Mercurial > hg
view tests/test-tools.t @ 47802:de2e04fe4897
hgwebdir: avoid systematic full garbage collection
Forcing a systematic full garbage collection upon each request
can serioulsy harm performance. This is reported as
https://bz.mercurial-scm.org/show_bug.cgi?id=6075
With this change we're performing the full collection according
to a new setting, `experimental.web.full-garbage-collection-rate`.
The default value is 1, which doesn't change the behavior and will
allow us to test on real use cases. If the value is 0, no full garbage
collection occurs.
Regardless of the value of the setting, a partial garbage collection
still occurs upon each request (not attempting to collect objects from
the oldest generation). This should be enough to take care of
reference cycles that have been created by the last request
(assessment of this requires changing the setting, not to be 1).
In my experience chasing memory leaks in Mercurial servers,
the full collection never reclaimed any memory, but this is with
Python 3 and biased towards small repositories.
On the other hand, as explained in the Python developer docs [1],
frequent full collections are very harmful in terms of performance if
lots of objects survive the collection, and hence stay in the
oldest generation. Note that `gc.collect()` is indeed trying to
collect the oldest generation [2]. This happens usually in two cases:
- unwanted lingering objects (i.e., an actual memory leak that
the GC cannot do anything about). Sadly, we have lots of those
these days.
- desireable long-term objects, typically in caches (not inner caches
carried by repositories, which should be collected with them). This
is a subject of interest for the Heptapod project.
In short, the flat rate that this change still permits is
probably a bad idea in most cases, and the default value can
be tweaked later on (or even be set to 0) according to experiments
in the wild.
The test is inspired from test-hgwebdir-paths.py
[1] https://devguide.python.org/garbage_collector/#collecting-the-oldest-generation
[2] https://docs.python.org/3/library/gc.html#gc.collect
Differential Revision: https://phab.mercurial-scm.org/D11204
author | Georges Racinet <georges.racinet@octobus.net> |
---|---|
date | Tue, 20 Jul 2021 17:20:19 +0200 |
parents | 5abc47d4ca6b |
children | 9172bd49cedc |
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Tests of the file helper tool $ f -h ?sage: f [options] [filenames] (glob) ?ptions: (glob) -h, --help show this help message and exit -t, --type show file type (file or directory) -m, --mode show file mode -l, --links show number of links -s, --size show size of file -n NEWER, --newer=NEWER check if file is newer (or same) -r, --recurse recurse into directories -S, --sha1 show sha1 hash of the content --sha256 show sha256 hash of the content -M, --md5 show md5 hash of the content -D, --dump dump file content -H, --hexdump hexdump file content -B BYTES, --bytes=BYTES number of characters to dump -L LINES, --lines=LINES number of lines to dump -q, --quiet no default output $ mkdir dir $ cd dir $ f --size size=0 $ echo hello | f --md5 --size size=6, md5=b1946ac92492d2347c6235b4d2611184 $ f foo foo: file not found $ echo foo > foo $ f foo foo: $ f --sha1 foo foo: sha1=f1d2d2f924e986ac86fdf7b36c94bcdf32beec15 $ f --sha256 foo foo: sha256=b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c #if symlink $ f foo --mode foo: mode=644 #endif #if no-windows $ "$PYTHON" $TESTDIR/seq.py 10 > bar #else Convert CRLF -> LF for consistency $ "$PYTHON" $TESTDIR/seq.py 10 | sed "s/$//" > bar #endif #if unix-permissions symlink $ chmod +x bar $ f bar --newer foo --mode --type --size --dump --links --bytes 7 bar: file, size=21, mode=755, links=1, newer than foo >>> 1 2 3 4 <<< no trailing newline #endif #if unix-permissions $ ln bar baz $ f bar -n baz -l --hexdump -t --sha1 --lines=9 -B 20 bar: file, links=2, newer than baz, sha1=612ca68d0305c821750a 0000: 31 0a 32 0a 33 0a 34 0a 35 0a 36 0a 37 0a 38 0a |1.2.3.4.5.6.7.8.| 0010: 39 0a |9.| $ rm baz #endif #if unix-permissions symlink $ ln -s yadda l $ f . --recurse -MStmsB4 .: directory with 3 files, mode=755 ./bar: file, size=21, mode=755, md5=3b03, sha1=612c ./foo: file, size=4, mode=644, md5=d3b0, sha1=f1d2 ./l: link, size=5, md5=2faa, sha1=af93 #endif $ f --quiet bar -DL 3 1 2 3 $ cd .. Yadda is a symlink $ f -qr dir -HB 17 dir: directory with 3 files (symlink !) dir: directory with 2 files (no-symlink !) dir/bar: 0000: 31 0a 32 0a 33 0a 34 0a 35 0a 36 0a 37 0a 38 0a |1.2.3.4.5.6.7.8.| 0010: 39 |9| dir/foo: 0000: 66 6f 6f 0a |foo.| dir/l: (symlink !) 0000: 79 61 64 64 61 |yadda| (symlink !)