view tests/test-obsolete-tag-cache.t @ 42743:8c9a6adec67a

rust-discovery: using the children cache in add_missing

The DAG range computation often needs to get back to very old
revisions, and turns out to be disproportionately long, given
that the end goal is to remove the descendents of the given
missing revisons from the undecided set.

The fast iteration capabilities available in the Rust case make
it possible to avoid the DAG range entirely, at the cost of
precomputing the children cache, and to simply iterate on
children of the given missing revisions.

This is a case where staying on the same side of the interface
between the two languages has clear benefits.

On discoveries with initial undecided sets
small enough to bypass sampling entirely, the total cost of
computing the children cache and the subsequent iteration
becomes better than the Python + C counterpart, which relies on
reachableroots2.

For example, on a repo with more than one million revisions with
an initial undecided set of 11 elements, we get these figures:

Rust version with simple iteration
  addcommons: 57.287us
  first undecided computation: 184.278334ms
  first children cache computation: 131.056us
  addmissings iteration: 42.766us
  first addinfo total: 185.24 ms

Python + C version
  first addcommons: 0.29 ms
  addcommons 0.21 ms
  first undecided computation 191.35 ms
  addmissings 45.75 ms
  first addinfo total: 237.77 ms

On discoveries with large undecided sets, the initial price paid
makes the first addinfo slower than the Python + C version,
but that's more than compensated by the gain in sampling and
subsequent iterations.
Here's an extreme example with an undecided set of a million revisions:

Rust version:
  first undecided computation: 293.842629ms
  first children cache computation: 407.911297ms
  addmissings iteration: 34.312869ms
  first addinfo total: 776.02 ms
  taking initial sample
  query 2: sampling time: 1318.38 ms
  query 2; still undecided: 1005013, sample size is: 200
  addmissings: 143.062us

Python + C version:
  first undecided computation 298.13 ms
  addmissings 80.13 ms
  first addinfo total: 399.62 ms
  taking initial sample
  query 2: sampling time: 3957.23 ms
  query 2; still undecided: 1005013, sample size is: 200
  addmissings 52.88 ms

Differential Revision: https://phab.mercurial-scm.org/D6428

  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > blackbox=
  > rebase=
  > mock=$TESTDIR/mockblackbox.py
  > 
  > [blackbox]
  > track = command, commandfinish, tagscache
  > 
  > [experimental]
  > evolution.createmarkers=True
  > EOF

Create a repo with some tags

  $ hg init repo
  $ cd repo
  $ echo initial > foo
  $ hg -q commit -A -m initial
  $ hg tag -m 'test tag' test1
  $ echo first > first
  $ hg -q commit -A -m first
  $ hg tag -m 'test2 tag' test2
  $ hg -q up -r 0
  $ echo newhead > newhead
  $ hg commit -A -m newhead
  adding newhead
  created new head
  $ hg tag -m 'test head 2 tag' head2

  $ hg log -G -T '{rev}:{node|short} {tags} {desc}\n'
  @  5:2942a772f72a tip test head 2 tag
  |
  o  4:042eb6bfcc49 head2 newhead
  |
  | o  3:c3cb30f2d2cd  test2 tag
  | |
  | o  2:d75775ffbc6b test2 first
  | |
  | o  1:5f97d42da03f  test tag
  |/
  o  0:55482a6fb4b1 test1 initial
  

Trigger tags cache population by doing something that accesses tags info

  $ hg tags
  tip                                5:2942a772f72a
  head2                              4:042eb6bfcc49
  test2                              2:d75775ffbc6b
  test1                              0:55482a6fb4b1

  $ cat .hg/cache/tags2-visible
  5 2942a772f72a444bef4bef13874d515f50fa27b6
  042eb6bfcc4909bad84a1cbf6eb1ddf0ab587d41 head2
  55482a6fb4b1881fa8f746fd52cf6f096bb21c89 test1
  d75775ffbc6bca1794d300f5571272879bd280da test2

Hiding a non-tip changeset should change filtered hash and cause tags recompute

  $ hg debugobsolete -d '0 0' c3cb30f2d2cd0aae008cc91a07876e3c5131fd22 -u dummyuser
  obsoleted 1 changesets

  $ hg tags
  tip                                5:2942a772f72a
  head2                              4:042eb6bfcc49
  test1                              0:55482a6fb4b1

  $ cat .hg/cache/tags2-visible
  5 2942a772f72a444bef4bef13874d515f50fa27b6 f34fbc9a9769ba9eff5aff3d008a6b49f85c08b1
  042eb6bfcc4909bad84a1cbf6eb1ddf0ab587d41 head2
  55482a6fb4b1881fa8f746fd52cf6f096bb21c89 test1

  $ hg blackbox -l 5
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> tags
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> 2/2 cache hits/lookups in * seconds (glob)
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> writing .hg/cache/tags2-visible with 2 tags
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> tags exited 0 after * seconds (glob)
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> blackbox -l 5

Hiding another changeset should cause the filtered hash to change

  $ hg debugobsolete -d '0 0' d75775ffbc6bca1794d300f5571272879bd280da -u dummyuser
  obsoleted 1 changesets
  $ hg debugobsolete -d '0 0' 5f97d42da03fd56f3b228b03dfe48af5c0adf75b -u dummyuser
  obsoleted 1 changesets

  $ hg tags
  tip                                5:2942a772f72a
  head2                              4:042eb6bfcc49

  $ cat .hg/cache/tags2-visible
  5 2942a772f72a444bef4bef13874d515f50fa27b6 2fce1eec33263d08a4d04293960fc73a555230e4
  042eb6bfcc4909bad84a1cbf6eb1ddf0ab587d41 head2

  $ hg blackbox -l 5
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> tags
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> 1/1 cache hits/lookups in * seconds (glob)
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> writing .hg/cache/tags2-visible with 1 tags
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> tags exited 0 after * seconds (glob)
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> blackbox -l 5

Resolving tags on an unfiltered repo writes a separate tags cache

  $ hg --hidden tags
  tip                                5:2942a772f72a
  head2                              4:042eb6bfcc49
  test2                              2:d75775ffbc6b
  test1                              0:55482a6fb4b1

  $ cat .hg/cache/tags2
  5 2942a772f72a444bef4bef13874d515f50fa27b6
  042eb6bfcc4909bad84a1cbf6eb1ddf0ab587d41 head2
  55482a6fb4b1881fa8f746fd52cf6f096bb21c89 test1
  d75775ffbc6bca1794d300f5571272879bd280da test2

  $ hg blackbox -l 5
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> --hidden tags
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> 2/2 cache hits/lookups in * seconds (glob)
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> writing .hg/cache/tags2 with 3 tags
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> --hidden tags exited 0 after * seconds (glob)
  1970/01/01 00:00:00 bob @2942a772f72a444bef4bef13874d515f50fa27b6 (5000)> blackbox -l 5