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b144e45fc5
When attaching a cached device (a.k.a backing device) to a cache device, bch_sectors_dirty_init() is called to count dirty sectors and stripes (see what bcache_dev_sectors_dirty_add() does) on the cache device. The counting is done by a single thread recursive function bch_btree_map_keys() to iterate all the bcache btree nodes. If the btree has huge number of nodes, bch_sectors_dirty_init() will take quite long time. In my testing, if the registering cache set has a existed UUID which matches a already registered cached device, the automatical attachment during the registration may take more than 55 minutes. This is too long for waiting the bcache to work in real deployment. Fortunately when bch_sectors_dirty_init() is called, no other thread will access the btree yet, it is safe to do a read-only parallelized dirty sectors counting by multiple threads. This patch tries to create multiple threads, and each thread tries to one-by-one count dirty sectors from the sub-tree indexed by a root node key which the thread fetched. After the sub-tree is counted, the counting thread will continue to fetch another root node key, until the fetched key is NULL. How many threads in parallel depends on the number of keys from the btree root node, and the number of online CPU core. The thread number will be the less number but no more than BCH_DIRTY_INIT_THRD_MAX. If there are only 2 keys in root node, it can only be 2x times faster by this patch. But if there are 10 keys in the root node, with this patch it can be 10x times faster. Signed-off-by: Coly Li <colyli@suse.de> Cc: Christoph Hellwig <hch@infradead.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
137 lines
3.3 KiB
C
137 lines
3.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _BCACHE_WRITEBACK_H
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#define _BCACHE_WRITEBACK_H
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#define CUTOFF_WRITEBACK 40
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#define CUTOFF_WRITEBACK_SYNC 70
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#define CUTOFF_WRITEBACK_MAX 70
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#define CUTOFF_WRITEBACK_SYNC_MAX 90
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#define MAX_WRITEBACKS_IN_PASS 5
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#define MAX_WRITESIZE_IN_PASS 5000 /* *512b */
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#define WRITEBACK_RATE_UPDATE_SECS_MAX 60
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#define WRITEBACK_RATE_UPDATE_SECS_DEFAULT 5
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#define BCH_AUTO_GC_DIRTY_THRESHOLD 50
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#define BCH_DIRTY_INIT_THRD_MAX 64
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/*
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* 14 (16384ths) is chosen here as something that each backing device
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* should be a reasonable fraction of the share, and not to blow up
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* until individual backing devices are a petabyte.
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*/
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#define WRITEBACK_SHARE_SHIFT 14
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struct bch_dirty_init_state;
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struct dirty_init_thrd_info {
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struct bch_dirty_init_state *state;
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struct task_struct *thread;
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};
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struct bch_dirty_init_state {
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struct cache_set *c;
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struct bcache_device *d;
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int total_threads;
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int key_idx;
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spinlock_t idx_lock;
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atomic_t started;
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atomic_t enough;
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wait_queue_head_t wait;
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struct dirty_init_thrd_info infos[BCH_DIRTY_INIT_THRD_MAX];
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};
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static inline uint64_t bcache_dev_sectors_dirty(struct bcache_device *d)
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{
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uint64_t i, ret = 0;
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for (i = 0; i < d->nr_stripes; i++)
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ret += atomic_read(d->stripe_sectors_dirty + i);
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return ret;
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}
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static inline unsigned int offset_to_stripe(struct bcache_device *d,
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uint64_t offset)
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{
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do_div(offset, d->stripe_size);
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return offset;
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}
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static inline bool bcache_dev_stripe_dirty(struct cached_dev *dc,
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uint64_t offset,
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unsigned int nr_sectors)
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{
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unsigned int stripe = offset_to_stripe(&dc->disk, offset);
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while (1) {
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if (atomic_read(dc->disk.stripe_sectors_dirty + stripe))
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return true;
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if (nr_sectors <= dc->disk.stripe_size)
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return false;
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nr_sectors -= dc->disk.stripe_size;
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stripe++;
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}
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}
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extern unsigned int bch_cutoff_writeback;
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extern unsigned int bch_cutoff_writeback_sync;
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static inline bool should_writeback(struct cached_dev *dc, struct bio *bio,
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unsigned int cache_mode, bool would_skip)
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{
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unsigned int in_use = dc->disk.c->gc_stats.in_use;
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if (cache_mode != CACHE_MODE_WRITEBACK ||
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test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
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in_use > bch_cutoff_writeback_sync)
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return false;
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if (bio_op(bio) == REQ_OP_DISCARD)
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return false;
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if (dc->partial_stripes_expensive &&
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bcache_dev_stripe_dirty(dc, bio->bi_iter.bi_sector,
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bio_sectors(bio)))
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return true;
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if (would_skip)
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return false;
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return (op_is_sync(bio->bi_opf) ||
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bio->bi_opf & (REQ_META|REQ_PRIO) ||
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in_use <= bch_cutoff_writeback);
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}
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static inline void bch_writeback_queue(struct cached_dev *dc)
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{
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if (!IS_ERR_OR_NULL(dc->writeback_thread))
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wake_up_process(dc->writeback_thread);
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}
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static inline void bch_writeback_add(struct cached_dev *dc)
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{
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if (!atomic_read(&dc->has_dirty) &&
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!atomic_xchg(&dc->has_dirty, 1)) {
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if (BDEV_STATE(&dc->sb) != BDEV_STATE_DIRTY) {
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SET_BDEV_STATE(&dc->sb, BDEV_STATE_DIRTY);
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/* XXX: should do this synchronously */
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bch_write_bdev_super(dc, NULL);
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}
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bch_writeback_queue(dc);
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}
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}
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void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned int inode,
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uint64_t offset, int nr_sectors);
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void bch_sectors_dirty_init(struct bcache_device *d);
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void bch_cached_dev_writeback_init(struct cached_dev *dc);
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int bch_cached_dev_writeback_start(struct cached_dev *dc);
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#endif
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