tree d9f678310c6c8a4daf2003fa4f6b4164111dbbd7
parent 3f157a2fd2ad731e1ed9964fecdc5f459f04a4a4
author Chris Mason <chris.mason@oracle.com> 1214424844 -0400
committer Chris Mason <chris.mason@oracle.com> 1222355044 -0400

Btrfs: Reduce contention on the root node

This calls unlock_up sooner in btrfs_search_slot in order to decrease the
amount of work done with the higher level tree locks held.

Also, it changes btrfs_tree_lock to spin for a big against the page lock
before scheduling.  This makes a big difference in context switch rate under
highly contended workloads.

Longer term, a better locking structure is needed than the page lock.

Signed-off-by: Chris Mason <chris.mason@oracle.com>