compression: introduce an official `format.revlog-compression` option This option supersedes the `experiment.format.compression` option. The value currently supported are zlib (default) and zstd (if Mercurial was compiled with zstd support). The option gained an explicit reference to `revlog` since this is the target usage here. Different storage methods might require different compression strategies. In our tests, using zstd give a significant CPU usage improvement (both compression and decompressing) while keeping similar repository size. Zstd as other interresting mode (dictionnary, pre-text, etc?) that are probably worth exploring. However, just plain switching from zlib to zstd provide a large benefit.

--- a/mercurial/upgrade.py	Tue Apr 02 11:03:46 2019 -0700
+++ b/mercurial/upgrade.py	Wed Mar 27 18:26:54 2019 +0100
@@ -332,7 +332,7 @@
 
     @classmethod
     def fromconfig(cls, repo):
-        return repo.ui.config('experimental', 'format.compression')
+        return repo.ui.config('format', 'revlog-compression')
 
 @registerformatvariant
 class compressionlevel(formatvariant):