Miao Xie
2013-Jan-10 12:48 UTC
[PATCH 06/11] Btrfs: use percpu counter for dirty metadata count
->dirty_metadata_bytes is accessed very frequently, so use percpu counter
instead of the u64 variant to reduce the contention of the lock.
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
fs/btrfs/ctree.h | 9 ++++----
fs/btrfs/disk-io.c | 64 ++++++++++++++++++++++++++++------------------------
fs/btrfs/extent_io.c | 9 +++-----
3 files changed, 42 insertions(+), 40 deletions(-)
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 201be7d..1dcbbfd 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -191,6 +191,8 @@ static int btrfs_csum_sizes[] = { 4, 0 };
/* ioprio of readahead is set to idle */
#define BTRFS_IOPRIO_READA (IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0))
+#define BTRFS_DIRTY_METADATA_THRESH (32 * 1024 * 1024)
+
/*
* The key defines the order in the tree, and so it also defines (optimal)
* block layout.
@@ -1439,10 +1441,9 @@ struct btrfs_fs_info {
u64 total_pinned;
- /* protected by the delalloc lock, used to keep from writing
- * metadata until there is a nice batch
- */
- u64 dirty_metadata_bytes;
+ /* used to keep from writing metadata until there is a nice batch */
+ struct percpu_counter dirty_metadata_bytes;
+ s32 dirty_metadata_batch;
struct list_head dirty_cowonly_roots;
struct btrfs_fs_devices *fs_devices;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 9263c6e..adf270e 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -946,18 +946,20 @@ static int btree_writepages(struct address_space *mapping,
struct writeback_control *wbc)
{
struct extent_io_tree *tree;
+ struct btrfs_fs_info *fs_info;
+ int ret;
+
tree = &BTRFS_I(mapping->host)->io_tree;
if (wbc->sync_mode == WB_SYNC_NONE) {
- struct btrfs_root *root = BTRFS_I(mapping->host)->root;
- u64 num_dirty;
- unsigned long thresh = 32 * 1024 * 1024;
if (wbc->for_kupdate)
return 0;
+ fs_info = BTRFS_I(mapping->host)->root->fs_info;
/* this is a bit racy, but that''s ok */
- num_dirty = root->fs_info->dirty_metadata_bytes;
- if (num_dirty < thresh)
+ ret = percpu_counter_compare(&fs_info->dirty_metadata_bytes,
+ BTRFS_DIRTY_METADATA_THRESH);
+ if (ret < 0)
return 0;
}
return btree_write_cache_pages(mapping, wbc);
@@ -1125,24 +1127,16 @@ struct extent_buffer *read_tree_block(struct btrfs_root
*root, u64 bytenr,
void clean_tree_block(struct btrfs_trans_handle *trans, struct btrfs_root
*root,
struct extent_buffer *buf)
{
+ struct btrfs_fs_info *fs_info = root->fs_info;
+
if (btrfs_header_generation(buf) =-
root->fs_info->running_transaction->transid) {
+ fs_info->running_transaction->transid) {
btrfs_assert_tree_locked(buf);
if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &buf->bflags)) {
- spin_lock(&root->fs_info->delalloc_lock);
- if (root->fs_info->dirty_metadata_bytes >= buf->len)
- root->fs_info->dirty_metadata_bytes -= buf->len;
- else {
- spin_unlock(&root->fs_info->delalloc_lock);
- btrfs_panic(root->fs_info, -EOVERFLOW,
- "Can''t clear %lu bytes from "
- " dirty_mdatadata_bytes (%llu)",
- buf->len,
- root->fs_info->dirty_metadata_bytes);
- }
- spin_unlock(&root->fs_info->delalloc_lock);
-
+ __percpu_counter_add(&fs_info->dirty_metadata_bytes,
+ -buf->len,
+ fs_info->dirty_metadata_batch);
/* ugh, clear_extent_buffer_dirty needs to lock the page */
btrfs_set_lock_blocking(buf);
clear_extent_buffer_dirty(buf);
