src/patches/suse-2.6.27.25/patches.suse/dm-mpath-queue-length-load-balancing

   1 From: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
   2 Subject: dm-mpath: add queue-length dynamic load balancer
   3 References: FATE#303862,FATE#302108
   4
   5 This patch adds a dynamic load balancer, dm-queue-length, which
   6 balances the number of in-flight I/Os.
   7
   8 The code is based on the patch posted by Stefan Bader:
   9 https://www.redhat.com/archives/dm-devel/2005-October/msg00050.html
  10
  11
  12 Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
  13 Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
  14 Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
  15 Signed-off-by: Hannes Reinecke <hare@suse.de>
  16
  17 Index: linux-2.6.27/drivers/md/Makefile
  18 ===================================================================
  19 --- linux-2.6.27.orig/drivers/md/Makefile
  20 +++ linux-2.6.27/drivers/md/Makefile
  21 @@ -32,7 +32,8 @@ obj-$(CONFIG_BLK_DEV_MD)      += md-mod.o
  22  obj-$(CONFIG_BLK_DEV_DM)       += dm-mod.o
  23  obj-$(CONFIG_DM_CRYPT)         += dm-crypt.o
  24  obj-$(CONFIG_DM_DELAY)         += dm-delay.o
  25 -obj-$(CONFIG_DM_MULTIPATH)     += dm-multipath.o dm-round-robin.o dm-least-pending.o
  26 +obj-$(CONFIG_DM_MULTIPATH)     += dm-multipath.o dm-round-robin.o \
  27 +                                  dm-least-pending.o dm-queue-length.o
  28  obj-$(CONFIG_DM_SNAPSHOT)      += dm-snapshot.o
  29  obj-$(CONFIG_DM_MIRROR)                += dm-mirror.o dm-regions.o dm-log.o
  30  obj-$(CONFIG_DM_RAID45)                += dm-raid45.o dm-log.o dm-memcache.o \
  31 Index: linux-2.6.27/drivers/md/dm-queue-length.c
  32 ===================================================================
  33 --- /dev/null
  34 +++ linux-2.6.27/drivers/md/dm-queue-length.c
  35 @@ -0,0 +1,257 @@
  36 +/*
  37 + * Copyright (C) 2004-2005 IBM Corp.  All Rights Reserved.
  38 + * Copyright (C) 2006-2008 NEC Corporation.
  39 + *
  40 + * dm-queue-length.c
  41 + *
  42 + * Module Author: Stefan Bader, IBM
  43 + * Modified by: Kiyoshi Ueda, NEC
  44 + *
  45 + * This file is released under the GPL.
  46 + *
  47 + * Load balancing path selector.
  48 + */
  49 +
  50 +#include "dm.h"
  51 +#include "dm-path-selector.h"
  52 +
  53 +#include <linux/slab.h>
  54 +#include <linux/ctype.h>
  55 +#include <linux/errno.h>
  56 +#include <linux/module.h>
  57 +#include <asm/atomic.h>
  58 +
  59 +#define DM_MSG_PREFIX  "multipath queue-length"
  60 +#define QL_MIN_IO      128
  61 +#define QL_VERSION     "0.1.0"
  62 +
  63 +struct selector {
  64 +       struct list_head        valid_paths;
  65 +       struct list_head        failed_paths;
  66 +};
  67 +
  68 +struct path_info {
  69 +       struct list_head        list;
  70 +       struct dm_path          *path;
  71 +       unsigned int            repeat_count;
  72 +       atomic_t                qlen;
  73 +};
  74 +
  75 +static struct selector *alloc_selector(void)
  76 +{
  77 +       struct selector *s = kzalloc(sizeof(*s), GFP_KERNEL);
  78 +
  79 +       if (s) {
  80 +               INIT_LIST_HEAD(&s->valid_paths);
  81 +               INIT_LIST_HEAD(&s->failed_paths);
  82 +       }
  83 +
  84 +       return s;
  85 +}
  86 +
  87 +static int ql_create(struct path_selector *ps, unsigned argc, char **argv)
