phases: rework the logic of _pushdiscoveryphase to bound complexity This rework the various graph traversal in _pushdiscoveryphase to keep the complexity in check. This is done though a couple of things: - first, limiting the space we have to explore, for example, if we are not in publishing push, we don't need to consider remote draft roots that are also draft locally, as there is nothing to be moved there. - avoid unbounded descendant computation, and use the faster "rev between" computation. This provide a massive boost to performance when exchanging with repository with a massive amount of draft, like mozilla-try: ### data-env-vars.name = mozilla-try-2023-03-22-zstd-sparse-revlog # benchmark.name = hg.command.push # bin-env-vars.hg.flavor = default # bin-env-vars.hg.py-re2-module = default # benchmark.variants.explicit-rev = all-out-heads # benchmark.variants.issue6528 = disabled # benchmark.variants.protocol = ssh # benchmark.variants.reuse-external-delta-parent = default ## benchmark.variants.revs = any-1-extra-rev before: 20.346590 seconds after: 11.232059 seconds (-38.15%, -7.48 seconds) ## benchmark.variants.revs = any-100-extra-rev before: 24.752051 seconds after: 15.367412 seconds (-37.91%, -9.38 seconds) After this changes, the push operation is still quite too slow. Some of this can be attributed to general phases slowness (reading all the roots from disk for example) and other know slowness (not using persistent-nodemap, branchmap, tags, etc. We are also working on them, but with this series, phase discovery during push no longer showing up in profile and this is a pretty nice and bit low-hanging fruit out of the way. ### (same case as the above) # benchmark.variants.revs = any-1-extra-rev pre-%ln-change: 44.235070 this-changeset: 11.232059 seconds (-74.61%, -33.00 seconds) # benchmark.variants.revs = any-100-extra-rev pre-%ln-change: 49.234697 this-changeset: 15.367412 seconds (-68.79%, -33.87 seconds) Note that with this change, the `hg push` performance is now much closer to the `hg pull` performance, even it still lagging behind a bit. (and the overall performance are still too slow). ### data-env-vars.name = mozilla-try-2023-03-22-ds2-pnm # benchmark.variants.explicit-rev = all-out-heads # benchmark.variants.issue6528 = disabled # benchmark.variants.protocol = ssh # benchmark.variants.pulled-delta-reuse-policy = default # bin-env-vars.hg.flavor = rust ## benchmark.variants.revs = any-1-extra-rev hg.command.pull: 6.517450 hg.command.push: 11.219888 ## benchmark.variants.revs = any-100-extra-rev hg.command.pull: 10.160991 hg.command.push: 14.251107 ### data-env-vars.name = mozilla-try-2023-03-22-zstd-sparse-revlog # bin-env-vars.hg.py-re2-module = default # benchmark.variants.explicit-rev = all-out-heads # benchmark.variants.issue6528 = disabled # benchmark.variants.protocol = ssh # benchmark.variants.pulled-delta-reuse-policy = default ## bin-env-vars.hg.flavor = default ## benchmark.variants.revs = any-1-extra-rev hg.command.pull: 8.577772 hg.command.push: 11.232059 ## bin-env-vars.hg.flavor = default ## benchmark.variants.revs = any-100-extra-rev hg.command.pull: 13.152976 hg.command.push: 15.367412 ## bin-env-vars.hg.flavor = rust ## benchmark.variants.revs = any-1-extra-rev hg.command.pull: 8.731982 hg.command.push: 11.178751 ## bin-env-vars.hg.flavor = rust ## benchmark.variants.revs = any-100-extra-rev hg.command.pull: 13.184236 hg.command.push: 15.620843

This test cover a bug that no longer exist.

Define helpers.

  $ hg_log () { hg log -G -T "{rev}:{node|short}"; }
  $ commit () { echo "foo - ${2:-$1}" > $1; hg commit -Aqm "Edited $1"; }
  $ strip() { hg --config extensions.strip= strip -q -r "$1" ; }

Setup hg repo.

  $ hg init repo
  $ cd repo
  $ touch x; hg add x; hg commit -m "initial"
  $ hg clone -q . ../clone
  $ commit a

  $ cd ../clone

  $ commit b

  $ hg pull -q ../repo

  $ ls -1 .hg/cache/branch?*
  .hg/cache/branch2-base
  .hg/cache/branch2-served
  $ cat .hg/cache/branch?-served
  222ae9789a75703f9836e44de7db179cbfd420ee 2
  a3498d6e39376d2456425dd8c692367bdbf00fa2 o default
  222ae9789a75703f9836e44de7db179cbfd420ee o default

  $ hg_log
  o  2:222ae9789a75
  |
  | @  1:a3498d6e3937
  |/
  o  0:7ab0a3bd758a
  

  $ strip '1:'

After the strip the "served" cache is now identical to the "base" one, and the
older one have been actively deleted.

  $ ls -1 .hg/cache/branch?*
  .hg/cache/branch2-base
  $ cat .hg/cache/branch?-base
  7ab0a3bd758a58b9f79557ce708533e627776cce 0
  7ab0a3bd758a58b9f79557ce708533e627776cce o default

We do a new commit and we get a new valid branchmap for the served version

  $ commit c
  $ ls -1 .hg/cache/branch?*
  .hg/cache/branch2-base
  .hg/cache/branch2-served
  $ cat .hg/cache/branch?-served
  a1602b357cfca067600406eb19060c7128804d72 1
  a1602b357cfca067600406eb19060c7128804d72 o default


On pull we end up with the same tip, and so wrongly reuse the invalid cache and crash.

  $ hg pull ../repo --quiet
  $ hg heads -T '{rev} {node} {branch}\n'
  2 222ae9789a75703f9836e44de7db179cbfd420ee default
  1 a1602b357cfca067600406eb19060c7128804d72 default
  $ ls -1 .hg/cache/branch?*
  .hg/cache/branch2-base
  .hg/cache/branch2-served
  $ cat .hg/cache/branch?-served
  222ae9789a75703f9836e44de7db179cbfd420ee 2
  a1602b357cfca067600406eb19060c7128804d72 o default
  222ae9789a75703f9836e44de7db179cbfd420ee o default