@@ -2004,10 +1998,18 @@ int open_ctree(struct super_block *sb,
goto fail_srcu;
}
+ ret = percpu_counter_init(&fs_info->dirty_metadata_bytes, 0);
+ if (ret) {
+ err = ret;
+ goto fail_bdi;
+ }
+ fs_info->dirty_metadata_batch = PAGE_CACHE_SIZE *
+ (1 + ilog2(nr_cpu_ids));
+
fs_info->btree_inode = new_inode(sb);
if (!fs_info->btree_inode) {
err = -ENOMEM;
- goto fail_bdi;
+ goto fail_dirty_metadata_bytes;
}
mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);
@@ -2261,6 +2263,7 @@ int open_ctree(struct super_block *sb,
leafsize = btrfs_super_leafsize(disk_super);
sectorsize = btrfs_super_sectorsize(disk_super);
stripesize = btrfs_super_stripesize(disk_super);
+ fs_info->dirty_metadata_batch = leafsize * (1 + ilog2(nr_cpu_ids));
/*
* mixed block groups end up with duplicate but slightly offset
@@ -2723,6 +2726,8 @@ fail_iput:
invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
iput(fs_info->btree_inode);
+fail_dirty_metadata_bytes:
+ percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
fail_bdi:
bdi_destroy(&fs_info->bdi);
fail_srcu:
@@ -3401,6 +3406,7 @@ int close_ctree(struct btrfs_root *root)
btrfs_close_devices(fs_info->fs_devices);
btrfs_mapping_tree_free(&fs_info->mapping_tree);
+ percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
bdi_destroy(&fs_info->bdi);
cleanup_srcu_struct(&fs_info->subvol_srcu);
@@ -3443,11 +3449,10 @@ void btrfs_mark_buffer_dirty(struct extent_buffer *buf)
(unsigned long long)transid,
(u64)atomic64_read(&root->fs_info->generation));
was_dirty = set_extent_buffer_dirty(buf);
- if (!was_dirty) {
- spin_lock(&root->fs_info->delalloc_lock);
- root->fs_info->dirty_metadata_bytes += buf->len;
- spin_unlock(&root->fs_info->delalloc_lock);
- }
+ if (!was_dirty)
+ __percpu_counter_add(&root->fs_info->dirty_metadata_bytes,
+ buf->len,
+ root->fs_info->dirty_metadata_batch);
}
static void __btrfs_btree_balance_dirty(struct btrfs_root *root,
@@ -3457,8 +3462,7 @@ static void __btrfs_btree_balance_dirty(struct btrfs_root
*root,
* looks as though older kernels can get into trouble with
* this code, they end up stuck in balance_dirty_pages forever
*/
- u64 num_dirty;
- unsigned long thresh = 32 * 1024 * 1024;
+ int ret;
if (current->flags & PF_MEMALLOC)
return;
@@ -3466,9 +3470,9 @@ static void __btrfs_btree_balance_dirty(struct btrfs_root
*root,
if (flush_delayed)
btrfs_balance_delayed_items(root);
- num_dirty = root->fs_info->dirty_metadata_bytes;
-
- if (num_dirty > thresh) {
+ ret = percpu_counter_compare(&root->fs_info->dirty_metadata_bytes,
+ BTRFS_DIRTY_METADATA_THRESH);
+ if (ret > 0) {
balance_dirty_pages_ratelimited_nr(
root->fs_info->btree_inode->i_mapping, 1);
}
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 1b319df..2d4bdfd 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3124,12 +3124,9 @@ static int lock_extent_buffer_for_io(struct extent_buffer
*eb,
set_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags);
spin_unlock(&eb->refs_lock);
btrfs_set_header_flag(eb, BTRFS_HEADER_FLAG_WRITTEN);
- spin_lock(&fs_info->delalloc_lock);
- if (fs_info->dirty_metadata_bytes >= eb->len)
- fs_info->dirty_metadata_bytes -= eb->len;
- else
- WARN_ON(1);
- spin_unlock(&fs_info->delalloc_lock);
+ __percpu_counter_add(&fs_info->dirty_metadata_bytes,
+ -eb->len,
+ fs_info->dirty_metadata_batch);
ret = 1;
} else {
spin_unlock(&eb->refs_lock);
--
1.7.11.7
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