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.
#!/usr/bin/env python
# Undump a dump from dumprevlog
# $ hg init
# $ undumprevlog < repo.dump
from __future__ import absolute_import, print_function
import sys
from mercurial import (
encoding,
node,
pycompat,
revlog,
transaction,
vfs as vfsmod,
)
from mercurial.utils import (
procutil,
)
for fp in (sys.stdin, sys.stdout, sys.stderr):
procutil.setbinary(fp)
opener = vfsmod.vfs(b'.', False)
tr = transaction.transaction(sys.stderr.write, opener, {b'store': opener},
b"undump.journal")
while True:
l = sys.stdin.readline()
if not l:
break
if l.startswith("file:"):
f = encoding.strtolocal(l[6:-1])
r = revlog.revlog(opener, f)
pycompat.stdout.write(b'%s\n' % f)
elif l.startswith("node:"):
n = node.bin(l[6:-1])
elif l.startswith("linkrev:"):
lr = int(l[9:-1])
elif l.startswith("parents:"):
p = l[9:-1].split()
p1 = node.bin(p[0])
p2 = node.bin(p[1])
elif l.startswith("length:"):
length = int(l[8:-1])
sys.stdin.readline() # start marker
d = encoding.strtolocal(sys.stdin.read(length))
sys.stdin.readline() # end marker
r.addrevision(d, tr, lr, p1, p2)
tr.close()