From b7a9f29fcf4e53e9ca7982331649fa2013e69c99 Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Wed, 4 Feb 2009 09:23:45 -0500 Subject: [PATCH] Btrfs: sort references by byte number during btrfs_inc_ref When a block goes through cow, we update the reference counts of everything that block points to. The internal pointers of the block can be in just about any order, and it is likely to have clusters of things that are close together and clusters of things that are not. To help reduce the seeks that come with updating all of these reference counts, sort them by byte number before actual updates are done. Signed-off-by: Chris Mason --- fs/btrfs/extent-tree.c | 85 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 79 insertions(+), 6 deletions(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 3b26f098094..7a22f2e6ec4 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -19,6 +19,7 @@ #include #include #include +#include #include "compat.h" #include "hash.h" #include "crc32c.h" @@ -1521,15 +1522,50 @@ out: return ret; } -int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root, - struct extent_buffer *orig_buf, struct extent_buffer *buf, - u32 *nr_extents) +/* when a block goes through cow, we update the reference counts of + * everything that block points to. The internal pointers of the block + * can be in just about any order, and it is likely to have clusters of + * things that are close together and clusters of things that are not. + * + * To help reduce the seeks that come with updating all of these reference + * counts, sort them by byte number before actual updates are done. + * + * struct refsort is used to match byte number to slot in the btree block. + * we sort based on the byte number and then use the slot to actually + * find the item. + */ +struct refsort { + u64 bytenr; + u32 slot; +}; + +/* + * for passing into sort() + */ +static int refsort_cmp(const void *a_void, const void *b_void) +{ + const struct refsort *a = a_void; + const struct refsort *b = b_void; + + if (a->bytenr < b->bytenr) + return -1; + if (a->bytenr > b->bytenr) + return 1; + return 0; +} + + +noinline int btrfs_inc_ref(struct btrfs_trans_handle *trans, + struct btrfs_root *root, + struct extent_buffer *orig_buf, + struct extent_buffer *buf, u32 *nr_extents) { u64 bytenr; u64 ref_root; u64 orig_root; u64 ref_generation; u64 orig_generation; + struct refsort *sorted; u32 nritems; u32 nr_file_extents = 0; struct btrfs_key key; @@ -1538,6 +1574,8 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root, int level; int ret = 0; int faili = 0; + int refi = 0; + int slot; int (*process_func)(struct btrfs_trans_handle *, struct btrfs_root *, u64, u64, u64, u64, u64, u64, u64, u64); @@ -1549,6 +1587,9 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root, nritems = btrfs_header_nritems(buf); level = btrfs_header_level(buf); + sorted = kmalloc(sizeof(struct refsort) * nritems, GFP_NOFS); + BUG_ON(!sorted); + if (root->ref_cows) { process_func = __btrfs_inc_extent_ref; } else { @@ -1561,6 +1602,11 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root, process_func = __btrfs_update_extent_ref; } + /* + * we make two passes through the items. In the first pass we + * only record the byte number and slot. Then we sort based on + * byte number and do the actual work based on the sorted results + */ for (i = 0; i < nritems; i++) { cond_resched(); if (level == 0) { @@ -1577,6 +1623,32 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root, continue; nr_file_extents++; + sorted[refi].bytenr = bytenr; + sorted[refi].slot = i; + refi++; + } else { + bytenr = btrfs_node_blockptr(buf, i); + sorted[refi].bytenr = bytenr; + sorted[refi].slot = i; + refi++; + } + } + /* + * if refi == 0, we didn't actually put anything into the sorted + * array and we're done + */ + if (refi == 0) + goto out; + + sort(sorted, refi, sizeof(struct refsort), refsort_cmp, NULL); + + for (i = 0; i < refi; i++) { + cond_resched(); + slot = sorted[i].slot; + bytenr = sorted[i].bytenr; + + if (level == 0) { + btrfs_item_key_to_cpu(buf, &key, slot); ret = process_func(trans, root, bytenr, orig_buf->start, buf->start, @@ -1585,25 +1657,25 @@ int btrfs_inc_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root, key.objectid); if (ret) { - faili = i; + faili = slot; WARN_ON(1); goto fail; } } else { - bytenr = btrfs_node_blockptr(buf, i); ret = process_func(trans, root, bytenr, orig_buf->start, buf->start, orig_root, ref_root, orig_generation, ref_generation, level - 1); if (ret) { - faili = i; + faili = slot; WARN_ON(1); goto fail; } } } out: + kfree(sorted); if (nr_extents) { if (level == 0) *nr_extents = nr_file_extents; @@ -1612,6 +1684,7 @@ out: } return 0; fail: + kfree(sorted); WARN_ON(1); return ret; } -- 2.41.1