On Thu, 2015-04-30 at 17:12 -0400, Waiman Long wrote: > In up_write()/up_read(), rwsem_wake() will be called whenever it > detects that some writers/readers are waiting. The rwsem_wake() > function will take the wait_lock and call __rwsem_do_wake() to do the > real wakeup. For a heavily contended rwsem, doing a spin_lock() on > wait_lock will cause further contention on the heavily contended rwsem > cacheline resulting in delay in the completion of the up_read/up_write > operations. > > This patch makes the wait_lock taking and the call to __rwsem_do_wake() > optional if at least one spinning writer is present. The spinning > writer will be able to take the rwsem and call rwsem_wake() later > when it calls up_write(). With the presence of a spinning writer, > rwsem_wake() will now try to acquire the lock using trylock. If that > fails, it will just quit. > > Signed-off-by: Waiman Long <waiman.l...@hp.com> > Suggested-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Reviewed-by: Davidlohr Bueso <d...@stgolabs.net> -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
