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
# memory.py - track memory usage
#
# Copyright 2009 Olivia Mackall <olivia@selenic.com> and others
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
'''helper extension to measure memory usage
Reads current and peak memory usage from ``/proc/self/status`` and
prints it to ``stderr`` on exit.
'''
from __future__ import absolute_import
def memusage(ui):
"""Report memory usage of the current process."""
result = {'peak': 0, 'rss': 0}
with open('/proc/self/status', 'r') as status:
# This will only work on systems with a /proc file system
# (like Linux).
for line in status:
parts = line.split()
key = parts[0][2:-1].lower()
if key in result:
result[key] = int(parts[1])
ui.write_err(
", ".join(
["%s: %.1f MiB" % (k, v / 1024.0) for k, v in result.iteritems()]
)
+ "\n"
)
def extsetup(ui):
ui.atexit(memusage, ui)