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_user_may_insert(struct pblk_rl *rl, int nr_entries)
  27 {
  28         int rb_user_cnt = atomic_read(&rl->rb_user_cnt);
  29
  30         return (!(rb_user_cnt + nr_entries > rl->rb_user_max));
  31 }
  32
  33 int pblk_rl_gc_may_insert(struct pblk_rl *rl, int nr_entries)
  34 {
  35         int rb_gc_cnt = atomic_read(&rl->rb_gc_cnt);
  36         int rb_user_active;
  37
  38         /* If there is no user I/O let GC take over space on the write buffer */
  39         rb_user_active = READ_ONCE(rl->rb_user_active);
  40         return (!(rb_gc_cnt + nr_entries > rl->rb_gc_max && rb_user_active));
  41 }
  42
  43 void pblk_rl_user_in(struct pblk_rl *rl, int nr_entries)
  44 {
  45         atomic_add(nr_entries, &rl->rb_user_cnt);
  46
  47         /* Release user I/O state. Protect from GC */
  48         smp_store_release(&rl->rb_user_active, 1);
  49         pblk_rl_kick_u_timer(rl);
  50 }
  51
  52 void pblk_rl_gc_in(struct pblk_rl *rl, int nr_entries)
  53 {
  54         atomic_add(nr_entries, &rl->rb_gc_cnt);
  55 }
  56
  57 void pblk_rl_out(struct pblk_rl *rl, int nr_user, int nr_gc)
  58 {
  59         atomic_sub(nr_user, &rl->rb_user_cnt);
  60         atomic_sub(nr_gc, &rl->rb_gc_cnt);
  61 }
  62
  63 unsigned long pblk_rl_nr_free_blks(struct pblk_rl *rl)
  64 {
  65         return atomic_read(&rl->free_blocks);
  66 }
  67
  68 /*
  69  * We check for (i) the number of free blocks in the current LUN and (ii) the
  70  * total number of free blocks in the pblk instance. This is to even out the
  71  * number of free blocks on each LUN when GC kicks in.
  72  *
  73  * Only the total number of free blocks is used to configure the rate limiter.
  74  */
  75 static int pblk_rl_update_rates(struct pblk_rl *rl, unsigned long max)
  76 {
  77         unsigned long free_blocks = pblk_rl_nr_free_blks(rl);
  78
  79         if (free_blocks >= rl->high) {
  80                 rl->rb_user_max = max - rl->rb_gc_rsv;
  81                 rl->rb_gc_max = rl->rb_gc_rsv;
  82                 rl->rb_state = PBLK_RL_HIGH;
  83         } else if (free_blocks < rl->high) {
  84                 int shift = rl->high_pw - rl->rb_windows_pw;
  85                 int user_windows = free_blocks >> shift;
  86                 int user_max = user_windows << PBLK_MAX_REQ_ADDRS_PW;
  87                 int gc_max;
  88
  89                 rl->rb_user_max = user_max;
  90                 gc_max = max - rl->rb_user_max;
  91                 rl->rb_gc_max = max(gc_max, rl->rb_gc_rsv);
  92
  93                 if (free_blocks > rl->low)
  94                         rl->rb_state = PBLK_RL_MID;
  95                 else
  96                         rl->rb_state = PBLK_RL_LOW;
  97         }
  98
  99         return rl->rb_state;
 100 }
 101
 102 void pblk_rl_set_gc_rsc(struct pblk_rl *rl, int rsv)
 103 {
 104         rl->rb_gc_rsv = rl->rb_gc_max = rsv;
 105 }
 106
 107 void pblk_rl_free_lines_inc(struct pblk_rl *rl, struct pblk_line *line)
 108 {
 109         struct pblk *pblk = container_of(rl, struct pblk, rl);
 110         int blk_in_line = atomic_read(&line->blk_in_line);
 111         int ret;
 112
 113         atomic_add(blk_in_line, &rl->free_blocks);
 114         /* Rates will not change that often - no need to lock update */
 115         ret = pblk_rl_update_rates(rl, rl->rb_budget);
 116
 117         if (ret == (PBLK_RL_MID | PBLK_RL_LOW))
 118                 pblk_gc_should_start(pblk);
 119         else
 120                 pblk_gc_should_stop(pblk);
 121 }
 122
 123 void pblk_rl_free_lines_dec(struct pblk_rl *rl, struct pblk_line *line)
 124 {
 125         struct pblk *pblk = container_of(rl, struct pblk, rl);
 126         int blk_in_line = atomic_read(&line->blk_in_line);
 127         int ret;
 128
 129         atomic_sub(blk_in_line, &rl->free_blocks);
 130
 131         /* Rates will not change that often - no need to lock update */
 132         ret = pblk_rl_update_rates(rl, rl->rb_budget);
 133         if (ret == (PBLK_RL_MID | PBLK_RL_LOW))
 134                 pblk_gc_should_start(pblk);
 135         else
 136                 pblk_gc_should_stop(pblk);
 137 }
 138
 139 int pblk_rl_gc_thrs(struct pblk_rl *rl)
 140 {
 141         return rl->high;
 142 }
 143
 144 int pblk_rl_sysfs_rate_show(struct pblk_rl *rl)
 145 {
 146         return rl->rb_user_max;
 147 }
 148
 149 static void pblk_rl_u_timer(unsigned long data)
 150 {
 151         struct pblk_rl *rl = (struct pblk_rl *)data;
 152
 153         /* Release user I/O state. Protect from GC */
 154         smp_store_release(&rl->rb_user_active, 0);
 155 }
 156
 157 void pblk_rl_free(struct pblk_rl *rl)
 158 {
 159         del_timer(&rl->u_timer);
 160 }
 161
 162 void pblk_rl_init(struct pblk_rl *rl, int budget)
 163 {
 164         unsigned int rb_windows;
 165
 166         rl->high = rl->total_blocks / PBLK_USER_HIGH_THRS;
 167         rl->low = rl->total_blocks / PBLK_USER_LOW_THRS;
 168         rl->high_pw = get_count_order(rl->high);
 169
 170         /* This will always be a power-of-2 */
 171         rb_windows = budget / PBLK_MAX_REQ_ADDRS;
 172         rl->rb_windows_pw = get_count_order(rb_windows) + 1;
 173
 174         /* To start with, all buffer is available to user I/O writers */
 175         rl->rb_budget = budget;
 176         rl->rb_user_max = budget;
 177         atomic_set(&rl->rb_user_cnt, 0);
 178         rl->rb_gc_max = 0;
 179         rl->rb_state = PBLK_RL_HIGH;
 180         atomic_set(&rl->rb_gc_cnt, 0);
 181
 182         setup_timer(&rl->u_timer, pblk_rl_u_timer, (unsigned long)rl);
 183         rl->rb_user_active = 0;
 184 }