[0/2] xfs: Use wake_q for waking up log space waiters

Message

Waiman Long Aug. 23, 2018, 4:26 p.m. UTC

While running the AIM7 microbenchmark, it was found that there was
a severe spinlock contention problem in the current XFS log space
reservation code. To alleviate the problem, the log space waiter
waiting and waking functions are modified to use the wake_q for waking
up waiters without holding the lock so as to reduce the lock hold time.

The result was a 4X performance improvement in that microbenchmark
which is worth persuing.

Patch 1 is an enablement patch to make wake_q service available to
kernel modules.

Patch 2 changes the XFS log space reservation code to use wake_q for
task wakeup.

Waiman Long (2):
  sched/core: Export wake_q functions to kernel modules
  xfs: Use wake_q for waking up log space waiters

 fs/xfs/xfs_log.c             | 48 ++++++++++++++++++++++++++++++++++----------
 include/linux/sched/wake_q.h |  5 +++++
 kernel/sched/core.c          |  2 ++
 3 files changed, 44 insertions(+), 11 deletions(-)