diff mercurial/help/config.txt @ 42046:4ee906aa7b60

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/help/config.txt	Tue Apr 02 11:03:46 2019 -0700
+++ b/mercurial/help/config.txt	Wed Mar 27 18:26:54 2019 +0100
@@ -866,6 +866,13 @@
     Repositories with this on-disk format require Mercurial version 4.7
 
     Enabled by default.
+``revlog-compression``
+    Compression algorithm used by revlog. Supported value are `zlib` and `zstd`.
+    The `zlib` engine is the historical default of Mercurial. `zstd` is a newer
+    format that is usually a net win over `zlib` operating faster at better
+    compression rate. Use `zstd` to reduce CPU usage.
+
+    On some system, Mercurial installation may lack `zstd` supports. Default is `zlib`.
 
 ``graph``
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