On Thu, 2010-11-18 at 09:29 -0500, Christoph Hellwig wrote: > On Thu, Nov 18, 2010 at 07:19:58AM -0700, Matthew Wilcox wrote: > > I guess I was assuming that, on receiving a FALLOC_FL_PUNCH_HOLE, a > > filesystem that was TRIM-aware would pass that information down to the > > block device that it's mounted on. I strongly feel that we shouldn't > > have two interfaces to do essentially the same thing. > > > > I guess I'm saying that you're going to have to learn about TRIM :-) > > Did you actually look Lukas FITRIM code (not the slight reordering here, > but the original one). It's the ext4 version of the batched discard > model, that is a userspace ioctl to discard free space in the > filesystem. > > hole punching will free the blocks into the free space pool. If you do > online discard it will also get discarded, but a filesystem that has > online discard enabled doesn't need FITRIM. Not stepping into the debate: I'm happy to see punch go to the mapping data and FITRIM pick it up later. However, I think it's time to question whether we actually still want to allow online discard at all. Most of the benchmarks show it to be a net lose to almost everything (either SSD or Thinly Provisioned arrays), so it's become an "enable this to degrade performance" option with no upside. James -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
