Description of problem:
Currently 'features.locks-notify-contention' is disabled by default. This option, when enabled, instructs the locks xlator to send an upcall notification to the current owner of a lock whenever another client tries to acquire a conflicting lock.
Both AFR and EC support this notification and react by releasing the lock as soon as possible. This is extremely useful when eager-lock is enabled (it is by default) because it allows AFR and EC to use it to improve performance but we don't loose performance on other clients when access to the same resource is required.
Since eager-lock is enabled by default, it doesn't make sense to keep contention notification disabled.
Version-Release number of selected component (if applicable): mainline
Steps to Reproduce:
REVIEW: https://review.gluster.org/22828 (locks: enable notify-contention by default) posted (#1) for review on master by Xavi Hernandez
REVIEW: https://review.gluster.org/22828 (locks: enable notify-contention by default) merged (#4) on master by Pranith Kumar Karampuri