dirstate-tree: Avoid BTreeMap double-lookup when inserting a dirstate entry
The child nodes of a given node in the tree-shaped dirstate are kept in a
`BTreeMap` where keys are file names as strings. Finding or inserting a value
in the map takes `O(log(n))` string comparisons, which adds up when constructing
the tree.
The `entry` API allows finding a "spot" in the map that may or may not be
occupied and then access that value or insert a new one without doing map
lookup again. However the current API is limited in that calling `entry`
requires an owned key (and so a memory allocation), even if it ends up not
being used in the case where the map already has a value with an equal key.
This is still a win, with 4% better end-to-end time for `hg status` measured
here with hyperfine:
```
Benchmark #1: ../hg2/hg status -R $REPO --config=experimental.dirstate-tree.in-memory=1
Time (mean ± σ): 1.337 s ± 0.018 s [User: 892.9 ms, System: 437.5 ms]
Range (min … max): 1.316 s … 1.373 s 10 runs
Benchmark #2: ./hg status -R $REPO --config=experimental.dirstate-tree.in-memory=1
Time (mean ± σ): 1.291 s ± 0.008 s [User: 853.4 ms, System: 431.1 ms]
Range (min … max): 1.283 s … 1.309 s 10 runs
Summary
'./hg status -R $REPO --config=experimental.dirstate-tree.in-memory=1' ran
1.04 ± 0.02 times faster than '../hg2/hg status -R $REPO --config=experimental.dirstate-tree.in-memory=1'
```
* ./hg is this revision
* ../hg2/hg is its parent
* $REPO is an old snapshot of mozilla-central
Differential Revision: https://phab.mercurial-scm.org/D10550
from __future__ import absolute_import, print_function
import os
import sys
from mercurial import dispatch
def printb(data, end=b'\n'):
out = getattr(sys.stdout, 'buffer', sys.stdout)
out.write(data + end)
out.flush()
def testdispatch(cmd):
"""Simple wrapper around dispatch.dispatch()
Prints command and result value, but does not handle quoting.
"""
printb(b"running: %s" % (cmd,))
req = dispatch.request(cmd.split())
result = dispatch.dispatch(req)
printb(b"result: %r" % (result,))
testdispatch(b"init test1")
os.chdir('test1')
# create file 'foo', add and commit
f = open('foo', 'wb')
f.write(b'foo\n')
f.close()
testdispatch(b"add foo")
testdispatch(b"commit -m commit1 -d 2000-01-01 foo")
# append to file 'foo' and commit
f = open('foo', 'ab')
f.write(b'bar\n')
f.close()
testdispatch(b"commit -m commit2 -d 2000-01-02 foo")
# check 88803a69b24 (fancyopts modified command table)
testdispatch(b"log -r 0")
testdispatch(b"log -r tip")