view tests/test-run-tests.py @ 33207:895ecec31c70

revlog: add an experimental option to mitigated delta issues (issue5480)

The general delta heuristic to select a delta do not scale with the number of
branch. The delta base is frequently too far away to be able to reuse a chain
according to the "distance" criteria. This leads to insertion of larger delta (or
even full text) that themselves push the bases for the next delta further away
leading to more large deltas and full texts. This full text and frequent
recomputation throw Mercurial performance in disarray.

For example of a slightly large repository

  280 000 files (2 150 000 versions)
  430 000 changesets (10 000 topological heads)

Number below compares repository with and without the distance criteria:

manifest size:
    with:    21.4 GB
    without:  0.3 GB

store size:
    with:    28.7 GB
    without   7.4 GB

bundle last 15 00 revisions:
    with:    800 seconds
             971 MB
    without:  50 seconds
              73 MB

unbundle time (of the last 15K revisions):
    with:    1150 seconds (~19 minutes)
    without:   35 seconds

Similar issues has been observed in other repositories.


Adding a new option or "feature" on stable is uncommon. However, given that this
issues is making Mercurial practically unusable, I'm exceptionally targeting
this patch for stable.

What is actually needed is a full rework of the delta building and reading
logic. However, that will be a longer process and churn not suitable for stable.

In the meantime, we introduces a quick and dirty mitigation of this in the
'experimental' config space. The new option introduces a way to set the maximum
amount of memory usable to store a diff in memory. This extend the ability for
Mercurial to create chains without removing all safe guard regarding memory
access. The option should be phased out when core has a more proper solution
available.

Setting the limit to '0' remove all limits, setting it to '-1' use the default
limit (textsize x 4).

"""test line matching with some failing examples and some which warn

run-test.t only checks positive matches and can not see warnings
(both by design)
"""
from __future__ import absolute_import, print_function

import doctest
import os
import re
# this is hack to make sure no escape characters are inserted into the output
if 'TERM' in os.environ:
    del os.environ['TERM']
run_tests = __import__('run-tests')

def prn(ex):
    m = ex.args[0]
    if isinstance(m, str):
        print(m)
    else:
        print(m.decode('utf-8'))

def lm(expected, output):
    r"""check if output matches expected

    does it generally work?
        >>> lm(b'H*e (glob)\n', b'Here\n')
        True

    fail on bad test data
        >>> try: lm(b'a\n',b'a')
        ... except AssertionError as ex: print(ex)
        missing newline
        >>> try: lm(b'single backslash\n', b'single \backslash\n')
        ... except AssertionError as ex: prn(ex)
        single backslash or unknown char
    """
    assert (expected.endswith(b'\n')
            and output.endswith(b'\n')), 'missing newline'
    assert not re.search(br'[^ \w\\/\r\n()*?]', expected + output), \
           b'single backslash or unknown char'
    match = run_tests.TTest.linematch(expected, output)
    if isinstance(match, str):
        return 'special: ' + match
    elif isinstance(match, bytes):
        return 'special: ' + match.decode('utf-8')
    else:
        return bool(match) # do not return match object

def wintests():
    r"""test matching like running on windows

    enable windows matching on any os
        >>> _osaltsep = os.altsep
        >>> os.altsep = True

    valid match on windows
        >>> lm(b'g/a*/d (glob)\n', b'g\\abc/d\n')
        True

    direct matching, glob unnecessary
        >>> lm(b'g/b (glob)\n', b'g/b\n')
        'special: -glob'

    missing glob
        >>> lm(b'/g/c/d/fg\n', b'\\g\\c\\d/fg\n')
        'special: +glob'

    restore os.altsep
        >>> os.altsep = _osaltsep
    """
    pass

def otherostests():
    r"""test matching like running on non-windows os

    disable windows matching on any os
        >>> _osaltsep = os.altsep
        >>> os.altsep = False

    backslash does not match slash
        >>> lm(b'h/a* (glob)\n', b'h\\ab\n')
        False

    direct matching glob can not be recognized
        >>> lm(b'h/b (glob)\n', b'h/b\n')
        True

    missing glob can not not be recognized
        >>> lm(b'/h/c/df/g/\n', b'\\h/c\\df/g\\\n')
        False

    restore os.altsep
        >>> os.altsep = _osaltsep
    """
    pass

if __name__ == '__main__':
    doctest.testmod()