view tests/helpers-testrepo.sh @ 44363:f7459da77f23

nodemap: introduce an option to use mmap to read the nodemap mapping

The performance and memory benefit is much greater if we don't have to copy all
the data in memory for each information. So we introduce an option (on by
default) to read the data using mmap.

This changeset is the last one definition the API for index support nodemap
data. (they have to be able to use the mmaping).

Below are some benchmark comparing the best we currently have in 5.3 with the
final step of this series (using the persistent nodemap implementation in
Rust). The benchmark run `hg perfindex` with various revset and the following
variants:

Before:

 * do not use the persistent nodemap
 * use the CPython implementation of the index for nodemap
 * use mmapping of the changelog index

After:

 * use the MixedIndex Rust code, with the NodeTree object for nodemap access
   (still in review)
 * use the persistent nodemap data from disk
 * access the persistent nodemap data through mmap
 * use mmapping of the changelog index

The persistent nodemap greatly speed up  most operation on very large
repositories. Some of the previously very fast lookup end up a bit slower because
the persistent nodemap has to be setup. However the absolute slowdown is very
small and won't matters in the big picture.

Here are some numbers (in seconds) for the reference copy of mozilla-try:

Revset            Before   After     abs-change speedup

-10000:           0.004622 0.005532   0.000910  ×   0.83
-10:              0.000050 0.000132   0.000082  ×   0.37
tip               0.000052 0.000085   0.000033  ×   0.61
0 + (-10000:)     0.028222 0.005337  -0.022885  ×   5.29
0                 0.023521 0.000084  -0.023437  × 280.01
(-10000:) + 0     0.235539 0.005308  -0.230231  ×  44.37
(-10:) + :9       0.232883 0.000180  -0.232703  ×1293.79
(-10000:) + (:99) 0.238735 0.005358  -0.233377  ×  44.55
:99 + (-10000:)   0.317942 0.005593  -0.312349  ×  56.84
:9 + (-10:)       0.313372 0.000179  -0.313193  ×1750.68
:9                0.316450 0.000143  -0.316307  ×2212.93


On smaller repositories, the cost of nodemap related operation is not as big, so
the win is much more modest. Yet it helps shaving a handful of millisecond here
and there.

Here are some numbers (in seconds) for the reference copy of mercurial:

Revset            Before   After     abs-change speedup
-10:              0.000065 0.000097   0.000032  × 0.67
tip               0.000063 0.000078   0.000015  × 0.80
0                 0.000561 0.000079  -0.000482  × 7.10
-10000:           0.004609 0.003648  -0.000961  × 1.26
0 + (-10000:)     0.005023 0.003715  -0.001307  × 1.35
(-10:) + :9       0.002187 0.000108  -0.002079  ×20.25
(-10000:) + 0     0.006252 0.003716  -0.002536  × 1.68
(-10000:) + (:99) 0.006367 0.003707  -0.002660  × 1.71
:9 + (-10:)       0.003846 0.000110  -0.003736  ×34.96
:9                0.003854 0.000099  -0.003755  ×38.92
:99 + (-10000:)   0.007644 0.003778  -0.003866  × 2.02

Differential Revision: https://phab.mercurial-scm.org/D7894

# In most cases, the mercurial repository can be read by the bundled hg, but
# that isn't always true because third-party extensions may change the store
# format, for example. In which case, the system hg installation is used.
#
# We want to use the hg version being tested when interacting with the test
# repository, and the system hg when interacting with the mercurial source code
# repository.
#
# The mercurial source repository was typically orignally cloned with the
# system mercurial installation, and may require extensions or settings from
# the system installation.

if [ -n "$HGTESTEXTRAEXTENSIONS" ]; then
    for extension in $HGTESTEXTRAEXTENSIONS; do
        extraoptions="$extraoptions --config extensions.$extension=!"
    done
fi

syshg () {
    (
        syshgenv
        exec hg "$@"
    )
}

# Revert the environment so that running "hg" runs the system hg
# rather than the test hg installation.
syshgenv () {
    . "$HGTEST_RESTOREENV"
    HGPLAIN=1
    export HGPLAIN
}

# The test-repo is a live hg repository which may have evolution markers
# created, e.g. when a ~/.hgrc enabled evolution.
#
# Tests may be run using a custom HGRCPATH, which do not enable evolution
# markers by default.
#
# If test-repo includes evolution markers, and we do not enable evolution
# markers, hg will occasionally complain when it notices them, which disrupts
# tests resulting in sporadic failures.
#
# Since we aren't performing any write operations on the test-repo, there's
# no harm in telling hg that we support evolution markers, which is what the
# following lines for the hgrc file do:
cat >> "$HGRCPATH" << EOF
[experimental]
evolution = createmarkers
EOF

# Use the system hg command if the bundled hg can't read the repository with
# no warning nor error.
if [ -n "`hg id -R "$TESTDIR/.." 2>&1 >/dev/null`" ]; then
    alias testrepohg=syshg
    alias testrepohgenv=syshgenv
else
    alias testrepohg="hg $extraoptions"
    alias testrepohgenv=:
fi