On Fri, Aug 11, 2017 at 09:20:10AM -0400, Chris Mason wrote: > > > On 08/10/2017 03:25 PM, Hugo Mills wrote: > > On Thu, Aug 10, 2017 at 01:41:21PM -0400, Chris Mason wrote: > >> On 08/10/2017 04:30 AM, Eric Biggers wrote: > >>> > >>> Theses benchmarks are misleading because they compress the whole file as a > >>> single stream without resetting the dictionary, which isn't how data will > >>> typically be compressed in kernel mode. With filesystem compression the data > >>> has to be divided into small chunks that can each be decompressed independently. > >>> That eliminates one of the primary advantages of Zstandard (support for large > >>> dictionary sizes). > >> > >> I did btrfs benchmarks of kernel trees and other normal data sets as > >> well. The numbers were in line with what Nick is posting here. > >> zstd is a big win over both lzo and zlib from a btrfs point of view. > >> > >> It's true Nick's patches only support a single compression level in > >> btrfs, but that's because btrfs doesn't have a way to pass in the > >> compression ratio. It could easily be a mount option, it was just > >> outside the scope of Nick's initial work. > > > > Could we please not add more mount options? I get that they're easy > > to implement, but it's a very blunt instrument. What we tend to see > > (with both nodatacow and compress) is people using the mount options, > > then asking for exceptions, discovering that they can't do that, and > > then falling back to doing it with attributes or btrfs properties. > > Could we just start with btrfs properties this time round, and cut out > > the mount option part of this cycle. > > > > In the long run, it'd be great to see most of the btrfs-specific > > mount options get deprecated and ultimately removed entirely, in > > favour of attributes/properties, where feasible. > > > > It's a good point, and as was commented later down I'd just do mount -o > compress=zstd:3 or something. We've solved that already, here's a proposed patch that extends current mount options, https://www.mail-archive.com/linux-btrfs@xxxxxxxxxxxxxxx/msg66248.html and a patch that could be backported to older kernels so the new mount options do not break mounts on older kernels with the new syntax https://patchwork.kernel.org/patch/9845697/
