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![Hans Holmberg](/assets/img/avatar_default.png)
In a worst-case scenario (random writes), OP% of sectors in each line will be invalid, and we will then need to move data out of 100/OP% lines to free a single line. So, to prevent the possibility of running out of lines, temporarily block user writes when there is less than 100/OP% free lines. Also ensure that pblk creation does not produce instances with insufficient over provisioning. Insufficient over-provising is not a problem on real hardware, but often an issue when running QEMU simulations (with few lines). 100 lines is enough to create a sane instance with the standard (11%) over provisioning. Signed-off-by: Hans Holmberg <hans.holmberg@cnexlabs.com> Reviewed-by: Javier González <javier@javigon.com> Signed-off-by: Matias Bjørling <mb@lightnvm.io> Signed-off-by: Jens Axboe <axboe@kernel.dk>
250 lines
6.1 KiB
C
250 lines
6.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2016 CNEX Labs
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* Initial release: Javier Gonzalez <javier@cnexlabs.com>
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* Matias Bjorling <matias@cnexlabs.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License version
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* 2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* pblk-rl.c - pblk's rate limiter for user I/O
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*
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*/
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#include "pblk.h"
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static void pblk_rl_kick_u_timer(struct pblk_rl *rl)
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{
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mod_timer(&rl->u_timer, jiffies + msecs_to_jiffies(5000));
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}
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int pblk_rl_is_limit(struct pblk_rl *rl)
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{
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int rb_space;
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rb_space = atomic_read(&rl->rb_space);
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return (rb_space == 0);
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}
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int pblk_rl_user_may_insert(struct pblk_rl *rl, int nr_entries)
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{
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int rb_user_cnt = atomic_read(&rl->rb_user_cnt);
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int rb_space = atomic_read(&rl->rb_space);
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if (unlikely(rb_space >= 0) && (rb_space - nr_entries < 0))
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return NVM_IO_ERR;
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if (rb_user_cnt >= rl->rb_user_max)
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return NVM_IO_REQUEUE;
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return NVM_IO_OK;
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}
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void pblk_rl_inserted(struct pblk_rl *rl, int nr_entries)
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{
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int rb_space = atomic_read(&rl->rb_space);
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if (unlikely(rb_space >= 0))
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atomic_sub(nr_entries, &rl->rb_space);
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}
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int pblk_rl_gc_may_insert(struct pblk_rl *rl, int nr_entries)
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{
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int rb_gc_cnt = atomic_read(&rl->rb_gc_cnt);
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int rb_user_active;
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/* If there is no user I/O let GC take over space on the write buffer */
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rb_user_active = READ_ONCE(rl->rb_user_active);
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return (!(rb_gc_cnt >= rl->rb_gc_max && rb_user_active));
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}
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void pblk_rl_user_in(struct pblk_rl *rl, int nr_entries)
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{
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atomic_add(nr_entries, &rl->rb_user_cnt);
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/* Release user I/O state. Protect from GC */
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smp_store_release(&rl->rb_user_active, 1);
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pblk_rl_kick_u_timer(rl);
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}
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void pblk_rl_werr_line_in(struct pblk_rl *rl)
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{
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atomic_inc(&rl->werr_lines);
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}
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void pblk_rl_werr_line_out(struct pblk_rl *rl)
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{
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atomic_dec(&rl->werr_lines);
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}
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void pblk_rl_gc_in(struct pblk_rl *rl, int nr_entries)
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{
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atomic_add(nr_entries, &rl->rb_gc_cnt);
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}
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void pblk_rl_out(struct pblk_rl *rl, int nr_user, int nr_gc)
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{
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atomic_sub(nr_user, &rl->rb_user_cnt);
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atomic_sub(nr_gc, &rl->rb_gc_cnt);
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}
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unsigned long pblk_rl_nr_free_blks(struct pblk_rl *rl)
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{
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return atomic_read(&rl->free_blocks);
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}
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unsigned long pblk_rl_nr_user_free_blks(struct pblk_rl *rl)
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{
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return atomic_read(&rl->free_user_blocks);
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}
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static void __pblk_rl_update_rates(struct pblk_rl *rl,
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unsigned long free_blocks)
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{
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struct pblk *pblk = container_of(rl, struct pblk, rl);
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int max = rl->rb_budget;
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int werr_gc_needed = atomic_read(&rl->werr_lines);
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if (free_blocks >= rl->high) {
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if (werr_gc_needed) {
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/* Allocate a small budget for recovering
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* lines with write errors
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*/
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rl->rb_gc_max = 1 << rl->rb_windows_pw;
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rl->rb_user_max = max - rl->rb_gc_max;
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rl->rb_state = PBLK_RL_WERR;
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} else {
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rl->rb_user_max = max;