  88 +{
  89 +       struct selector *s = alloc_selector();
  90 +
  91 +       if (!s)
  92 +               return -ENOMEM;
  93 +
  94 +       ps->context = s;
  95 +
  96 +       return 0;
  97 +}
  98 +
  99 +static void ql_free_paths(struct list_head *paths)
 100 +{
 101 +       struct path_info *cpi, *npi;
 102 +
 103 +       list_for_each_entry_safe(cpi, npi, paths, list) {
 104 +               list_del(&cpi->list);
 105 +               cpi->path->pscontext = NULL;
 106 +               kfree(cpi);
 107 +       }
 108 +}
 109 +
 110 +static void ql_destroy(struct path_selector *ps)
 111 +{
 112 +       struct selector *s = (struct selector *) ps->context;
 113 +
 114 +       ql_free_paths(&s->valid_paths);
 115 +       ql_free_paths(&s->failed_paths);
 116 +       kfree(s);
 117 +       ps->context = NULL;
 118 +}
 119 +
 120 +static int ql_add_path(struct path_selector *ps, struct dm_path *path,
 121 +                      int argc, char **argv, char **error)
 122 +{
 123 +       struct selector *s = (struct selector *) ps->context;
 124 +       struct path_info *pi;
 125 +       unsigned int repeat_count = QL_MIN_IO;
 126 +
 127 +       /* Parse the arguments */
 128 +       if (argc > 1) {
 129 +               *error = "queue-length ps: incorrect number of arguments";
 130 +               return -EINVAL;
 131 +       }
 132 +
 133 +       /* First path argument is number of I/Os before switching path. */
 134 +       if ((argc == 1) && (sscanf(argv[0], "%u", &repeat_count) != 1)) {
 135 +               *error = "queue-length ps: invalid repeat count";
 136 +               return -EINVAL;
 137 +       }
 138 +
 139 +       /* Allocate the path information structure */
 140 +       pi = kmalloc(sizeof(*pi), GFP_KERNEL);
 141 +       if (!pi) {
 142 +               *error = "queue-length ps: Error allocating path information";
 143 +               return -ENOMEM;
 144 +       }
 145 +
 146 +       pi->path = path;
 147 +       pi->repeat_count = repeat_count;
 148 +       atomic_set(&pi->qlen, 0);
 149 +       path->pscontext = pi;
 150 +
 151 +       list_add_tail(&pi->list, &s->valid_paths);
 152 +
 153 +       return 0;
 154 +}
 155 +
 156 +static void ql_fail_path(struct path_selector *ps, struct dm_path *path)
 157 +{
 158 +       struct selector *s = (struct selector *) ps->context;
 159 +       struct path_info *pi = path->pscontext;
 160 +
 161 +       list_move(&pi->list, &s->failed_paths);
 162 +}
 163 +
 164 +static int ql_reinstate_path(struct path_selector *ps, struct dm_path *path)
 165 +{
 166 +       struct selector *s = (struct selector *) ps->context;
 167 +       struct path_info *pi = path->pscontext;
 168 +
 169 +       list_move_tail(&pi->list, &s->valid_paths);
 170 +
 171 +       return 0;
 172 +}
 173 +
 174 +static inline int ql_compare_qlen(struct path_info *pi1, struct path_info *pi2)
 175 +{
 176 +       return atomic_read(&pi1->qlen) - atomic_read(&pi2->qlen);
 177 +}
 178 +
 179 +static struct dm_path *ql_select_path(struct path_selector *ps,
 180 +                                     unsigned *repeat_count)
 181 +{
 182 +       struct selector *s = (struct selector *) ps->context;
 183 +       struct path_info *cpi = NULL, *spi = NULL;
 184 +
 185 +       if (list_empty(&s->valid_paths))
 186 +               return NULL;
 187 +
