largefiles: optimize update speed by only updating changed largefiles
Historically, during 'hg update', every largefile in the working copy was
hashed (which is a very expensive operation on big files) and any
largefiles that did not have a hash that matched their standin were
updated.
This patch optimizes 'hg update' by keeping track of what standins have
changed between the old and new revisions, and only updating the largefiles
that have changed. This saves a lot of time by avoiding the unecessary
calculation of a list of sha1 hashes for big files.
With this patch, the time 'hg update' takes to complete is a function of
how many largefiles need to be updated and what their size is.
Performance tests on a repository with about 80 largefiles ranging from
a few MB to about 97 MB are shown below. The tests show how long it takes
to run 'hg update' with no changes actually being updated.
Mercurial 2.1 release:
$ time hg update
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
getting changed largefiles
0 largefiles updated, 0 removed
real 0m10.045s
user 0m9.367s
sys 0m0.674s
With this patch:
$ time hg update
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
real 0m0.965s
user 0m0.845s
sys 0m0.115s
The same repsoitory, without the largefiles extension enabled:
$ time hg update
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
real 0m0.799s
user 0m0.684s
sys 0m0.111s
So before the patch, 'hg update' with no changes was approximately 9.25s
slower with largefiles enabled. With this patch, it is approximately 0.165s
slower.
from pprint import pprint
from mercurial import minirst
def debugformat(text, form, **kwargs):
if form == 'html':
print "html format:"
out = minirst.format(text, style=form, **kwargs)
else:
print "%d column format:" % form
out = minirst.format(text, width=form, **kwargs)
print "-" * 70
if type(out) == tuple:
print out[0][:-1]
print "-" * 70
pprint(out[1])
else:
print out[:-1]
print "-" * 70
print
def debugformats(title, text, **kwargs):
print "== %s ==" % title
debugformat(text, 60, **kwargs)
debugformat(text, 30, **kwargs)
debugformat(text, 'html', **kwargs)
paragraphs = """
This is some text in the first paragraph.
A small indented paragraph.
It is followed by some lines
containing random whitespace.
\n \n \nThe third and final paragraph.
"""
debugformats('paragraphs', paragraphs)
definitions = """
A Term
Definition. The indented
lines make up the definition.
Another Term
Another definition. The final line in the
definition determines the indentation, so
this will be indented with four spaces.
A Nested/Indented Term
Definition.
"""
debugformats('definitions', definitions)
literals = r"""
The fully minimized form is the most
convenient form::
Hello
literal
world
In the partially minimized form a paragraph
simply ends with space-double-colon. ::
////////////////////////////////////////
long un-wrapped line in a literal block
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
::
This literal block is started with '::',
the so-called expanded form. The paragraph
with '::' disappears in the final output.
"""
debugformats('literals', literals)
lists = """
- This is the first list item.
Second paragraph in the first list item.
- List items need not be separated
by a blank line.
- And will be rendered without
one in any case.
We can have indented lists:
- This is an indented list item
- Another indented list item::
- A literal block in the middle
of an indented list.
(The above is not a list item since we are in the literal block.)
::
Literal block with no indentation (apart from
the two spaces added to all literal blocks).
1. This is an enumerated list (first item).
2. Continuing with the second item.
(1) foo
(2) bar
1) Another
2) List
Line blocks are also a form of list:
| This is the first line.
The line continues here.
| This is the second line.
"""
debugformats('lists', lists)
options = """
There is support for simple option lists,
but only with long options:
-X, --exclude filter an option with a short and long option with an argument
-I, --include an option with both a short option and a long option
--all Output all.
--both Output both (this description is
quite long).
--long Output all day long.
--par This option has two paragraphs in its description.
This is the first.
This is the second. Blank lines may be omitted between
options (as above) or left in (as here).
The next paragraph looks like an option list, but lacks the two-space
marker after the option. It is treated as a normal paragraph:
--foo bar baz
"""
debugformats('options', options)
fields = """
:a: First item.
:ab: Second item. Indentation and wrapping
is handled automatically.
Next list:
:small: The larger key below triggers full indentation here.
:much too large: This key is big enough to get its own line.
"""
debugformats('fields', fields)
containers = """
Normal output.
.. container:: debug
Initial debug output.
.. container:: verbose
Verbose output.
.. container:: debug
Debug output.
"""
debugformats('containers (normal)', containers)
debugformats('containers (verbose)', containers, keep=['verbose'])
debugformats('containers (debug)', containers, keep=['debug'])
debugformats('containers (verbose debug)', containers,
keep=['verbose', 'debug'])
roles = """Please see :hg:`add`."""
debugformats('roles', roles)
sections = """
Title
=====
Section
-------
Subsection
''''''''''
Markup: ``foo`` and :hg:`help`
------------------------------
"""
debugformats('sections', sections)
admonitions = """
.. note::
This is a note
- Bullet 1
- Bullet 2
.. warning:: This is a warning Second
input line of warning
.. danger::
This is danger
"""
debugformats('admonitions', admonitions)
comments = """
Some text.
.. A comment
.. An indented comment
Some indented text.
..
Empty comment above
"""
debugformats('comments', comments)
data = [['a', 'b', 'c'],
['1', '2', '3'],
['foo', 'bar', 'baz this list is very very very long man']]
table = minirst.maketable(data, 2, True)
print table
debugformats('table', table)