drivers/lightnvm/pblk-rl.c

   1 /*
   2  * Copyright (C) 2016 CNEX Labs
   3  * Initial release: Javier Gonzalez <javier@cnexlabs.com>
   4  *                  Matias Bjorling <matias@cnexlabs.com>
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License version
   8  * 2 as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License for more details.
  14  *
  15  * pblk-rl.c - pblk's rate limiter for user I/O
  16  *
  17  */
  18
  19 #include "pblk.h"
  20
  21 static void pblk_rl_kick_u_timer(struct pblk_rl *rl)
  22 {
  23         mod_timer(&rl->u_timer, jiffies + msecs_to_jiffies(5000));
  24 }
  25
  26 int pblk_rl_is_limit(struct pblk_rl *rl)
  27 {
  28         int rb_space;
  29
  30         rb_space = atomic_read(&rl->rb_space);
  31
  32         return (rb_space == 0);
  33 }
  34
  35 int pblk_rl_user_may_insert(struct pblk_rl *rl, int nr_entries)
  36 {
  37         int rb_user_cnt = atomic_read(&rl->rb_user_cnt);
  38         int rb_space = atomic_read(&rl->rb_space);
  39
  40         if (unlikely(rb_space >= 0) && (rb_space - nr_entries < 0))
  41                 return NVM_IO_ERR;
  42
  43         if (rb_user_cnt >= rl->rb_user_max)
  44                 return NVM_IO_REQUEUE;
  45
  46         return NVM_IO_OK;
  47 }
  48
  49 void pblk_rl_inserted(struct pblk_rl *rl, int nr_entries)
  50 {
  51         int rb_space = atomic_read(&rl->rb_space);
  52
  53         if (unlikely(rb_space >= 0))
  54                 atomic_sub(nr_entries, &rl->rb_space);
  55 }
  56
  57 int pblk_rl_gc_may_insert(struct pblk_rl *rl, int nr_entries)
  58 {
  59         int rb_gc_cnt = atomic_read(&rl->rb_gc_cnt);
  60         int rb_user_active;
  61
  62         /* If there is no user I/O let GC take over space on the write buffer */
  63         rb_user_active = READ_ONCE(rl->rb_user_active);
  64         return (!(rb_gc_cnt >= rl->rb_gc_max && rb_user_active));
  65 }
  66
  67 void pblk_rl_user_in(struct pblk_rl *rl, int nr_entries)
  68 {
  69         atomic_add(nr_entries, &rl->rb_user_cnt);
  70
  71         /* Release user I/O state. Protect from GC */
  72         smp_store_release(&rl->rb_user_active, 1);
  73         pblk_rl_kick_u_timer(rl);
  74 }
  75
  76 void pblk_rl_gc_in(struct pblk_rl *rl, int nr_entries)
  77 {
  78         atomic_add(nr_entries, &rl->rb_gc_cnt);
  79 }
  80
  81 void pblk_rl_out(struct pblk_rl *rl, int nr_user, int nr_gc)
  82 {
  83         atomic_sub(nr_user, &rl->rb_user_cnt);
  84         atomic_sub(nr_gc, &rl->rb_gc_cnt);
  85 }
  86
  87 unsigned long pblk_rl_nr_free_blks(struct pblk_rl *rl)
  88 {
  89         return atomic_read(&rl->free_blocks);
  90 }
  91
  92 /*
  93  * We check for (i) the number of free blocks in the current LUN and (ii) the
  94  * total number of free blocks in the pblk instance. This is to even out the
  95  * number of free blocks on each LUN when GC kicks in.
  96  *
  97  * Only the total number of free blocks is used to configure the rate limiter.
