md/raid10: prevent unnecessary calls to wake_up() in fast path

Currently, wake_up() is called unconditionally in fast path such as
raid10_make_request(), which will cause lock contention under high
concurrency:

raid10_make_request
 wake_up
  __wake_up_common_lock
   spin_lock_irqsave

Improve performance by only call wake_up() if waitqueue is not empty
in allow_barrier() and raid10_make_request().

Signed-off-by: Yu Kuai <[email protected]>
Reviewed-by: Logan Gunthorpe <[email protected]>
Acked-by: Guoqing Jiang <[email protected]>
Signed-off-by: Song Liu <[email protected]>

0 files changed, 0 insertions, 0 deletions