annotate tests/test-convert-baz.t @ 48068:bf8837e3d7ce

dirstate: Remove the flat Rust DirstateMap implementation

Before this changeset we had two Rust implementations of `DirstateMap`.
This removes the "flat" DirstateMap so that the "tree" DirstateMap is always
used when Rust enabled. This simplifies the code a lot, and will enable
(in the next changeset) further removal of a trait abstraction.

This is a performance regression when:

* Rust is enabled, and
* The repository uses the legacy dirstate-v1 file format, and
* For `hg status`, unknown files are not listed (such as with `-mard`)

The regression is about 100 milliseconds for `hg status -mard` on a
semi-large repository (mozilla-central), from ~320ms to ~420ms.
We deem this to be small enough to be worth it.

The new dirstate-v2 is still experimental at this point, but we aim to
stabilize it (though not yet enable it by default for new repositories)
in Mercurial 6.0. Eventually, upgrating repositories to dirsate-v2 will
eliminate this regression (and enable other performance improvements).


# Background

The flat DirstateMap was introduced with the first Rust implementation of the
status algorithm. It works similarly to the previous Python + C one, with a
single `HashMap` that associates file paths to a `DirstateEntry` (where Python
has a dict).

We later added the tree DirstateMap where the root of the tree contains nodes
for files and directories that are directly at the root of the repository,
and nodes for directories can contain child nodes representing the files and
directly that *they* contain directly. The shape of this tree mirrors that of
the working directory in the filesystem. This enables the status algorithm to
traverse this tree in tandem with traversing the filesystem tree, which in
turns enables a more efficient algorithm.

Furthermore, the new dirstate-v2 file format is also based on a tree of the
same shape. The tree DirstateMap can access a dirstate-v2 file without parsing
it: binary data in a single large (possibly memory-mapped) bytes buffer is
traversed on demand. This allows `DirstateMap` creation to take `O(1)` time.
(Mutation works by creating new in-memory nodes with copy-on-write semantics,
and serialization is append-mostly.)

The tradeoff is that for "legacy" repositories that use the dirstate-v1 file
format, parsing that file into a tree DirstateMap takes more time. Profiling
shows that this time is dominated by `HashMap`. For a dirstate containing `F`
files with an average `D` directory depth, the flat DirstateMap does parsing
in `O(F)` number of HashMap operations but the tree DirstateMap in `O(F × D)`
operations, since each node has its own HashMap containing its child nodes.
This slower costs ~140ms on an old snapshot of mozilla-central, and ~80ms
on an old snapshot of the Netbeans repository.

The status algorithm is faster, but with `-mard` (when not listing unknown
files) it is typically not faster *enough* to compensate the slower parsing.

Both Rust implementations are always faster than the Python + C implementation


# Benchmark results

All benchmarks are run on changeset 98c0408324e6, with repositories that use
the dirstate-v1 file format, on a server with 4 CPU cores and 4 CPU threads
(no HyperThreading).

`hg status` benchmarks show wall clock times of the entire command as the
average and standard deviation of serveral runs, collected by
https://github.com/sharkdp/hyperfine and reformated.

Parsing benchmarks are wall clock time of the Rust function that converts a
bytes buffer of the dirstate file into the `DirstateMap` data structure as
used by the status algorithm. A single run each, collected by running
`hg status` this environment variable:

    RUST_LOG=hg::dirstate::dirstate_map=trace,hg::dirstate_tree::dirstate_map=trace


Benchmark 1: Rust flat DirstateMap → Rust tree DirstateMap

    hg status

    mozilla-clean    	562.3 ms ± 2.0 ms	→	462.5 ms ± 0.6 ms	 1.22 ± 0.00 times faster
    mozilla-dirty    	859.6 ms ± 2.2 ms	→	719.5 ms ± 3.2 ms	 1.19 ± 0.01 times faster
    mozilla-ignored  	558.2 ms ± 3.0 ms	→	457.9 ms ± 2.9 ms	 1.22 ± 0.01 times faster
    mozilla-unknowns 	859.4 ms ± 5.7 ms	→	716.0 ms ± 4.7 ms	 1.20 ± 0.01 times faster
    netbeans-clean   	336.5 ms ± 0.9 ms	→	339.5 ms ± 0.4 ms	 0.99 ± 0.00 times faster
    netbeans-dirty   	491.4 ms ± 1.6 ms	→	475.1 ms ± 1.2 ms	 1.03 ± 0.00 times faster
    netbeans-ignored 	343.7 ms ± 1.0 ms	→	347.8 ms ± 0.4 ms	 0.99 ± 0.00 times faster
    netbeans-unknowns	484.3 ms ± 1.0 ms	→	466.0 ms ± 1.2 ms	 1.04 ± 0.00 times faster

    hg status -mard

    mozilla-clean    	317.3 ms ± 0.6 ms	→	422.5 ms ± 1.2 ms	 0.75 ± 0.00 times faster
    mozilla-dirty    	315.4 ms ± 0.6 ms	→	417.7 ms ± 1.1 ms	 0.76 ± 0.00 times faster
    mozilla-ignored  	314.6 ms ± 0.6 ms	→	417.4 ms ± 1.0 ms	 0.75 ± 0.00 times faster
    mozilla-unknowns 	312.9 ms ± 0.9 ms	→	417.3 ms ± 1.6 ms	 0.75 ± 0.00 times faster
    netbeans-clean   	212.0 ms ± 0.6 ms	→	283.6 ms ± 0.8 ms	 0.75 ± 0.00 times faster
    netbeans-dirty   	211.4 ms ± 1.0 ms	→	283.4 ms ± 1.6 ms	 0.75 ± 0.01 times faster
    netbeans-ignored 	211.4 ms ± 0.9 ms	→	283.9 ms ± 0.8 ms	 0.74 ± 0.01 times faster
    netbeans-unknowns	211.1 ms ± 0.6 ms	→	283.4 ms ± 1.0 ms	 0.74 ± 0.00 times faster

    Parsing

    mozilla-clean       38.4ms → 177.6ms
    mozilla-dirty       38.8ms → 177.0ms
    mozilla-ignored     38.8ms → 178.0ms
    mozilla-unknowns    38.7ms → 176.9ms
    netbeans-clean      16.5ms → 97.3ms
    netbeans-dirty      16.5ms → 98.4ms
    netbeans-ignored    16.9ms → 97.4ms
    netbeans-unknowns   16.9ms → 96.3ms


Benchmark 2: Python + C dirstatemap → Rust tree DirstateMap

    hg status

    mozilla-clean    	1261.0 ms ± 3.6 ms	→	461.1 ms ± 0.5 ms	 2.73 ± 0.00 times faster
    mozilla-dirty    	2293.4 ms ± 9.1 ms	→	719.6 ms ± 3.6 ms	 3.19 ± 0.01 times faster
    mozilla-ignored  	1240.4 ms ± 2.3 ms	→	457.7 ms ± 1.9 ms	 2.71 ± 0.00 times faster
    mozilla-unknowns 	2283.3 ms ± 9.0 ms	→	719.7 ms ± 3.8 ms	 3.17 ± 0.01 times faster
    netbeans-clean   	879.7 ms ± 3.5 ms	→	339.9 ms ± 0.5 ms	 2.59 ± 0.00 times faster
    netbeans-dirty   	1257.3 ms ± 4.7 ms	→	474.6 ms ± 1.6 ms	 2.65 ± 0.01 times faster
    netbeans-ignored 	943.9 ms ± 1.9 ms	→	347.3 ms ± 1.1 ms	 2.72 ± 0.00 times faster
    netbeans-unknowns	1188.1 ms ± 5.0 ms	→	465.2 ms ± 2.3 ms	 2.55 ± 0.01 times faster

