view mercurial/help/extensions.txt @ 27258:beda2c9dbbff

repoview: bypass changelog method to computed cache key

Getting the data necessary for the cache key using the changelog/revlog method
adds a significant overhead. Given how simple the underlying implementation is
and often this code is ran, it makes sense to violate layering and directly
compute the data.

Testing `hg log` on Mozilla-central, this reduce the time spent on changelog
cache validation by an extra half:

before: 12.2s of 69s
after:   6.1s of 62s

Total speed up from this patch and it's parent is 3x

(With stupid python profiler overhead)

The global speedup without profiler overhead is still there,

Before: 51s
After:  39s (-23%)

Mercurial has the ability to add new features through the use of
extensions. Extensions may add new commands, add options to
existing commands, change the default behavior of commands, or
implement hooks.

To enable the "foo" extension, either shipped with Mercurial or in the
Python search path, create an entry for it in your configuration file,
like this::

  [extensions]
  foo =

You may also specify the full path to an extension::

  [extensions]
  myfeature = ~/.hgext/myfeature.py

See :hg:`help config` for more information on configuration files.

Extensions are not loaded by default for a variety of reasons:
they can increase startup overhead; they may be meant for advanced
usage only; they may provide potentially dangerous abilities (such
as letting you destroy or modify history); they might not be ready
for prime time; or they may alter some usual behaviors of stock
Mercurial. It is thus up to the user to activate extensions as
needed.

To explicitly disable an extension enabled in a configuration file of
broader scope, prepend its path with !::

  [extensions]
  # disabling extension bar residing in /path/to/extension/bar.py
  bar = !/path/to/extension/bar.py
  # ditto, but no path was supplied for extension baz
  baz = !