dm thin: sort the per thin deferred bios using an rb_tree
A thin-pool will allocate blocks using FIFO order for all thin devices
which share the thin-pool. Because of this simplistic allocation the
thin-pool's space can become fragmented quite easily; especially when
multiple threads are requesting blocks in parallel.
Sort each thin device's deferred_bio_list based on logical sector to
help reduce fragmentation of the thin-pool's ondisk layout.
The following tables illustrate the realized gains/potential offered by
sorting each thin device's deferred_bio_list. An "io size"-sized random
read of the device would result in "seeks/io" fragments being read, with
an average "distance/seek" between each fragment.
Data was written to a single thin device using multiple threads via
iozone (8 threads, 64K for both the block_size and io_size).
unsorted:
io size seeks/io distance/seek
--------------------------------------
4k 0.000 0b
16k 0.013 11m
64k 0.065 11m
256k 0.274 10m
1m 1.109 10m
4m 4.411 10m
16m 17.097 11m
64m 60.055 13m
256m 148.798 25m
1g 809.929 21m
sorted:
io size seeks/io distance/seek
--------------------------------------
4k 0.000 0b
16k 0.000 1g
64k 0.001 1g
256k 0.003 1g
1m 0.011 1g
4m 0.045 1g
16m 0.181 1g
64m 0.747 1011m
256m 3.299 1g
1g 14.373 1g
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>
hifive-unleashed-5.1
Mike Snitzer
parent
c140e1c4e2
commit
67324ea188
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@ -16,6 +16,7 @@
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/rbtree.h>
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#define DM_MSG_PREFIX "thin"
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@ -230,6 +231,7 @@ struct thin_c {
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spinlock_t lock;
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struct bio_list deferred_bio_list;
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struct bio_list retry_on_resume_list;
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struct rb_root sort_bio_list; /* sorted list of deferred bios */
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};
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/*----------------------------------------------------------------*/
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@ -371,6 +373,7 @@ struct dm_thin_endio_hook {
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struct dm_deferred_entry *shared_read_entry;
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struct dm_deferred_entry *all_io_entry;
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struct dm_thin_new_mapping *overwrite_mapping;
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struct rb_node rb_node;
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};
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static void requeue_bio_list(struct thin_c *tc, struct bio_list *master)
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@ -1367,12 +1370,77 @@ static int need_commit_due_to_time(struct pool *pool)
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jiffies > pool->last_commit_jiffies + COMMIT_PERIOD;
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}
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#define thin_pbd(node) rb_entry((node), struct dm_thin_endio_hook, rb_node)
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#define thin_bio(pbd) dm_bio_from_per_bio_data((pbd), sizeof(struct dm_thin_endio_hook))
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static void __thin_bio_rb_add(struct thin_c *tc, struct bio *bio)
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{
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struct rb_node **rbp, *parent;
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struct dm_thin_endio_hook *pbd;
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sector_t bi_sector = bio->bi_iter.bi_sector;
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rbp = &tc->sort_bio_list.rb_node;
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parent = NULL;
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while (*rbp) {
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parent = *rbp;
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pbd = thin_pbd(parent);
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if (bi_sector < thin_bio(pbd)->bi_iter.bi_sector)
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rbp = &(*rbp)->rb_left;
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else
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rbp = &(*rbp)->rb_right;
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}
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pbd = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
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rb_link_node(&pbd->rb_node, parent, rbp);
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rb_insert_color(&pbd->rb_node, &tc->sort_bio_list);
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}
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static void __extract_sorted_bios(struct thin_c *tc)
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{
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struct rb_node *node;
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struct dm_thin_endio_hook *pbd;
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struct bio *bio;
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for (node = rb_first(&tc->sort_bio_list); node; node = rb_next(node)) {
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pbd = thin_pbd(node);
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bio = thin_bio(pbd);
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bio_list_add(&tc->deferred_bio_list, bio);
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rb_erase(&pbd->rb_node, &tc->sort_bio_list);
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}
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WARN_ON(!RB_EMPTY_ROOT(&tc->sort_bio_list));
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}
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static void __sort_thin_deferred_bios(struct thin_c *tc)
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{
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struct bio *bio;
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struct bio_list bios;
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bio_list_init(&bios);
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bio_list_merge(&bios, &tc->deferred_bio_list);
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bio_list_init(&tc->deferred_bio_list);
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/* Sort deferred_bio_list using rb-tree */
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while ((bio = bio_list_pop(&bios)))
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__thin_bio_rb_add(tc, bio);
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/*
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* Transfer the sorted bios in sort_bio_list back to
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* deferred_bio_list to allow lockless submission of
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* all bios.
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*/
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__extract_sorted_bios(tc);
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}
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static void process_thin_deferred_bios(struct thin_c *tc)
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{
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struct pool *pool = tc->pool;
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unsigned long flags;
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struct bio *bio;
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struct bio_list bios;
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struct blk_plug plug;
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if (tc->requeue_mode) {
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requeue_bio_list(tc, &tc->deferred_bio_list);
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@ -1382,10 +1450,20 @@ static void process_thin_deferred_bios(struct thin_c *tc)
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bio_list_init(&bios);
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spin_lock_irqsave(&tc->lock, flags);
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if (bio_list_empty(&tc->deferred_bio_list)) {
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spin_unlock_irqrestore(&tc->lock, flags);
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return;
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}
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__sort_thin_deferred_bios(tc);
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bio_list_merge(&bios, &tc->deferred_bio_list);
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bio_list_init(&tc->deferred_bio_list);
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spin_unlock_irqrestore(&tc->lock, flags);
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blk_start_plug(&plug);
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while ((bio = bio_list_pop(&bios))) {
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/*
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* If we've got no free new_mapping structs, and processing
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@ -1405,6 +1483,7 @@ static void process_thin_deferred_bios(struct thin_c *tc)
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else
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pool->process_bio(tc, bio);
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}
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blk_finish_plug(&plug);
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}
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static void process_deferred_bios(struct pool *pool)
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@ -2964,7 +3043,7 @@ static struct target_type pool_target = {
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.name = "thin-pool",
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.features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE |
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DM_TARGET_IMMUTABLE,
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.version = {1, 11, 0},
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.version = {1, 12, 0},
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.module = THIS_MODULE,
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.ctr = pool_ctr,
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.dtr = pool_dtr,
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@ -3040,6 +3119,7 @@ static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
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spin_lock_init(&tc->lock);
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bio_list_init(&tc->deferred_bio_list);
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bio_list_init(&tc->retry_on_resume_list);
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tc->sort_bio_list = RB_ROOT;
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if (argc == 3) {
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r = dm_get_device(ti, argv[2], FMODE_READ, &origin_dev);
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@ -3287,7 +3367,7 @@ static int thin_iterate_devices(struct dm_target *ti,
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static struct target_type thin_target = {
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.name = "thin",
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.version = {1, 11, 0},
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.version = {1, 12, 0},
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.module = THIS_MODULE,
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.ctr = thin_ctr,
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.dtr = thin_dtr,
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