[v2] btrfs: track odirect bytes in flight
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Message ID 20190425205247.99177-1-josef@toxicpanda.com
State New
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  • [v2] btrfs: track odirect bytes in flight
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Commit Message

Josef Bacik April 25, 2019, 8:52 p.m. UTC
When diagnosing a slowdown of generic/224 I noticed we were not doing
anything when calling into shrink_delalloc().  This is because all
writes in 224 are O_DIRECT, not delalloc, and thus our delalloc_bytes
counter is 0, which short circuits most of the work inside of
shrink_delalloc().  However O_DIRECT writes still consume metadata
resources and generate ordered extents, which we can still wait on.

Fix this by tracking outstandingn odirect write bytes, and use this as
well as the delalloc byts counter to decide if we need to lookup and
wait on any ordered extents.  If we have more odirect writes than
delalloc bytes we'll go ahead and wait on any ordered extents
irregardless of our flush state as flushing delalloc is likely to not
gain us anything.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
v1->v2:
- updated the changelog

 fs/btrfs/ctree.h        |  1 +
 fs/btrfs/disk-io.c      | 15 ++++++++++++++-
 fs/btrfs/extent-tree.c  | 17 +++++++++++++++--
 fs/btrfs/ordered-data.c |  9 ++++++++-
 4 files changed, 38 insertions(+), 4 deletions(-)

Comments

David Sterba April 29, 2019, 6:17 p.m. UTC | #1
On Thu, Apr 25, 2019 at 04:52:47PM -0400, Josef Bacik wrote:
> When diagnosing a slowdown of generic/224 I noticed we were not doing
> anything when calling into shrink_delalloc().  This is because all
> writes in 224 are O_DIRECT, not delalloc, and thus our delalloc_bytes
> counter is 0, which short circuits most of the work inside of
> shrink_delalloc().  However O_DIRECT writes still consume metadata
> resources and generate ordered extents, which we can still wait on.
> 
> Fix this by tracking outstandingn odirect write bytes, and use this as
> well as the delalloc byts counter to decide if we need to lookup and
> wait on any ordered extents.  If we have more odirect writes than
> delalloc bytes we'll go ahead and wait on any ordered extents
> irregardless of our flush state as flushing delalloc is likely to not
> gain us anything.

Ok, that helps.

> Signed-off-by: Josef Bacik <josef@toxicpanda.com>
> ---
> v1->v2:
> - updated the changelog
> 
>  fs/btrfs/ctree.h        |  1 +
>  fs/btrfs/disk-io.c      | 15 ++++++++++++++-
>  fs/btrfs/extent-tree.c  | 17 +++++++++++++++--
>  fs/btrfs/ordered-data.c |  9 ++++++++-
>  4 files changed, 38 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index 7e774d48c48c..e293d74b2ead 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -1016,6 +1016,7 @@ 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;
> +	struct percpu_counter odirect_bytes;

I've changed odirect to dio everywhere, as this is the common reference
to direct IO kernel code, O_DIRECT is for userspace.

Patch
diff mbox series

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 7e774d48c48c..e293d74b2ead 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1016,6 +1016,7 @@  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;
+	struct percpu_counter odirect_bytes;
 	s32 dirty_metadata_batch;
 	s32 delalloc_batch;
 
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 7a88de4be8d7..3f0b1854cedc 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2641,11 +2641,17 @@  int open_ctree(struct super_block *sb,
 		goto fail;
 	}
 
-	ret = percpu_counter_init(&fs_info->dirty_metadata_bytes, 0, GFP_KERNEL);
+	ret = percpu_counter_init(&fs_info->odirect_bytes, 0, GFP_KERNEL);
 	if (ret) {
 		err = ret;
 		goto fail_srcu;
 	}
+
+	ret = percpu_counter_init(&fs_info->dirty_metadata_bytes, 0, GFP_KERNEL);
+	if (ret) {
+		err = ret;
+		goto fail_odirect_bytes;
+	}
 	fs_info->dirty_metadata_batch = PAGE_SIZE *
 					(1 + ilog2(nr_cpu_ids));
 
