[PATCH] btrfs: use customized batch size for total_bytes_pinned

[Ethan Lien <ethanlien@synology.com>]

We use percpu_counter to reduce lock contention of frequently updated
counter. But the default 32 batch size is suitable only for inc/dec
update, not for sector size update. The end result is we still acquire
spin lock for every percpu_counter_add(). So use customized batch size
for total_bytes_pinned as we already done for dirty_metadata_bytes
and delalloc_bytes. Also we fix dirty_metadata_bytes to use
__percpu_counter_compare of customized batch so we get precise value of
dirty_metadata_bytes.

Signed-off-by: Ethan Lien <ethanlien@synology.com>
---
 fs/btrfs/ctree.h       |  1 +
 fs/btrfs/disk-io.c     | 10 ++++++----
 fs/btrfs/extent-tree.c | 43 +++++++++++++++++++++++++++---------------
 3 files changed, 35 insertions(+), 19 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 118346aceea9..df682a521635 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -422,6 +422,7 @@ struct btrfs_space_info {
 	 * time the transaction commits.
 	 */
 	struct percpu_counter total_bytes_pinned;
+	s32 total_bytes_pinned_batch;
 
 	struct list_head list;
 	/* Protected by the spinlock 'lock'. */
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 205092dc9390..dfed08e70ec1 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -961,8 +961,9 @@ static int btree_writepages(struct address_space *mapping,
 
 		fs_info = BTRFS_I(mapping->host)->root->fs_info;
 		/* this is a bit racy, but that's ok */
-		ret = percpu_counter_compare(&fs_info->dirty_metadata_bytes,
-					     BTRFS_DIRTY_METADATA_THRESH);
+		ret = __percpu_counter_compare(&fs_info->dirty_metadata_bytes,
+					     BTRFS_DIRTY_METADATA_THRESH,
+					     fs_info->dirty_metadata_batch);
 		if (ret < 0)
 			return 0;
 	}
@@ -4150,8 +4151,9 @@ static void __btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info,
 	if (flush_delayed)
 		btrfs_balance_delayed_items(fs_info);
 
-	ret = percpu_counter_compare(&fs_info->dirty_metadata_bytes,
-				     BTRFS_DIRTY_METADATA_THRESH);
+	ret = __percpu_counter_compare(&fs_info->dirty_metadata_bytes,
+				     BTRFS_DIRTY_METADATA_THRESH,
+				     fs_info->dirty_metadata_batch);
 	if (ret > 0) {
 		balance_dirty_pages_ratelimited(fs_info->btree_inode->i_mapping);
 	}
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 3d9fe58c0080..a067c047904c 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -758,7 +758,8 @@ static void add_pinned_bytes(struct btrfs_fs_info *fs_info, s64 num_bytes,
 
 	space_info = __find_space_info(fs_info, flags);
 	ASSERT(space_info);
-	percpu_counter_add(&space_info->total_bytes_pinned, num_bytes);
+	percpu_counter_add_batch(&space_info->total_bytes_pinned, num_bytes,
+		    space_info->total_bytes_pinned_batch);
 }
 
 /*
@@ -2598,8 +2599,9 @@ static int cleanup_ref_head(struct btrfs_trans_handle *trans,
 			flags = BTRFS_BLOCK_GROUP_METADATA;
 		space_info = __find_space_info(fs_info, flags);
 		ASSERT(space_info);
-		percpu_counter_add(&space_info->total_bytes_pinned,
-				   -head->num_bytes);
+		percpu_counter_add_batch(&space_info->total_bytes_pinned,
+				   -head->num_bytes,
+				   space_info->total_bytes_pinned_batch);
 
 		if (head->is_data) {
 			spin_lock(&delayed_refs->lock);
@@ -4035,6 +4037,10 @@ static int create_space_info(struct btrfs_fs_info *info, u64 flags)
 	INIT_LIST_HEAD(&space_info->ro_bgs);
 	INIT_LIST_HEAD(&space_info->tickets);
 	INIT_LIST_HEAD(&space_info->priority_tickets);
+	if (flags & BTRFS_BLOCK_GROUP_DATA)
+		space_info->total_bytes_pinned_batch = info->delalloc_batch;
+	else
+		space_info->total_bytes_pinned_batch = info->dirty_metadata_batch;
 
