On Mon, May 11 2009, Theodore Tso wrote: > On Mon, May 11, 2009 at 10:12:16AM +0200, Jens Axboe wrote: > > > > I largely agree with this. I think that trims should be queued and > > postponed until the drive is largely idle. I don't want to put this IO > > tracking in the block layer though, it's going to slow down our iops > > rates for writes. Providing the functionality in the block layer does > > make sense though, since it sits between that and the fs anyway. So just > > not part of the generic IO path, but a set of helpers on the side. > > Yes, I agree. However, in that case, we need two things from the > block I/O path. (A) The discard management layer needs a way of > knowing that the block device has become idle, and (B) ideally there We don't have to inform of such a condition, the block layer can check for existing pending trims and kick those off at an appropriate time. > should be a more efficient method for sending trim requests to the I/O > submission path. If we batch the results, when we *do* send the > discard requests, we may be sending several hundred discards, and it > would be useful if we could pass into the I/O submission path a linked > list of regions, so the queue can be drained *once*, and then a whole > series of discards can be sent to the device all at once. > > Does that make sense to you? Agree, we definitely only want to do the queue quiesce once for passing down a series of trims. With the delayed trim queuing, that isn't very difficult. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
