select_path(struct path_selector *ps, + unsigned *repeat_count) +{ + struct selector *s = (struct selector *) ps->context; + struct path_info *cpi = NULL, *spi = 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(cpi, &s->valid_paths, list) { + if (!spi) + spi = cpi; + else if (ql_compare_qlen(cpi, spi) < 0) + spi = cpi; + } + + if (spi) + *repeat_count = spi->repeat_count; + + return spi ? spi->path : NULL; +} + +static int ql_start_io(struct path_selector *ps, struct dm_path *path) +{ + struct path_info *pi = path->pscontext; + + atomic_inc(&pi->qlen); + + return 0; +} + +static int ql_end_io(struct path_selector *ps, struct dm_path *path) +{ + struct path_info *pi = path->pscontext; + + atomic_dec(&pi->qlen); + + return 0; +} + +static int ql_status(struct path_selector *ps, struct dm_path *path, + status_type_t type, char *result, unsigned int maxlen) +{ + int sz = 0; + struct path_info *pi; + + /* When called with (path == NULL), return selector status/args. */ + if (!path) + DMEMIT("0 "); + else { + pi = path->pscontext; + + switch (type) { + case STATUSTYPE_INFO: + DMEMIT("%u ", atomic_read(&pi->qlen)); + break; + case STATUSTYPE_TABLE: + DMEMIT("%u ", pi->repeat_count); + break; + } + } + + return sz; +} + +static struct path_selector_type ql_ps = { + .name = "queue-length", + .module = THIS_MODULE, + .table_args = 1, + .info_args = 1, + .create = ql_create, + .destroy = ql_destroy, + .status = ql_status, + .add_path = ql_add_path, + .fail_path = ql_fail_path, + .reinstate_path = ql_reinstate_path, + .select_path = ql_select_path, + .start_io = ql_start_io, + .end_io = ql_end_io, +}; + +static int __init dm_ql_init(void) +{ + int r = dm_register_path_selector(&ql_ps); + + if (r < 0) + DMERR("register failed %d", r); + + DMINFO("version " QL_VERSION " loaded"); + + return r; +} + +static void __exit dm_ql_exit(void) +{ + int r = dm_unregister_path_selector(&ql_ps); + + if (r < 0) + DMERR("unregister failed %d", r); +} + +module_init(dm_ql_init); +module_exit(dm_ql_exit); + +MODULE_AUTHOR("Stefan Bader <Stefan.Bader at de.ibm.com>"); +MODULE_DESCRIPTION( + "(C) Copyright IBM Corp. 2004,2005 All Rights Reserved.\n" + DM_NAME " load balancing path selector (dm-queue-length.c version " + QL_VERSION ")" +); +MODULE_LICENSE("GPL"); Index: 2.6.27-rc6/drivers/md/Makefile =================================================================== --- 2.6.27-rc6.orig/drivers/md/Makefile +++ 2.6.27-rc6/drivers/md/Makefile @@ -32,7 +32,8 @@ obj-$(CONFIG_BLK_DEV_MD) += md-mod.o obj-$(CONFIG_BLK_DEV_DM) += dm-mod.o obj-$(CONFIG_DM_CRYPT) += dm-crypt.o obj-$(CONFIG_DM_DELAY) += dm-delay.o -obj-$(CONFIG_DM_MULTIPATH) += dm-multipath.o dm-round-robin.o +obj-$(CONFIG_DM_MULTIPATH) += dm-multipath.o dm-round-robin.o \ + dm-queue-length.o obj-$(CONFIG_DM_SNAPSHOT) += dm-snapshot.o obj-$(CONFIG_DM_MIRROR) += dm-mirror.o dm-log.o obj-$(CONFIG_DM_ZERO) += dm-zero.o -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
