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 void pblk_rl_update_rates(struct pblk_rl *rl)
 100 {
 101         struct pblk *pblk = container_of(rl, struct pblk, rl);
 102         unsigned long free_blocks = pblk_rl_nr_free_blks(rl);
 103         int max = rl->rb_budget;
 104
 105         if (free_blocks >= rl->high) {
 106                 rl->rb_user_max = max;
 107                 rl->rb_gc_max = 0;
 108                 rl->rb_state = PBLK_RL_HIGH;
 109         } else if (free_blocks < rl->high) {
 110                 int shift = rl->high_pw - rl->rb_windows_pw;
 111                 int user_windows = free_blocks >> shift;
 112                 int user_max = user_windows << PBLK_MAX_REQ_ADDRS_PW;
 113
 114                 rl->rb_user_max = user_max;
 115                 rl->rb_gc_max = max - user_max;
 116
 117                 if (free_blocks <= rl->rsv_blocks) {
 118                         rl->rb_user_max = 0;
 119                         rl->rb_gc_max = max;
 120                 }
 121
 122                 /* In the worst case, we will need to GC lines in the low list
 123                  * (high valid sector count). If there are lines to GC on high
 124                  * or mid lists, these will be prioritized
 125                  */
 126                 rl->rb_state = PBLK_RL_LOW;
 127         }
 128
 129         if (rl->rb_state == (PBLK_RL_MID | PBLK_RL_LOW))
 130                 pblk_gc_should_start(pblk);
 131         else
 132                 pblk_gc_should_stop(pblk);
 133 }
 134
 135 void pblk_rl_free_lines_inc(struct pblk_rl *rl, struct pblk_line *line)
 136 {
 137         int blk_in_line = atomic_read(&line->blk_in_line);
 138
 139         atomic_add(blk_in_line, &rl->free_blocks);
 140         pblk_rl_update_rates(rl);
 141 }
 142
 143 void pblk_rl_free_lines_dec(struct pblk_rl *rl, struct pblk_line *line)
 144 {
 145         int blk_in_line = atomic_read(&line->blk_in_line);
 146
 147         atomic_sub(blk_in_line, &rl->free_blocks);
 148         pblk_rl_update_rates(rl);
 149 }
 150
 151 int pblk_rl_high_thrs(struct pblk_rl *rl)
 152 {
 153         return rl->high;
 154 }
 155
 156 int pblk_rl_max_io(struct pblk_rl *rl)
 157 {
 158         return rl->rb_max_io;
 159 }
 160
 161 static void pblk_rl_u_timer(struct timer_list *t)
 162 {
 163         struct pblk_rl *rl = from_timer(rl, t, u_timer);
 164
 165         /* Release user I/O state. Protect from GC */
 166         smp_store_release(&rl->rb_user_active, 0);
 167 }
 168
 169 void pblk_rl_free(struct pblk_rl *rl)
 170 {
 171         del_timer(&rl->u_timer);
 172 }
 173
 174 void pblk_rl_init(struct pblk_rl *rl, int budget)
 175 {
 176         struct pblk *pblk = container_of(rl, struct pblk, rl);
 177         struct pblk_line_meta *lm = &pblk->lm;
 178         int min_blocks = lm->blk_per_line * PBLK_GC_RSV_LINE;
 179         unsigned int rb_windows;
 180
 181         rl->high = rl->total_blocks / PBLK_USER_HIGH_THRS;
 182         rl->high_pw = get_count_order(rl->high);
 183
 184         rl->low = rl->total_blocks / PBLK_USER_LOW_THRS;
 185         if (rl->low < min_blocks)
 186                 rl->low = min_blocks;
 187
 188         rl->rsv_blocks = min_blocks;
 189
 190         /* This will always be a power-of-2 */
 191         rb_windows = budget / PBLK_MAX_REQ_ADDRS;
 192         rl->rb_windows_pw = get_count_order(rb_windows);
 193
 194         /* To start with, all buffer is available to user I/O writers */
 195         rl->rb_budget = budget;
 196         rl->rb_user_max = budget;
 197         rl->rb_max_io = budget >> 1;
 198         rl->rb_gc_max = 0;
 199         rl->rb_state = PBLK_RL_HIGH;
 200
 201         atomic_set(&rl->rb_user_cnt, 0);
 202         atomic_set(&rl->rb_gc_cnt, 0);
 203         atomic_set(&rl->rb_space, -1);
 204
 205         timer_setup(&rl->u_timer, pblk_rl_u_timer, 0);
 206
 207         rl->rb_user_active = 0;
 208         rl->rb_gc_active = 0;
 209 }