On Mon, 2008-11-24 at 07:52 +0900, James Bottomley wrote: > On Sun, 2008-11-23 at 13:39 +0000, David Woodhouse wrote: > > > We don't attempt to put non-contiguous ranges into a single TRIM yet. > > > > We don't even merge contiguous ranges -- I still need to fix the > > elevators to stop writes crossing writes, > > I don't think we want to do that ... it's legal if the write isn't a > barrier and it will inhibit merging. That may be just fine for a SSD, > but it's not for spinning media since they get better performance out of > merged writes. No, I just mean writes _to the same sector_. At the moment, we happily let those cross each other in the queue. We do notice this situation and preserve the ordering if the two requests cover _precisely_ the same range, but _overlapping_ writes may happen in any order. We should fix that, and it's only for _that_ purpose that I'm saying we treat writes and discards as identical. And then we can drop the barrier flag on discards. And _then_ we can think about special cases which let us merge non-contiguous discards. -- David Woodhouse Open Source Technology Centre David.Woodhouse@xxxxxxxxx Intel Corporation -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
