nodemap: introduce an option to use mmap to read the nodemap mapping
The performance and memory benefit is much greater if we don't have to copy all
the data in memory for each information. So we introduce an option (on by
default) to read the data using mmap.
This changeset is the last one definition the API for index support nodemap
data. (they have to be able to use the mmaping).
Below are some benchmark comparing the best we currently have in 5.3 with the
final step of this series (using the persistent nodemap implementation in
Rust). The benchmark run `hg perfindex` with various revset and the following
variants:
Before:
* do not use the persistent nodemap
* use the CPython implementation of the index for nodemap
* use mmapping of the changelog index
After:
* use the MixedIndex Rust code, with the NodeTree object for nodemap access
(still in review)
* use the persistent nodemap data from disk
* access the persistent nodemap data through mmap
* use mmapping of the changelog index
The persistent nodemap greatly speed up most operation on very large
repositories. Some of the previously very fast lookup end up a bit slower because
the persistent nodemap has to be setup. However the absolute slowdown is very
small and won't matters in the big picture.
Here are some numbers (in seconds) for the reference copy of mozilla-try:
Revset Before After abs-change speedup
-10000: 0.004622 0.005532 0.000910 × 0.83
-10: 0.000050 0.000132 0.000082 × 0.37
tip 0.000052 0.000085 0.000033 × 0.61
0 + (-10000:) 0.028222 0.005337 -0.022885 × 5.29
0 0.023521 0.000084 -0.023437 × 280.01
(-10000:) + 0 0.235539 0.005308 -0.230231 × 44.37
(-10:) + :9 0.232883 0.000180 -0.232703 ×1293.79
(-10000:) + (:99) 0.238735 0.005358 -0.233377 × 44.55
:99 + (-10000:) 0.317942 0.005593 -0.312349 × 56.84
:9 + (-10:) 0.313372 0.000179 -0.313193 ×1750.68
:9 0.316450 0.000143 -0.316307 ×2212.93
On smaller repositories, the cost of nodemap related operation is not as big, so
the win is much more modest. Yet it helps shaving a handful of millisecond here
and there.
Here are some numbers (in seconds) for the reference copy of mercurial:
Revset Before After abs-change speedup
-10: 0.000065 0.000097 0.000032 × 0.67
tip 0.000063 0.000078 0.000015 × 0.80
0 0.000561 0.000079 -0.000482 × 7.10
-10000: 0.004609 0.003648 -0.000961 × 1.26
0 + (-10000:) 0.005023 0.003715 -0.001307 × 1.35
(-10:) + :9 0.002187 0.000108 -0.002079 ×20.25
(-10000:) + 0 0.006252 0.003716 -0.002536 × 1.68
(-10000:) + (:99) 0.006367 0.003707 -0.002660 × 1.71
:9 + (-10:) 0.003846 0.000110 -0.003736 ×34.96
:9 0.003854 0.000099 -0.003755 ×38.92
:99 + (-10000:) 0.007644 0.003778 -0.003866 × 2.02
Differential Revision: https://phab.mercurial-scm.org/D7894
$ cat >> $HGRCPATH <<EOF
> [extensions]
> convert=
> EOF
$ hg init t
$ cd t
$ echo a >> a
$ hg ci -Am a0 -d '1 0'
adding a
$ hg branch brancha
marked working directory as branch brancha
(branches are permanent and global, did you want a bookmark?)
$ echo a >> a
$ hg ci -m a1 -d '2 0'
$ echo a >> a
$ hg ci -m a2 -d '3 0'
$ echo a >> a
$ hg ci -m a3 -d '4 0'
$ hg up -C 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg branch branchb
marked working directory as branch branchb
$ echo b >> b
$ hg ci -Am b0 -d '6 0'
adding b
$ hg up -C brancha
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo a >> a
$ hg ci -m a4 -d '5 0'
$ echo a >> a
$ hg ci -m a5 -d '7 0'
$ echo a >> a
$ hg ci -m a6 -d '8 0'
$ hg up -C branchb
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo b >> b
$ hg ci -m b1 -d '9 0'
$ hg up -C 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo c >> c
$ hg branch branchc
marked working directory as branch branchc
$ hg ci -Am c0 -d '10 0'
adding c
$ hg up -C brancha
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg ci --close-branch -m a7x -d '11 0'
$ hg up -C branchb
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg ci --close-branch -m b2x -d '12 0'
$ hg up -C branchc
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg merge branchb
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -m c1 -d '13 0'
$ cd ..
convert with datesort
$ hg convert --datesort t t-datesort
initializing destination t-datesort repository
scanning source...
sorting...
converting...
12 a0
11 a1
10 a2
9 a3
8 a4
7 b0
6 a5
5 a6
4 b1
3 c0
2 a7x
1 b2x
0 c1
graph converted repo
$ hg -R t-datesort log -G --template '{rev} "{desc}"\n'
o 12 "c1"
|\
| _ 11 "b2x"
| |
| | _ 10 "a7x"
| | |
o | | 9 "c0"
| | |
| o | 8 "b1"
| | |
| | o 7 "a6"
| | |
| | o 6 "a5"
| | |
| o | 5 "b0"
|/ /
| o 4 "a4"
| |
| o 3 "a3"
| |
| o 2 "a2"
| |
| o 1 "a1"
|/
o 0 "a0"
convert with datesort (default mode)
$ hg convert t t-sourcesort
initializing destination t-sourcesort repository
scanning source...
sorting...
converting...
12 a0
11 a1
10 a2
9 a3
8 b0
7 a4
6 a5
5 a6
4 b1
3 c0
2 a7x
1 b2x
0 c1
graph converted repo
$ hg -R t-sourcesort log -G --template '{rev} "{desc}"\n'
o 12 "c1"
|\
| _ 11 "b2x"
| |
| | _ 10 "a7x"
| | |
o | | 9 "c0"
| | |
| o | 8 "b1"
| | |
| | o 7 "a6"
| | |
| | o 6 "a5"
| | |
| | o 5 "a4"
| | |
| o | 4 "b0"
|/ /
| o 3 "a3"
| |
| o 2 "a2"
| |
| o 1 "a1"
|/
o 0 "a0"
convert with closesort
$ hg convert --closesort t t-closesort
initializing destination t-closesort repository
scanning source...
sorting...
converting...
12 a0
11 a1
10 a2
9 a3
8 b0
7 a4
6 a5
5 a6
4 a7x
3 b1
2 b2x
1 c0
0 c1
graph converted repo
$ hg -R t-closesort log -G --template '{rev} "{desc}"\n'
o 12 "c1"
|\
| o 11 "c0"
| |
_ | 10 "b2x"
| |
o | 9 "b1"
| |
| | _ 8 "a7x"
| | |
| | o 7 "a6"
| | |
| | o 6 "a5"
| | |
| | o 5 "a4"
| | |
o | | 4 "b0"
|/ /
| o 3 "a3"
| |
| o 2 "a2"
| |
| o 1 "a1"
|/
o 0 "a0"