  98  */
  99 static int pblk_rl_update_rates(struct pblk_rl *rl, unsigned long max)
 100 {
 101         unsigned long free_blocks = pblk_rl_nr_free_blks(rl);
 102
 103         if (free_blocks >= rl->high) {
 104                 rl->rb_user_max = max;
 105                 rl->rb_gc_max = 0;
 106                 rl->rb_state = PBLK_RL_HIGH;
 107         } else if (free_blocks < rl->high) {
 108                 int shift = rl->high_pw - rl->rb_windows_pw;
 109                 int user_windows = free_blocks >> shift;
 110                 int user_max = user_windows << PBLK_MAX_REQ_ADDRS_PW;
 111
 112                 rl->rb_user_max = user_max;
 113                 rl->rb_gc_max = max - user_max;
 114
 115                 if (free_blocks <= rl->rsv_blocks) {
 116                         rl->rb_user_max = 0;
 117                         rl->rb_gc_max = max;
 118                 }
 119
 120                 /* In the worst case, we will need to GC lines in the low list
 121                  * (high valid sector count). If there are lines to GC on high
 122                  * or mid lists, these will be prioritized
 123                  */
 124                 rl->rb_state = PBLK_RL_LOW;
 125         }
 126
 127         return rl->rb_state;
 128 }
 129
 130 void pblk_rl_free_lines_inc(struct pblk_rl *rl, struct pblk_line *line)
 131 {
 132         struct pblk *pblk = container_of(rl, struct pblk, rl);
 133         int blk_in_line = atomic_read(&line->blk_in_line);
 134         int ret;
 135
 136         atomic_add(blk_in_line, &rl->free_blocks);
 137         /* Rates will not change that often - no need to lock update */
 138         ret = pblk_rl_update_rates(rl, rl->rb_budget);
 139
 140         if (ret == (PBLK_RL_MID | PBLK_RL_LOW))
 141                 pblk_gc_should_start(pblk);
 142         else
 143                 pblk_gc_should_stop(pblk);
 144 }
 145
 146 void pblk_rl_free_lines_dec(struct pblk_rl *rl, struct pblk_line *line)
 147 {
 148         int blk_in_line = atomic_read(&line->blk_in_line);
 149
 150         atomic_sub(blk_in_line, &rl->free_blocks);
 151 }
 152
 153 void pblk_gc_should_kick(struct pblk *pblk)
 154 {
 155         struct pblk_rl *rl = &pblk->rl;
 156         int ret;
 157
 158         /* Rates will not change that often - no need to lock update */
 159         ret = pblk_rl_update_rates(rl, rl->rb_budget);
 160         if (ret == (PBLK_RL_MID | PBLK_RL_LOW))
 161                 pblk_gc_should_start(pblk);
 162         else
 163                 pblk_gc_should_stop(pblk);
 164 }
 165
 166 int pblk_rl_high_thrs(struct pblk_rl *rl)
 167 {
 168         return rl->high;
 169 }
 170
 171 int pblk_rl_low_thrs(struct pblk_rl *rl)
 172 {
 173         return rl->low;
 174 }
 175
 176 int pblk_rl_sysfs_rate_show(struct pblk_rl *rl)
 177 {
 178         return rl->rb_user_max;
 179 }
 180
 181 static void pblk_rl_u_timer(unsigned long data)
 182 {
 183         struct pblk_rl *rl = (struct pblk_rl *)data;
 184
 185         /* Release user I/O state. Protect from GC */
 186         smp_store_release(&rl->rb_user_active, 0);
 187 }
 188
 189 void pblk_rl_free(struct pblk_rl *rl)
 190 {
 191         del_timer(&rl->u_timer);
 192 }
 193
 194 void pblk_rl_init(struct pblk_rl *rl, int budget)
 195 {
 196         struct pblk *pblk = container_of(rl, struct pblk, rl);
 197         struct pblk_line_meta *lm = &pblk->lm;
 198         int min_blocks = lm->blk_per_line * PBLK_GC_RSV_LINE;
 199         unsigned int rb_windows;
 200
 201         rl->high = rl->total_blocks / PBLK_USER_HIGH_THRS;
 202         rl->high_pw = get_count_order(rl->high);
 203
 204         rl->low = rl->total_blocks / PBLK_USER_LOW_THRS;
 205         if (rl->low < min_blocks)
 206                 rl->low = min_blocks;
 207
 208         rl->rsv_blocks = min_blocks;
 209
 210         /* This will always be a power-of-2 */
 211         rb_windows = budget / PBLK_MAX_REQ_ADDRS;
 212         rl->rb_windows_pw = get_count_order(rb_windows);
 213
 214         /* To start with, all buffer is available to user I/O writers */
 215         rl->rb_budget = budget;
 216         rl->rb_user_max = budget;
 217         rl->rb_gc_max = 0;
 218         rl->rb_state = PBLK_RL_HIGH;
 219
 220         atomic_set(&rl->rb_user_cnt, 0);
 221         atomic_set(&rl->rb_gc_cnt, 0);
 222         atomic_set(&rl->rb_space, -1);
 223
 224         setup_timer(&rl->u_timer, pblk_rl_u_timer, (unsigned long)rl);
 225
 226         rl->rb_user_active = 0;
 227         rl->rb_gc_active = 0;
 228 }