On Wed, Jun 04, 2014 at 10:00:06AM -0400, Chris Mason wrote: > I have a slightly different reason for holding off on these. Disk > format changes are forever, and we need a really strong use case for > pulling them in.
The format upgrade is inevitable for full bidirectional interoperability of filesystems with non-pagesized sectorsize and compression. At the moment this is not possible even without compression, but patches are on the way. > With that said, thanks for spending all of the time on this. Pulling in > Dave's idea to stream larger compression blocks through lzo (or any new > alg) might be enough to push performance much higher, and better show > case the differences between new algorithms. The space savings and speed gains can be measured outside of btrfs. >From the past numbers I see that 4k->64k chunk brings another 5-10% of ratio and the de/compression speed is not worse. Bigger chunks do not improve that much, but the overhead for assembling the linear mappings would be decreased. > The whole reason I chose zlib originally was because its streaming > interface was a better fit for how FS IO worked. Right, zlib has the streaming interface and accepts randomly scattered blocks, but the others do not. LZ4 has a streaming extension proposed, but I haven't looked at it closely whether it satisfies our constraints. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
