# HG changeset patch
# User Georges Racinet <georges.raci...@octobus.net>
# Date 1622935470 -7200
# Sun Jun 06 01:24:30 2021 +0200
# Branch stable
# Node ID be560b55eb7cfe25c68fb6fab5417fab6688cf84
# Parent 5ac0f2a8ba7205266a206ad8da89a79173e8efea
# EXP-Topic memleak-phases
cext: fix memory leak in phases computation
Without this a buffer whose size in bytes is the number of
changesets in the repository is leaked each time the repository is
opened and changeset phases are computed.
Impact: the current code in hgwebdir creates a new `localrepository`
instance for each HTTP request. Since any pull or push is made of several
requests, a team of 100 people can easily produce thousands of such
requests per day.
Being a low-level malloc, this leak can't be seen with the gc module and
tools relying on that, but was spotted by valgrind immediately.
Reproduction
------------
for i in range(cl_args.iterations):
repo = hg.repository(baseui, repo_path)
rev = repo.revs(rev).first()
ctx = repo[rev]
del ctx
del repo
# avoid any pollution by other type of leak
# (that should be fixed in 5.8)
repoview._filteredrepotypes.clear()
gc.collect()
Measurements
------------
Resident Set Size (RSS), taken on a clone of
mozilla-central for performance analysis (440 000
changesets).
before:
5.8+hg19.5ac0f2a8ba72 1000 iterations: 1606MB
5.8+hg19.5ac0f2a8ba72 10000 iterations: 5723MB
after:
5.8+hg20.e2084d39e145 1000 iterations: 555MB
5.8+hg20.e2084d39e145 10000 iterations: 555MB
(double checked, not a copy/paste error)
(e2084d39e14 is the present changeset, before amendment
of the message to add the measurements)
diff -r 5ac0f2a8ba72 -r be560b55eb7c mercurial/cext/revlog.c
--- a/mercurial/cext/revlog.c Thu May 20 14:20:39 2021 -0400
+++ b/mercurial/cext/revlog.c Sun Jun 06 01:24:30 2021 +0200
@@ -919,6 +919,7 @@
phasesets[i] = NULL;
}
+ free(phases);
return Py_BuildValue("nN", len, phasesetsdict);
release:
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