@@ -3344,6 +3350,8 @@  int open_ctree(struct super_block *sb,
 	percpu_counter_destroy(&fs_info->delalloc_bytes);
 fail_dirty_metadata_bytes:
 	percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
+fail_odirect_bytes:
+	percpu_counter_destroy(&fs_info->odirect_bytes);
 fail_srcu:
 	cleanup_srcu_struct(&fs_info->subvol_srcu);
 fail:
@@ -4025,6 +4033,10 @@  void close_ctree(struct btrfs_fs_info *fs_info)
 		       percpu_counter_sum(&fs_info->delalloc_bytes));
 	}
 
+	if (percpu_counter_sum(&fs_info->odirect_bytes))
+		btrfs_info(fs_info, "at unmount odirect count %lld",
+			   percpu_counter_sum(&fs_info->odirect_bytes));
+
 	btrfs_sysfs_remove_mounted(fs_info);
 	btrfs_sysfs_remove_fsid(fs_info->fs_devices);
 
@@ -4056,6 +4068,7 @@  void close_ctree(struct btrfs_fs_info *fs_info)
 
 	percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
 	percpu_counter_destroy(&fs_info->delalloc_bytes);
+	percpu_counter_destroy(&fs_info->odirect_bytes);
 	percpu_counter_destroy(&fs_info->dev_replace.bio_counter);
 	cleanup_srcu_struct(&fs_info->subvol_srcu);
 
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index d0626f945de2..0982456ebabb 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4727,6 +4727,7 @@  static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim,
 	struct btrfs_space_info *space_info;
 	struct btrfs_trans_handle *trans;
 	u64 delalloc_bytes;
+	u64 odirect_bytes;
 	u64 async_pages;
 	u64 items;
 	long time_left;
@@ -4742,7 +4743,9 @@  static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim,
 
 	delalloc_bytes = percpu_counter_sum_positive(
 						&fs_info->delalloc_bytes);
-	if (delalloc_bytes == 0) {
+	odirect_bytes = percpu_counter_sum_positive(
+						&fs_info->odirect_bytes);
+	if (delalloc_bytes == 0 && odirect_bytes == 0) {
 		if (trans)
 			return;
 		if (wait_ordered)
@@ -4750,8 +4753,16 @@  static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim,
 		return;
 	}
 
+	/*
+	 * If we are doing more ordered than delalloc we need to just wait on
+	 * ordered extents, otherwise we'll waste time trying to flush delalloc
+	 * that likely won't give us the space back we need.
+	 */
+	if (odirect_bytes > delalloc_bytes)
+		wait_ordered = true;
+
 	loops = 0;
-	while (delalloc_bytes && loops < 3) {
+	while ((delalloc_bytes || odirect_bytes)  && loops < 3) {
 		nr_pages = min(delalloc_bytes, to_reclaim) >> PAGE_SHIFT;
 
 		/*
@@ -4801,6 +4812,8 @@  static void shrink_delalloc(struct btrfs_fs_info *fs_info, u64 to_reclaim,
 		}
 		delalloc_bytes = percpu_counter_sum_positive(
 						&fs_info->delalloc_bytes);
+		odirect_bytes = percpu_counter_sum_positive(
+						&fs_info->odirect_bytes);
 	}
 }
 
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 6fde2b2741ef..967c62b85d77 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -194,8 +194,11 @@  static int __btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
 	if (type != BTRFS_ORDERED_IO_DONE && type != BTRFS_ORDERED_COMPLETE)
 		set_bit(type, &entry->flags);
 
-	if (dio)
+	if (dio) {
+		percpu_counter_add_batch(&fs_info->odirect_bytes, len,
+					 fs_info->delalloc_batch);
 		set_bit(BTRFS_ORDERED_DIRECT, &entry->flags);
+	}
 
 	/* one ref for the tree */
 	refcount_set(&entry->refs, 1);
@@ -468,6 +471,10 @@  void btrfs_remove_ordered_extent(struct inode *inode,
 	if (root != fs_info->tree_root)
 		btrfs_delalloc_release_metadata(btrfs_inode, entry->len, false);
 
+	if (test_bit(BTRFS_ORDERED_DIRECT, &entry->flags))
+		percpu_counter_add_batch(&fs_info->odirect_bytes, -entry->len,
+					 fs_info->delalloc_batch);
+
 	tree = &btrfs_inode->ordered_tree;
 	spin_lock_irq(&tree->lock);
 	node = &entry->rb_node;