 188 +       /* Change preferred (first in list) path to evenly balance. */
 189 +       list_move_tail(s->valid_paths.next, &s->valid_paths);
 190 +
 191 +       list_for_each_entry(cpi, &s->valid_paths, list) {
 192 +               if (!spi)
 193 +                       spi = cpi;
 194 +               else if (ql_compare_qlen(cpi, spi) < 0)
 195 +                       spi = cpi;
 196 +       }
 197 +
 198 +       if (spi)
 199 +               *repeat_count = spi->repeat_count;
 200 +
 201 +       return spi ? spi->path : NULL;
 202 +}
 203 +
 204 +static int ql_start_io(struct path_selector *ps, struct dm_path *path)
 205 +{
 206 +       struct path_info *pi = path->pscontext;
 207 +
 208 +       atomic_inc(&pi->qlen);
 209 +
 210 +       return 0;
 211 +}
 212 +
 213 +static int ql_end_io(struct path_selector *ps, struct dm_path *path)
 214 +{
 215 +       struct path_info *pi = path->pscontext;
 216 +
 217 +       atomic_dec(&pi->qlen);
 218 +
 219 +       return 0;
 220 +}
 221 +
 222 +static int ql_status(struct path_selector *ps, struct dm_path *path,
 223 +                    status_type_t type, char *result, unsigned int maxlen)
 224 +{
 225 +       int sz = 0;
 226 +       struct path_info *pi;
 227 +
 228 +       /* When called with (path == NULL), return selector status/args. */
 229 +       if (!path)
 230 +               DMEMIT("0 ");
 231 +       else {
 232 +               pi = path->pscontext;
 233 +
 234 +               switch (type) {
 235 +               case STATUSTYPE_INFO:
 236 +                       DMEMIT("%u ", atomic_read(&pi->qlen));
 237 +                       break;
 238 +               case STATUSTYPE_TABLE:
 239 +                       DMEMIT("%u ", pi->repeat_count);
 240 +                       break;
 241 +               }
 242 +       }
 243 +
 244 +       return sz;
 245 +}
 246 +
 247 +static struct path_selector_type ql_ps = {
 248 +       .name           = "queue-length",
 249 +       .module         = THIS_MODULE,
 250 +       .table_args     = 1,
 251 +       .info_args      = 1,
 252 +       .create         = ql_create,
 253 +       .destroy        = ql_destroy,
 254 +       .status         = ql_status,
 255 +       .add_path       = ql_add_path,
 256 +       .fail_path      = ql_fail_path,
 257 +       .reinstate_path = ql_reinstate_path,
 258 +       .select_path    = ql_select_path,
 259 +       .start_io       = ql_start_io,
 260 +       .end_io         = ql_end_io,
 261 +};
 262 +
 263 +static int __init dm_ql_init(void)
 264 +{
 265 +       int r = dm_register_path_selector(&ql_ps);
 266 +
 267 +       if (r < 0)
 268 +               DMERR("register failed %d", r);
 269 +
 270 +       DMINFO("version " QL_VERSION " loaded");
 271 +
 272 +       return r;
 273 +}
 274 +
 275 +static void __exit dm_ql_exit(void)
 276 +{
 277 +       int r = dm_unregister_path_selector(&ql_ps);
 278 +
 279 +       if (r < 0)
 280 +               DMERR("unregister failed %d", r);
 281 +}
 282 +
 283 +module_init(dm_ql_init);
 284 +module_exit(dm_ql_exit);
 285 +
 286 +MODULE_AUTHOR("Stefan Bader <Stefan.Bader at de.ibm.com>");
 287 +MODULE_DESCRIPTION(
 288 +       "(C) Copyright IBM Corp. 2004,2005   All Rights Reserved.\n"
 289 +       DM_NAME " load balancing path selector (dm-queue-length.c version "
 290 +       QL_VERSION ")"
 291 +);
 292 +MODULE_LICENSE("GPL");