store: implement fncache basic path encoding in C
(This is not yet enabled; it will be turned on in a followup patch.)
The path encoding performed by fncache is complex and (perhaps
surprisingly) slow enough to negatively affect the overall performance
of Mercurial.
For a short path (< 120 bytes), the Python code can be reduced to a fairly
tractable state machine that either determines that nothing needs to be
done in a single pass, or performs the encoding in a second pass.
For longer paths, we avoid the more complicated hashed encoding scheme
for now, and fall back to Python.
Raw performance: I measured in a repo containing 150,000 files in its tip
manifest, with a median path name length of 57 bytes, and 95th percentile
of 96 bytes.
In this repo, the Python code takes 3.1 seconds to encode all path
names, while the hybrid C-and-Python code (called from Python) takes
0.21 seconds, for a speedup of about 14.
Across several other large repositories, I've measured the speedup from
the C code at between 26x and 40x.
For path names above 120 bytes where we must fall back to Python for
hashed encoding, the speedup is about 1.7x. Thus absolute performance
will depend strongly on the characteristics of a particular repository.
$ . "$TESTDIR/bzr-definitions"
empty directory
$ mkdir test-empty
$ cd test-empty
$ bzr init -q source
$ cd source
$ echo content > a
$ bzr add -q a
$ bzr commit -q -m 'Initial add'
$ mkdir empty
$ bzr add -q empty
$ bzr commit -q -m 'Empty directory added'
$ echo content > empty/something
$ bzr add -q empty/something
$ bzr commit -q -m 'Added file into directory'
$ cd ..
$ hg convert source source-hg
initializing destination source-hg repository
scanning source...
sorting...
converting...
2 Initial add
1 Empty directory added
0 Added file into directory
$ manifest source-hg 1
% manifest of 1
644 a
$ manifest source-hg tip
% manifest of tip
644 a
644 empty/something
$ cd ..
directory renames
$ mkdir test-dir-rename
$ cd test-dir-rename
$ bzr init -q source
$ cd source
$ mkdir tpyo
$ echo content > tpyo/something
$ bzr add -q tpyo
$ bzr commit -q -m 'Added directory'
$ bzr mv tpyo typo
tpyo => typo
$ bzr commit -q -m 'Oops, typo'
$ cd ..
$ hg convert source source-hg
initializing destination source-hg repository
scanning source...
sorting...
converting...
1 Added directory
0 Oops, typo
$ manifest source-hg 0
% manifest of 0
644 tpyo/something
$ manifest source-hg tip
% manifest of tip
644 typo/something
$ cd ..
nested directory renames
$ mkdir test-nested-dir-rename
$ cd test-nested-dir-rename
$ bzr init -q source
$ cd source
$ mkdir -p firstlevel/secondlevel/thirdlevel
$ echo content > firstlevel/secondlevel/file
$ echo this_needs_to_be_there_too > firstlevel/secondlevel/thirdlevel/stuff
$ bzr add -q firstlevel
$ bzr commit -q -m 'Added nested directories'
$ bzr mv firstlevel/secondlevel secondlevel
firstlevel/secondlevel => secondlevel
$ bzr commit -q -m 'Moved secondlevel one level up'
$ cd ..
$ hg convert source source-hg
initializing destination source-hg repository
scanning source...
sorting...
converting...
1 Added nested directories
0 Moved secondlevel one level up
$ manifest source-hg tip
% manifest of tip
644 secondlevel/file
644 secondlevel/thirdlevel/stuff
$ cd ..
directory remove
$ mkdir test-dir-remove
$ cd test-dir-remove
$ bzr init -q source
$ cd source
$ mkdir src
$ echo content > src/sourcecode
$ bzr add -q src
$ bzr commit -q -m 'Added directory'
$ bzr rm -q src
$ bzr commit -q -m 'Removed directory'
$ cd ..
$ hg convert source source-hg
initializing destination source-hg repository
scanning source...
sorting...
converting...
1 Added directory
0 Removed directory
$ manifest source-hg 0
% manifest of 0
644 src/sourcecode
$ manifest source-hg tip
% manifest of tip
$ cd ..
directory replace
$ mkdir test-dir-replace
$ cd test-dir-replace
$ bzr init -q source
$ cd source
$ mkdir first second
$ echo content > first/file
$ echo morecontent > first/dummy
$ echo othercontent > second/something
$ bzr add -q first second
$ bzr commit -q -m 'Initial layout'
$ bzr mv first/file second/file
first/file => second/file
$ bzr mv first third
first => third
$ bzr commit -q -m 'Some conflicting moves'
$ cd ..
$ hg convert source source-hg
initializing destination source-hg repository
scanning source...
sorting...
converting...
1 Initial layout
0 Some conflicting moves
$ manifest source-hg tip
% manifest of tip
644 second/file
644 second/something
644 third/dummy
$ cd ..
divergent nested renames (issue3089)
$ mkdir test-divergent-renames
$ cd test-divergent-renames
$ bzr init -q source
$ cd source
$ mkdir -p a/c
$ echo a > a/fa
$ echo c > a/c/fc
$ bzr add -q a
$ bzr commit -q -m 'Initial layout'
$ bzr mv a b
a => b
$ mkdir a
$ bzr add a
add(ed|ing) a (re)
$ bzr mv b/c a/c
b/c => a/c
$ bzr status
added:
a/
renamed:
a/? => b/? (re)
a/c/? => a/c/? (re)
$ bzr commit -q -m 'Divergent renames'
$ cd ..
$ hg convert source source-hg
initializing destination source-hg repository
scanning source...
sorting...
converting...
1 Initial layout
0 Divergent renames
$ hg -R source-hg st -C --change 1
A b/fa
a/fa
R a/fa
$ hg -R source-hg manifest -r 1
a/c/fc
b/fa
$ cd ..