 	ret = kobject_init_and_add(&space_info->kobj, &space_info_ktype,
 				    info->space_info_kobj, "%s",
@@ -4309,9 +4315,10 @@ int btrfs_alloc_data_chunk_ondemand(struct btrfs_inode *inode, u64 bytes)
 		 * allocation, and no removed chunk in current transaction,
 		 * don't bother committing the transaction.
 		 */
-		have_pinned_space = percpu_counter_compare(
+		have_pinned_space = __percpu_counter_compare(
 			&data_sinfo->total_bytes_pinned,
-			used + bytes - data_sinfo->total_bytes);
+			used + bytes - data_sinfo->total_bytes,
+			data_sinfo->total_bytes_pinned_batch);
 		spin_unlock(&data_sinfo->lock);
 
 		/* commit the current transaction and try again */
@@ -4912,8 +4919,9 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
 		return 0;
 
 	/* See if there is enough pinned space to make this reservation */
-	if (percpu_counter_compare(&space_info->total_bytes_pinned,
-				   bytes) >= 0)
+	if (__percpu_counter_compare(&space_info->total_bytes_pinned,
+				   bytes,
+				   space_info->total_bytes_pinned_batch) >= 0)
 		goto commit;
 
 	/*
@@ -4930,8 +4938,9 @@ static int may_commit_transaction(struct btrfs_fs_info *fs_info,
 		bytes -= delayed_rsv->size;
 	spin_unlock(&delayed_rsv->lock);
 
-	if (percpu_counter_compare(&space_info->total_bytes_pinned,
-				   bytes) < 0) {
+	if (__percpu_counter_compare(&space_info->total_bytes_pinned,
+				   bytes,
+				   space_info->total_bytes_pinned_batch) < 0) {
 		return -ENOSPC;
 	}
 
@@ -6268,8 +6277,9 @@ static int update_block_group(struct btrfs_trans_handle *trans,
 			trace_btrfs_space_reservation(info, "pinned",
 						      cache->space_info->flags,
 						      num_bytes, 1);
-			percpu_counter_add(&cache->space_info->total_bytes_pinned,
-					   num_bytes);
+			percpu_counter_add_batch(&cache->space_info->total_bytes_pinned,
+					   num_bytes,
+					   cache->space_info->total_bytes_pinned_batch);
 			set_extent_dirty(info->pinned_extents,
 					 bytenr, bytenr + num_bytes - 1,
 					 GFP_NOFS | __GFP_NOFAIL);
@@ -6347,7 +6357,8 @@ static int pin_down_extent(struct btrfs_fs_info *fs_info,
 
 	trace_btrfs_space_reservation(fs_info, "pinned",
 				      cache->space_info->flags, num_bytes, 1);
-	percpu_counter_add(&cache->space_info->total_bytes_pinned, num_bytes);
+	percpu_counter_add_batch(&cache->space_info->total_bytes_pinned,
+		    num_bytes, cache->space_info->total_bytes_pinned_batch);
 	set_extent_dirty(fs_info->pinned_extents, bytenr,
 			 bytenr + num_bytes - 1, GFP_NOFS | __GFP_NOFAIL);
 	return 0;
@@ -6711,7 +6722,8 @@ static int unpin_extent_range(struct btrfs_fs_info *fs_info,
 		trace_btrfs_space_reservation(fs_info, "pinned",
 					      space_info->flags, len, 0);
 		space_info->max_extent_size = 0;
-		percpu_counter_add(&space_info->total_bytes_pinned, -len);
+		percpu_counter_add_batch(&space_info->total_bytes_pinned,
+			    -len, space_info->total_bytes_pinned_batch);
 		if (cache->ro) {
 			space_info->bytes_readonly += len;
 			readonly = true;
@@ -10764,8 +10776,9 @@ void btrfs_delete_unused_bgs(struct btrfs_fs_info *fs_info)
 
 		space_info->bytes_pinned -= block_group->pinned;
 		space_info->bytes_readonly += block_group->pinned;
-		percpu_counter_add(&space_info->total_bytes_pinned,
-				   -block_group->pinned);
+		percpu_counter_add_batch(&space_info->total_bytes_pinned,
+				   -block_group->pinned,
+				   space_info->total_bytes_pinned_batch);
 		block_group->pinned = 0;
 
 		spin_unlock(&block_group->lock);
-- 
2.17.1