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/*
* Copyright (C) 2016 CNEX Labs
* Initial release: Javier Gonzalez <javier@cnexlabs.com>
* Matias Bjorling <matias@cnexlabs.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version
* 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* pblk-rl.c - pblk's rate limiter for user I/O
*
*/
#include "pblk.h"
static void pblk_rl_kick_u_timer(struct pblk_rl *rl)
{
mod_timer(&rl->u_timer, jiffies + msecs_to_jiffies(5000));
}
int pblk_rl_user_may_insert(struct pblk_rl *rl, int nr_entries)
{
int rb_user_cnt = atomic_read(&rl->rb_user_cnt);
return (!(rb_user_cnt + nr_entries > rl->rb_user_max));
}
int pblk_rl_gc_may_insert(struct pblk_rl *rl, int nr_entries)
{
int rb_gc_cnt = atomic_read(&rl->rb_gc_cnt);
int rb_user_active;
/* If there is no user I/O let GC take over space on the write buffer */
rb_user_active = READ_ONCE(rl->rb_user_active);
return (!(rb_gc_cnt + nr_entries > rl->rb_gc_max && rb_user_active));
}
void pblk_rl_user_in(struct pblk_rl *rl, int nr_entries)
{
atomic_add(nr_entries, &rl->rb_user_cnt);
/* Release user I/O state. Protect from GC */
smp_store_release(&rl->rb_user_active, 1);
pblk_rl_kick_u_timer(rl);
}
void pblk_rl_gc_in(struct pblk_rl *rl, int nr_entries)
{
atomic_add(nr_entries, &rl->rb_gc_cnt);
}
void pblk_rl_out(struct pblk_rl *rl, int nr_user, int nr_gc)
{
atomic_sub(nr_user, &rl->rb_user_cnt);
atomic_sub(nr_gc, &rl->rb_gc_cnt);
}
unsigned long pblk_rl_nr_free_blks(struct pblk_rl *rl)
{
return atomic_read(&rl->free_blocks);
}
/*
* We check for (i) the number of free blocks in the current LUN and (ii) the
* total number of free blocks in the pblk instance. This is to even out the
* number of free blocks on each LUN when GC kicks in.
*
* Only the total number of free blocks is used to configure the rate limiter.
*/
static int pblk_rl_update_rates(struct pblk_rl *rl, unsigned long max)
{
unsigned long free_blocks = pblk_rl_nr_free_blks(rl);
if (free_blocks >= rl->high) {
rl->rb_user_max = max - rl->rb_gc_rsv;
rl->rb_gc_max = rl->rb_gc_rsv;
rl->rb_state = PBLK_RL_HIGH;
} else if (free_blocks < rl->high) {
int shift = rl->high_pw - rl->rb_windows_pw;
int user_windows = free_blocks >> shift;
int user_max = user_windows << PBLK_MAX_REQ_ADDRS_PW;
int gc_max;
rl->rb_user_max = user_max;
gc_max = max - rl->rb_user_max;
rl->rb_gc_max = max(gc_max, rl->rb_gc_rsv);
if (free_blocks > rl->low)
rl->rb_state = PBLK_RL_MID;
else
rl->rb_state = PBLK_RL_LOW;
}
return rl->rb_state;
}
void pblk_rl_set_gc_rsc(struct pblk_rl *rl, int rsv)
{
rl->rb_gc_rsv = rl->rb_gc_max = rsv;
}
void pblk_rl_free_lines_inc(struct pblk_rl *rl, struct pblk_line *line)
{
struct pblk *pblk = container_of(rl, struct pblk, rl);
int ret;
atomic_add(line->blk_in_line, &rl->free_blocks);
/* Rates will not change that often - no need to lock update */
ret = pblk_rl_update_rates(rl, rl->rb_budget);
if (ret == (PBLK_RL_MID | PBLK_RL_LOW))
pblk_gc_should_start(pblk);
else
pblk_gc_should_stop(pblk);
}
void pblk_rl_free_lines_dec(struct pblk_rl *rl, struct pblk_line *line)
{
struct pblk *pblk = container_of(rl, struct pblk, rl);
int ret;
atomic_sub(line->blk_in_line, &rl->free_blocks);
/* Rates will not change that often - no need to lock update */
ret = pblk_rl_update_rates(rl, rl->rb_budget);
if (ret == (PBLK_RL_MID | PBLK_RL_LOW))
pblk_gc_should_start(pblk);
else
pblk_gc_should_stop(pblk);
}
int pblk_rl_gc_thrs(struct pblk_rl *rl)
{
return rl->high;
}
int pblk_rl_sysfs_rate_show(struct pblk_rl *rl)
{
return rl->rb_user_max;
}
static void pblk_rl_u_timer(unsigned long data)
{
struct pblk_rl *rl = (struct pblk_rl *)data;
/* Release user I/O state. Protect from GC */
smp_store_release(&rl->rb_user_active, 0);
}
void pblk_rl_free(struct pblk_rl *rl)
{
del_timer(&rl->u_timer);
}
void pblk_rl_init(struct pblk_rl *rl, int budget)
{
unsigned int rb_windows;
rl->high = rl->total_blocks / PBLK_USER_HIGH_THRS;
rl->low = rl->total_blocks / PBLK_USER_LOW_THRS;
rl->high_pw = get_count_order(rl->high);
/* This will always be a power-of-2 */
rb_windows = budget / PBLK_MAX_REQ_ADDRS;
rl->rb_windows_pw = get_count_order(rb_windows) + 1;
/* To start with, all buffer is available to user I/O writers */
rl->rb_budget = budget;
rl->rb_user_max = budget;
atomic_set(&rl->rb_user_cnt, 0);
rl->rb_gc_max = 0;
rl->rb_state = PBLK_RL_HIGH;
atomic_set(&rl->rb_gc_cnt, 0);
setup_timer(&rl->u_timer, pblk_rl_u_timer, (unsigned long)rl);
rl->rb_user_active = 0;
}
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