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bb461d2240
Summary:
If there are too many heads, the current `descendants` algorithm would visit
all "old" heads. For example, with this graph:
head9999 (N9999)
/
Z (master)
:
: (many heads)
:/
: head2 (N2)
:/
C head1 (N1)
|/
B head0 (N0)
|/
A
`A::head9999` or `Z::head9999` will visit N0, N1, ..., N9999, because
`descendands_up_to` is provided with `max_id = N9999` and Z as a vertex in the
master group, is before N0 in non-master. The current algorithm also means
`descendands_up_to` gets linearly slower as the user uses the repo more, which
is quite undesirable.
This diff changes `descendands_up_to` to take an `ancestors` set, which is
`::head9999` in this case, and iterate non-master flat segments in it. So it
will skip N0 to N9998 directly by finding the N9999 flat segment and only use
it. The number of heads will have a smaller impact on performance.
Another slowness is `draft::draft_heads`, if there are too many `draft_heads`,
the internal calculation of `::draft_heads` can be slow. Optimize it by
limiting `draft_heads` to `draft:`. Practically this affects `y::` revset as
`y::` is translated to `y::visible_heads` and `visible_heads` can be large.
`cargo bench --bench dag_ops -- '::-master'` shows significant difference:
Before:
range (master::draft) 18.112 s
range (recent_draft::drafts) 2.594 s
After:
range (master::draft) 72.542 ms
range (recent_draft::drafts) 14.932 ms
In my fbsource checkout there were 20k+ heads. The improvement of
`master::recent_draft` (`x::y`) is pretty visible, and `y::` is also improved:
% lhg debugbenchmarkrevsets -m -x 'p1(min(7e8c86ae % master))' -Y 'draft() & 7e8c86ae' -e 'x::y' -e 'y::' --no-default
# x: 168f5228e570fb6b2ff7f851bd82413102748d84 (p1(min(7e8c86ae % master)))
# y: 7e8c86aec68ebc6e0b8254afcb381315991fd21c (draft() & 7e8c86ae)
# before
| revset \ backend | segments | revlog | revlog-cpy |
|------------------|----------|--------|------------|
| x::y | 17ms | 0.1ms | 0.5ms |
| y:: | 3.3ms | 0.7ms | 1.3ms |
# after
| revset \ backend | segments | revlog | revlog-cpy |
|------------------|----------|--------|------------|
| x::y | 0.2ms | 0.1ms | 0.6ms |
| y:: | 1.0ms | 0.7ms | 1.3ms |
Reviewed By: sfilipco
Differential Revision: D23214387
fbshipit-source-id: 4d11db84cd28f4e04e8b991cbc650c9d5781fd27
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| .. | ||
| contrib | ||
| distutils_rust | ||
| doc | ||
| edenscm | ||
| edenscmnative | ||
| exec | ||
| hgcache_size_logger | ||
| i18n | ||
| lib | ||
| newdoc | ||
| pystubs | ||
| slides | ||
| tests | ||
| .editorconfig | ||
| .flake8 | ||
| .gitignore | ||
| COPYING | ||
| gen_version.py | ||
| hgeditor | ||
| Makefile | ||
| README.rst | ||
| setup3.py | ||
| setup.py | ||
Mercurial ========= Mercurial is a fast, easy to use, distributed revision control tool for software developers. Basic install:: $ make # see install targets $ make install # do a system-wide install $ hg debuginstall # sanity-check setup $ hg # see help Running without installing:: $ make local # build for inplace usage $ ./hg --version # should show the latest version See https://mercurial-scm.org/ for detailed installation instructions, platform-specific notes, and Mercurial user information.