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rl->rb_gc_max = 0;
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rl->rb_state = PBLK_RL_OFF;
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}
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} else if (free_blocks < rl->high) {
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int shift = rl->high_pw - rl->rb_windows_pw;
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int user_windows = free_blocks >> shift;
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int user_max = user_windows << ilog2(NVM_MAX_VLBA);
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rl->rb_user_max = user_max;
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rl->rb_gc_max = max - user_max;
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if (free_blocks <= rl->rsv_blocks) {
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rl->rb_user_max = 0;
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rl->rb_gc_max = max;
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}
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/* In the worst case, we will need to GC lines in the low list
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* (high valid sector count). If there are lines to GC on high
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* or mid lists, these will be prioritized
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*/
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rl->rb_state = PBLK_RL_LOW;
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}
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if (rl->rb_state != PBLK_RL_OFF)
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pblk_gc_should_start(pblk);
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else
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pblk_gc_should_stop(pblk);
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}
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void pblk_rl_update_rates(struct pblk_rl *rl)
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{
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__pblk_rl_update_rates(rl, pblk_rl_nr_user_free_blks(rl));
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}
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void pblk_rl_free_lines_inc(struct pblk_rl *rl, struct pblk_line *line)
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{
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int blk_in_line = atomic_read(&line->blk_in_line);
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int free_blocks;
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atomic_add(blk_in_line, &rl->free_blocks);
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free_blocks = atomic_add_return(blk_in_line, &rl->free_user_blocks);
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__pblk_rl_update_rates(rl, free_blocks);
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}
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void pblk_rl_free_lines_dec(struct pblk_rl *rl, struct pblk_line *line,
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bool used)
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{
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int blk_in_line = atomic_read(&line->blk_in_line);
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int free_blocks;
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atomic_sub(blk_in_line, &rl->free_blocks);
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if (used)
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free_blocks = atomic_sub_return(blk_in_line,
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&rl->free_user_blocks);
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else
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free_blocks = atomic_read(&rl->free_user_blocks);
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__pblk_rl_update_rates(rl, free_blocks);
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}
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int pblk_rl_high_thrs(struct pblk_rl *rl)
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{
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return rl->high;
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}
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int pblk_rl_max_io(struct pblk_rl *rl)
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{
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return rl->rb_max_io;
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}
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static void pblk_rl_u_timer(struct timer_list *t)
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{
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struct pblk_rl *rl = from_timer(rl, t, u_timer);
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/* Release user I/O state. Protect from GC */
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smp_store_release(&rl->rb_user_active, 0);
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}
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void pblk_rl_free(struct pblk_rl *rl)
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{
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del_timer(&rl->u_timer);
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}
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void pblk_rl_init(struct pblk_rl *rl, int budget)
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{
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struct pblk *pblk = container_of(rl, struct pblk, rl);
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struct nvm_tgt_dev *dev = pblk->dev;
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struct nvm_geo *geo = &dev->geo;
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struct pblk_line_mgmt *l_mg = &pblk->l_mg;
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struct pblk_line_meta *lm = &pblk->lm;
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int sec_meta, blk_meta;
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unsigned int rb_windows;
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/* Consider sectors used for metadata */
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sec_meta = (lm->smeta_sec + lm->emeta_sec[0]) * l_mg->nr_free_lines;
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blk_meta = DIV_ROUND_UP(sec_meta, geo->clba);
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rl->high = pblk->op_blks - blk_meta - lm->blk_per_line;
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rl->high_pw = get_count_order(rl->high);
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rl->rsv_blocks = pblk_get_min_chks(pblk);
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/* This will always be a power-of-2 */
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rb_windows = budget / NVM_MAX_VLBA;
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rl->rb_windows_pw = get_count_order(rb_windows);
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/* To start with, all buffer is available to user I/O writers */
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rl->rb_budget = budget;
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rl->rb_user_max = budget;
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rl->rb_max_io = budget >> 1;
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rl->rb_gc_max = 0;
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rl->rb_state = PBLK_RL_HIGH;
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atomic_set(&rl->rb_user_cnt, 0);
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atomic_set(&rl->rb_gc_cnt, 0);
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atomic_set(&rl->rb_space, -1);
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atomic_set(&rl->werr_lines, 0);
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timer_setup(&rl->u_timer, pblk_rl_u_timer, 0);
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rl->rb_user_active = 0;
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rl->rb_gc_active = 0;
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}
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