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
Test hg log changeset printer external hook
-------------------------------------------
$ cat > $TESTTMP/logexthook.py <<EOF
> from __future__ import absolute_import
> import codecs
> from mercurial import (
> commands,
> logcmdutil,
> repair,
> )
> def brot13(b):
> return codecs.encode(b.decode('utf8'), 'rot-13').encode('utf8')
> def rot13description(self, ctx):
> description = ctx.description().strip().splitlines()[0]
> self.ui.write(b"%s: %s\n" % (brot13(b"summary"),
> brot13(description)))
> def reposetup(ui, repo):
> logcmdutil.changesetprinter._exthook = rot13description
> EOF
Prepare the repository
$ hg init empty
$ cd empty
$ touch ROOT
$ hg commit -A -m "Root" ROOT
$ touch a b c
$ hg commit -A -m "Add A, B, C" a b c
Check the log
$ hg log --config extensions.t=$TESTTMP/logexthook.py
changeset: 1:70fc82b23320
tag: tip
user: test
date: Thu Jan 01 00:00:00 1970 +0000
fhzznel: Nqq N, O, P
summary: Add A, B, C
changeset: 0:b00443a54871
user: test
date: Thu Jan 01 00:00:00 1970 +0000
fhzznel: Ebbg
summary: Root
Check that exthook is working with graph log too
$ hg log -G --config extensions.t=$TESTTMP/logexthook.py
@ changeset: 1:70fc82b23320
| tag: tip
| user: test
| date: Thu Jan 01 00:00:00 1970 +0000
| fhzznel: Nqq N, O, P
| summary: Add A, B, C
|
o changeset: 0:b00443a54871
user: test
date: Thu Jan 01 00:00:00 1970 +0000
fhzznel: Ebbg
summary: Root