On 10/04/2018 03:16 AM, Jan Kara wrote: > On Wed 12-09-18 15:28:52, Waiman Long wrote: >> From: Davidlohr Bueso <dave@xxxxxxxxxxxx> >> >> Instead of the current O(N) implementation, at the cost >> of adding an atomic counter, we can convert the call to >> an atomic_read(). The counter only serves for accounting >> empty to non-empty transitions, and vice versa; therefore >> only modified twice for each of the lists during the >> lifetime of the dlock (while used). >> >> In addition, to be able to unaccount a list_del(), we >> add a dlist pointer to each head, thus minimizing the >> overall memory footprint. >> >> Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx> >> Acked-by: Waiman Long <longman@xxxxxxxxxx> > So I was wondering: Is this really worth it? AFAICS we have a single call > site for dlock_lists_empty() and that happens during umount where we don't > really care about this optimization. So it seems like unnecessary > complication to me at this point? If someone comes up with a usecase that > needs fast dlock_lists_empty(), then sure, we can do this... > Yes, that is true. We can skip this patch for the time being until a use case comes up which requires dlock_lists_empty() to be used in the fast path. Cheers, Longman
