[PATCH 07/11] Btrfs: use percpu counter for fs_info->delalloc_bytes

[Miao Xie <miaox@cn.fujitsu.com>]

fs_info->delalloc_bytes is accessed very frequently, so use percpu counter
instead of the u64 variant for it to reduce the lock contention.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
 fs/btrfs/ctree.h       |  7 ++++---
 fs/btrfs/disk-io.c     | 18 ++++++++++++++----
 fs/btrfs/extent-tree.c |  6 ++++--
 fs/btrfs/inode.c       |  6 ++++--
 4 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1dcbbfd..51515a3 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1383,6 +1383,7 @@ struct btrfs_fs_info {
 	 */
 	struct list_head ordered_extents;
 
+	spinlock_t delalloc_lock;
 	/*
 	 * all of the inodes that have delalloc bytes.  It is possible for
 	 * this list to be empty even when there is still dirty data=ordered
@@ -1443,7 +1444,10 @@ struct btrfs_fs_info {
 
 	/* used to keep from writing metadata until there is a nice batch */
 	struct percpu_counter dirty_metadata_bytes;
+	struct percpu_counter delalloc_bytes;
 	s32 dirty_metadata_batch;
+	s32 delalloc_batch;
+
 	struct list_head dirty_cowonly_roots;
 
 	struct btrfs_fs_devices *fs_devices;
@@ -1459,9 +1463,6 @@ struct btrfs_fs_info {
 
 	struct reloc_control *reloc_ctl;
 
-	spinlock_t delalloc_lock;
-	u64 delalloc_bytes;
-
 	/* data_alloc_cluster is only used in ssd mode */
 	struct btrfs_free_cluster data_alloc_cluster;
 
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index adf270e..750afd4 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2006,10 +2006,16 @@ int open_ctree(struct super_block *sb,
 	fs_info->dirty_metadata_batch = PAGE_CACHE_SIZE *
 					(1 + ilog2(nr_cpu_ids));
 
+	ret = percpu_counter_init(&fs_info->delalloc_bytes, 0);
+	if (ret) {
+		err = ret;
+		goto fail_dirty_metadata_bytes;
+	}
+
 	fs_info->btree_inode = new_inode(sb);
 	if (!fs_info->btree_inode) {
 		err = -ENOMEM;
-		goto fail_dirty_metadata_bytes;
+		goto fail_delalloc_bytes;
 	}
 
 	mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);
@@ -2264,6 +2270,7 @@ int open_ctree(struct super_block *sb,
 	sectorsize = btrfs_super_sectorsize(disk_super);
 	stripesize = btrfs_super_stripesize(disk_super);
 	fs_info->dirty_metadata_batch = leafsize * (1 + ilog2(nr_cpu_ids));
+	fs_info->delalloc_batch = sectorsize * 512 * (1 + ilog2(nr_cpu_ids));
 
 	/*
 	 * mixed block groups end up with duplicate but slightly offset
@@ -2726,6 +2733,8 @@ fail_iput:
 
 	invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
 	iput(fs_info->btree_inode);
+fail_delalloc_bytes:
+	percpu_counter_destroy(&fs_info->delalloc_bytes);
 fail_dirty_metadata_bytes:
 	percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
 fail_bdi:
@@ -3357,9 +3366,9 @@ int close_ctree(struct btrfs_root *root)
 
 	btrfs_free_qgroup_config(root->fs_info);
 
-	if (fs_info->delalloc_bytes) {
-		printk(KERN_INFO "btrfs: at unmount delalloc count %llu\n",
-		       (unsigned long long)fs_info->delalloc_bytes);
+	if (percpu_counter_sum(&fs_info->delalloc_bytes)) {
+		printk(KERN_INFO "btrfs: at unmount delalloc count %lld\n",
+		       percpu_counter_sum(&fs_info->delalloc_bytes));
 	}
 
 	free_extent_buffer(fs_info->extent_root->node);
@@ -3407,6 +3416,7 @@ int close_ctree(struct btrfs_root *root)
 	btrfs_mapping_tree_free(&fs_info->mapping_tree);
 
 	percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
+	percpu_counter_destroy(&fs_info->delalloc_bytes);
 	bdi_destroy(&fs_info->bdi);
 	cleanup_srcu_struct(&fs_info->subvol_srcu);
 
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index a302e3a..2ec978b1 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3755,7 +3755,8 @@ static void shrink_delalloc(struct btrfs_root *root, u64 to_reclaim, u64 orig,
 	space_info = block_rsv->space_info;
 
 	smp_mb();
-	delalloc_bytes = root->fs_info->delalloc_bytes;
+	delalloc_bytes = percpu_counter_sum_positive(
+						&root->fs_info->delalloc_bytes);
 	if (delalloc_bytes == 0) {
 		if (trans)
 			return;
@@ -3794,7 +3795,8 @@ static void shrink_delalloc(struct btrfs_root *root, u64 to_reclaim, u64 orig,
 				break;
 		}
 		smp_mb();
-		delalloc_bytes = root->fs_info->delalloc_bytes;
+		delalloc_bytes = percpu_counter_sum_positive(
+						&root->fs_info->delalloc_bytes);
 	}
 }
 
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index fb70bcb..c29299d 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1510,7 +1510,8 @@ static void btrfs_set_bit_hook(struct inode *inode,
 
 		spin_lock(&root->fs_info->delalloc_lock);
 		BTRFS_I(inode)->delalloc_bytes += len;
-		root->fs_info->delalloc_bytes += len;
+		__percpu_counter_add(&root->fs_info->delalloc_bytes, len,
+				     root->fs_info->delalloc_batch);
 		if (do_list && list_empty(&BTRFS_I(inode)->delalloc_inodes)) {
 			list_add_tail(&BTRFS_I(inode)->delalloc_inodes,
 				      &root->fs_info->delalloc_inodes);
@@ -1551,7 +1552,8 @@ static void btrfs_clear_bit_hook(struct inode *inode,
 			btrfs_free_reserved_data_space(inode, len);
 
 		spin_lock(&root->fs_info->delalloc_lock);
-		root->fs_info->delalloc_bytes -= len;
+		__percpu_counter_add(&root->fs_info->delalloc_bytes, -len,
+				     root->fs_info->delalloc_batch);
 		BTRFS_I(inode)->delalloc_bytes -= len;
 
 		if (do_list && BTRFS_I(inode)->delalloc_bytes == 0 &&
-- 
1.7.11.7