Hello, On Sat, May 02, 2015 at 10:56:20PM +0800, Ming Lei wrote: > > Maybe just cap max_active to NR_OF_LOOP_DEVS * 16 or sth? But idk, > > It might not work because there are nested loop devices like fedora live CD, > and > in theory the max_active should have been set as loop's queue depth * > nr_loop, otherwise there may be possibility of hanging. > > So this patch is introduced.
If loop devices can be stacked, regardless of what you do with nr_active, it may deadlock. There needs to be a rescuer per each nesting level (or just one per device). This means that the current code is broken. > > how many concurrent workers are we talking about and why are we > > capping per-queue concurrency from worker pool side instead of command > > tag side? > > I think there should be performance advantage to make queue depth a bit more > because it can help to make queue pipeline as full. Also queue depth often > means how many requests the hardware can queue, and it is a bit different > with per-queue concurrency. I'm not really following. Can you please elaborate? Thanks. -- tejun -- 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/
