match: making visitdir() deal with non-recursive entries
Primarily as an optimization to avoid recursing into directories that will
never have a match inside, this classifies each matcher pattern's root as
recursive or non-recursive (erring on the side of keeping it recursive,
which may lead to wasteful directory or manifest walks that yield no matches).
I measured the performance of "rootfilesin" in two repos:
- The Firefox repo with tree manifests, with
"hg files -r . -I rootfilesin:browser".
The browser directory contains about 3K files across 249 subdirectories.
- A specific Google-internal directory which contains 75K files across 19K
subdirectories, with "hg files -r . -I rootfilesin:REDACTED".
I tested with both cold and warm disk caches. Cold cache was produced by
running "sync; echo 3 > /proc/sys/vm/drop_caches". Warm cache was produced
by re-running the same command a few times.
These were the results:
Cold cache Warm cache
Before After Before After
firefox 0m5.1s 0m2.18s 0m0.22s 0m0.14s
google3 dir 2m3.9s 0m1.57s 0m8.12s 0m0.16s
Certain extensions, notably narrowhg, can depend on this for correctness
(not trying to recurse into directories for which it has no information).
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.