Btrfs devel - Mar 2013 - [PATCH] Btrfs: get better concurrency for snapshot-aware defrag work

Using spinning case instead of blocking will result in better concurrency
overall.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
---
 fs/btrfs/inode.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 13ab4de..1f268888 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2312,6 +2312,7 @@ again:
 	key.type = BTRFS_EXTENT_DATA_KEY;
 	key.offset = start;
 
+	path->leave_spinning = 1;
 	if (merge) {
 		struct btrfs_file_extent_item *fi;
 		u64 extent_len;
@@ -2368,6 +2369,7 @@ again:
 
 	btrfs_mark_buffer_dirty(leaf);
 	inode_add_bytes(inode, len);
+	btrfs_release_path(path);
 
 	ret = btrfs_inc_extent_ref(trans, root, new->bytenr,
 			new->disk_len, 0,
@@ -2381,6 +2383,7 @@ again:
 	ret = 1;
 out_free_path:
 	btrfs_release_path(path);
+	path->leave_spinning = 0;
 	btrfs_end_transaction(trans, root);
 out_unlock:
 	unlock_extent_cached(&BTRFS_I(inode)->io_tree, lock_start, lock_end,
-- 
1.7.7.6

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On Mon, Mar 11, 2013 at 05:20:58PM +0800, Liu Bo wrote:
> Using spinning case instead of blocking will result in better concurrency
> overall.
Do you have numbers to support that?

david
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On Mon, Mar 11, 2013 at 06:26:40PM +0100, David Sterba
wrote:
> On Mon, Mar 11, 2013 at 05:20:58PM +0800, Liu Bo wrote:
> > Using spinning case instead of blocking will result in better
concurrency
> > overall.
> 
> Do you have numbers to support that?
> 
Sorry, I don''t, just judging from what leave_spinning is desiged for
and the
similar usecases, like insert_reserved_file_extents(), which is also involved in
endio write worker.

thanks,
liubo
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On Mon, Mar 11, 2013 at 07:44:04PM -0600, Liu Bo wrote:
> On Mon, Mar 11, 2013 at 06:26:40PM +0100, David Sterba wrote:
> > On Mon, Mar 11, 2013 at 05:20:58PM +0800, Liu Bo wrote:
> > > Using spinning case instead of blocking will result in better
concurrency
> > > overall.
> > 
> > Do you have numbers to support that?
> > 
> 
> Sorry, I don''t, just judging from what leave_spinning is desiged
for and the
> similar usecases, like insert_reserved_file_extents(), which is also
involved in
> endio write worker.
Leaving the path spinning is always faster.  As long as you''re sure the
code inside doesn''t schedule it is the right choice.

-chris

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On Thu, Mar 14, 2013 at 02:38:29PM -0400, Chris Mason
wrote:
> On Mon, Mar 11, 2013 at 07:44:04PM -0600, Liu Bo wrote:
> > On Mon, Mar 11, 2013 at 06:26:40PM +0100, David Sterba wrote:
> > > On Mon, Mar 11, 2013 at 05:20:58PM +0800, Liu Bo wrote:
> > > > Using spinning case instead of blocking will result in
better concurrency
> > > > overall.
> > > 
> > > Do you have numbers to support that?
> > > 
> > 
> > Sorry, I don''t, just judging from what leave_spinning is
desiged for and the
> > similar usecases, like insert_reserved_file_extents(), which is also
involved in
> > endio write worker.
> 
> Leaving the path spinning is always faster.  As long as you''re
sure the
> code inside doesn''t schedule it is the right choice.
> 
Yeah, I''ve taken care of schedule thing :)

thanks,
liubo
> 
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