view tests/fakemergerecord.py @ 47120:7109a38830c9

dirstate-tree: Fold "tracked descendants" counter update in main walk

For the purpose of implementing `has_tracked_dir` (which means "has tracked
descendants) without an expensive sub-tree traversal, we maintaing a counter
of tracked descendants on each "directory" node of the tree-shaped dirstate.

Before this changeset, mutating or inserting a node at a given path would
involve:

* Walking the tree from root through ancestors to find the node or the spot
  where to insert it
* Looking at the previous node if any to decide what counter update is needed
* Performing any node mutation
* Walking the tree *again* to update counters in ancestor nodes

When profiling `hg status` on a large repo, this second walk takes times
while loading a the dirstate from disk.

It turns out we have enough information to decide before he first tree walk
what counter update is needed. This changeset merges the two walks, gaining
~10% of the total time for `hg update` (in the same hyperfine benchmark as
the previous changeset).

---

Profiling was done by compiling with this `.cargo/config`:

    [profile.release]
    debug = true

then running with:

    py-spy record -r 500 -n -o /tmp/hg.json --format speedscope -- \
    ./hg status -R $REPO --config experimental.dirstate-tree.in-memory=1

then visualizing the recorded JSON file in https://www.speedscope.app/

Differential Revision: https://phab.mercurial-scm.org/D10554

# Extension to write out fake unsupported records into the merge state
#
#

from __future__ import absolute_import

from mercurial import (
    mergestate as mergestatemod,
    registrar,
)

cmdtable = {}
command = registrar.command(cmdtable)


@command(
    b'fakemergerecord',
    [
        (b'X', b'mandatory', None, b'add a fake mandatory record'),
        (b'x', b'advisory', None, b'add a fake advisory record'),
    ],
    '',
)
def fakemergerecord(ui, repo, *pats, **opts):
    with repo.wlock():
        ms = mergestatemod.mergestate.read(repo)
        records = ms._makerecords()
        if opts.get('mandatory'):
            records.append((b'X', b'mandatory record'))
        if opts.get('advisory'):
            records.append((b'x', b'advisory record'))
        ms._writerecords(records)