    hg status -mard

    mozilla-clean    	903.2 ms ± 3.6 ms	→	423.4 ms ± 2.2 ms	 2.13 ± 0.01 times faster
    mozilla-dirty    	884.6 ms ± 4.5 ms	→	417.3 ms ± 1.4 ms	 2.12 ± 0.01 times faster
    mozilla-ignored  	881.9 ms ± 1.3 ms	→	417.3 ms ± 0.8 ms	 2.11 ± 0.00 times faster
    mozilla-unknowns 	878.5 ms ± 1.9 ms	→	416.4 ms ± 0.9 ms	 2.11 ± 0.00 times faster
    netbeans-clean   	434.9 ms ± 1.8 ms	→	284.0 ms ± 0.8 ms	 1.53 ± 0.01 times faster
    netbeans-dirty   	434.1 ms ± 0.8 ms	→	283.1 ms ± 0.8 ms	 1.53 ± 0.00 times faster
    netbeans-ignored 	431.7 ms ± 1.1 ms	→	283.6 ms ± 1.8 ms	 1.52 ± 0.01 times faster
    netbeans-unknowns	433.0 ms ± 1.3 ms	→	283.5 ms ± 0.7 ms	 1.53 ± 0.00 times faster

Differential Revision: https://phab.mercurial-scm.org/D11516

#require baz symlink

  $ baz my-id "mercurial <[e-mail]>"

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "convert=" >> $HGRCPATH

create baz archive
  $ baz make-archive baz@mercurial--convert hg-test-convert-baz

initialize baz repo
  $ mkdir baz-repo
  $ cd baz-repo/
  $ baz init-tree baz@mercurial--convert/baz--test--0
  $ baz import
  * creating version baz@mercurial--convert/baz--test--0
  * imported baz@mercurial--convert/baz--test--0

create initial files
  $ echo 'this is a file' > a
  $ baz add a
  $ mkdir src
  $ baz add src
  $ cd src
  $ dd count=1 if=/dev/zero of=b > /dev/null 2> /dev/null
  $ baz add b
HACK: hide GNU tar-1.22 "tar: The --preserve option is deprecated, use --preserve-permissions --preserve-order instead"
  $ baz commit -s "added a file, src and src/b (binary)" 2>&1 | grep -v '^tar'
  * build pristine tree for baz@mercurial--convert/baz--test--0--base-0
  * Scanning for full-tree revision: .
  * from import revision: baz@mercurial--convert/baz--test--0--base-0
  A/ .arch-ids
  A/ src
  A/ src/.arch-ids
  A  .arch-ids/a.id
  A  a
  A  src/.arch-ids/=id
  A  src/.arch-ids/b.id
  A  src/b
  * update pristine tree (baz@mercurial--convert/baz--test--0--base-0 => baz--test--0--patch-1)
  * committed baz@mercurial--convert/baz--test--0--patch-1

create link file and modify a
  $ ln -s ../a a-link
  $ baz add a-link
  $ echo 'this a modification to a' >> ../a
  $ baz commit -s "added link to a and modify a"
  A  src/.arch-ids/a-link.id
  A  src/a-link
  M  a
  * update pristine tree (baz@mercurial--convert/baz--test--0--patch-1 => baz--test--0--patch-2)
  * committed baz@mercurial--convert/baz--test--0--patch-2

create second link and modify b
  $ ln -s ../a a-link-2
  $ baz add a-link-2
  $ dd count=1 seek=1 if=/dev/zero of=b > /dev/null 2> /dev/null
  $ baz commit -s "added second link and modify b"
  A  src/.arch-ids/a-link-2.id
  A  src/a-link-2
  Mb src/b
  * update pristine tree (baz@mercurial--convert/baz--test--0--patch-2 => baz--test--0--patch-3)
  * committed baz@mercurial--convert/baz--test--0--patch-3

