view hgweb.cgi @ 51377:02e7d79edf62

branchmap: use mmap for faster revbranchcache loading

A typical revbranchmap usage is:
- load the entire revbranchmap file into memory
- maybe do a few lookups
- add a few bytes to it
- write the addition to disk

There's no reason to load the entire revbranchmap into memory.
We can split it into a large immutable prefix and a mutable suffix,
and then memorymap the prefix, thus saving all the useless loading.

Benchmarking on some real-world pushes suggests that out of ~100s server-side
push handling revbranchcache handling is responsible for:

* ~7s with no change
* ~1.3s with the change, without mmap
* 0.04s with the change, with mmap

#!/usr/bin/env python3
#
# An example hgweb CGI script, edit as necessary
# See also https://mercurial-scm.org/wiki/PublishingRepositories

# Path to repo or hgweb config to serve (see 'hg help hgweb')
config = b"/path/to/repo/or/config"

# Uncomment and adjust if Mercurial is not installed system-wide
# (consult "installed modules" path from 'hg debuginstall'):
# import sys; sys.path.insert(0, "/path/to/python/lib")

from mercurial import demandimport

demandimport.enable()
from mercurial.hgweb import hgweb, wsgicgi

application = hgweb(config)
wsgicgi.launch(application)