On Sat, 15 Oct 2016 03:42:42 -0700 Joel Fernandes <joelaf@xxxxxxxxxx> wrote: > The purge_lock spinlock causes high latencies with non RT kernel. This has been > reported multiple times on lkml [1] [2] and affects applications like audio. > > In this patch, I replace the spinlock with an atomic refcount so that > preemption is kept turned on during purge. This Ok to do since [3] builds the > lazy free list in advance and atomically retrieves the list so any instance of > purge will have its own list it is purging. Since the individual vmap area > frees are themselves protected by a lock, this is Ok. This is a good idea, and good results, but that's not what the spinlock was for -- it was for enforcing the sync semantics. Going this route, you'll have to audit callers to expect changed behavior and change documentation of sync parameter. I suspect a better approach would be to instead use a mutex for this, and require that all sync=1 callers be able to sleep. I would say that most probably already can. Thanks, Nick -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>