b file to link and a-link-2 to regular file
  $ rm -f a-link-2
  $ echo 'this is now a regular file' > a-link-2
  $ ln -sf ../a b
  $ baz commit -s "file to link and link to file test"
  fl src/b
  lf src/a-link-2
  * update pristine tree (baz@mercurial--convert/baz--test--0--patch-3 => baz--test--0--patch-4)
  * committed baz@mercurial--convert/baz--test--0--patch-4

move a-link-2 file and src directory
  $ cd ..
  $ baz mv src/a-link-2 c
  $ baz mv src test
  $ baz commit -s "move and rename a-link-2 file and src directory"
  D/ src/.arch-ids
  A/ test/.arch-ids
  /> src	test
  => src/.arch-ids/a-link-2.id	.arch-ids/c.id
  => src/a-link-2	c
  => src/.arch-ids/=id	test/.arch-ids/=id
  => src/.arch-ids/a-link.id	test/.arch-ids/a-link.id
  => src/.arch-ids/b.id	test/.arch-ids/b.id
  * update pristine tree (baz@mercurial--convert/baz--test--0--patch-4 => baz--test--0--patch-5)
  * committed baz@mercurial--convert/baz--test--0--patch-5

move and add the moved file again
  $ echo e > e
  $ baz add e
  $ baz commit -s "add e"
  A  .arch-ids/e.id
  A  e
  * update pristine tree (baz@mercurial--convert/baz--test--0--patch-5 => baz--test--0--patch-6)
  * committed baz@mercurial--convert/baz--test--0--patch-6
  $ baz mv e f
  $ echo ee > e
  $ baz add e
  $ baz commit -s "move e and recreate it again"
  A  .arch-ids/e.id
  A  e
  => .arch-ids/e.id	.arch-ids/f.id
  => e	f
  * update pristine tree (baz@mercurial--convert/baz--test--0--patch-6 => baz--test--0--patch-7)
  * committed baz@mercurial--convert/baz--test--0--patch-7
  $ cd ..

converting baz repo to Mercurial
  $ hg convert baz-repo baz-repo-hg
  initializing destination baz-repo-hg repository
  analyzing tree version baz@mercurial--convert/baz--test--0...
  scanning source...
  sorting...
  converting...
  7 initial import
  6 added a file, src and src/b (binary)
  5 added link to a and modify a
  4 added second link and modify b
  3 file to link and link to file test
  2 move and rename a-link-2 file and src directory
  1 add e
  0 move e and recreate it again

  $ baz register-archive -d baz@mercurial--convert

  $ glog()
  > {
  >     hg log -G --template '{rev} "{desc|firstline}" files: {files}\n' "$@"
  > }

show graph log
  $ glog -R baz-repo-hg
  o  7 "move e and recreate it again" files: e f
  |
  o  6 "add e" files: e
  |
  o  5 "move and rename a-link-2 file and src directory" files: c src/a-link src/a-link-2 src/b test/a-link test/b
  |
  o  4 "file to link and link to file test" files: src/a-link-2 src/b
  |
  o  3 "added second link and modify b" files: src/a-link-2 src/b
  |
  o  2 "added link to a and modify a" files: a src/a-link
  |
  o  1 "added a file, src and src/b (binary)" files: a src/b
  |
  o  0 "initial import" files:
  
  $ hg up -q -R baz-repo-hg
  $ hg -R baz-repo-hg manifest --debug
  c4072c4b72e1cabace081888efa148ee80ca3cbb 644   a
  0201ac32a3a8e86e303dff60366382a54b48a72e 644   c
  1a4a864db0073705a11b1439f563bfa4b46d9246 644   e
  09e0222742fc3f75777fa9d68a5d8af7294cb5e7 644   f
  c0067ba5ff0b7c9a3eb17270839d04614c435623 644 @ test/a-link
  375f4263d86feacdea7e3c27100abd1560f2a973 644 @ test/b
  $ hg -R baz-repo-hg log -r 5 -r 7 -C --debug | grep copies
  copies:      c (src/a-link-2) test/a-link (src/a-link) test/b (src/b)
  copies:      f (e)