annotate contrib/plan9/mkfile @ 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

APE=/sys/src/ape
<$APE/config

PYTHON=python
PYTHONBIN=/rc/bin
SH=ape/psh

PURE=--pure
ROOT=../..

# This is slightly underhanded; Plan 9 does not support GNU gettext nor
# does it support dynamically loaded extension modules. We work around
# this by calling build_py and build_scripts directly; this avoids
# additional platform hacks in setup.py.
build:VQ:
	@{
		cd $ROOT
		$SH -c '$PYTHON setup.py $PURE build_py build_scripts'
	}

clean:VQ:
	@{
		cd $ROOT
		$SH -c '$PYTHON setup.py $PURE clean --all'
	}

install:VQ:	build
	@{
		cd $ROOT
		$SH -c '$PYTHON setup.py $PURE install \
			--install-scripts $PYTHONBIN \
			--skip-build \
			--force'
	}
	mkdir -p /lib/mercurial/hgrc.d
	dircp hgrc.d /lib/mercurial/hgrc.d/
	cp 9diff /rc/bin/