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
==========================================================
Test file dedicated to checking side-data related behavior
==========================================================
Check data can be written/read from sidedata
============================================
$ cat << EOF >> $HGRCPATH
> [extensions]
> testsidedata=$TESTDIR/testlib/ext-sidedata.py
> EOF
$ hg init test-sidedata --config format.exp-use-side-data=yes
$ cd test-sidedata
$ echo aaa > a
$ hg add a
$ hg commit -m a --traceback
$ echo aaa > b
$ hg add b
$ hg commit -m b
$ echo xxx >> a
$ hg commit -m aa
$ hg debugsidedata -c 0
2 sidedata entries
entry-0001 size 4
entry-0002 size 32
$ hg debugsidedata -c 1 -v
2 sidedata entries
entry-0001 size 4
'\x00\x00\x006'
entry-0002 size 32
'\x98\t\xf9\xc4v\xf0\xc5P\x90\xf7wRf\xe8\xe27e\xfc\xc1\x93\xa4\x96\xd0\x1d\x97\xaaG\x1d\xd7t\xfa\xde'
$ hg debugsidedata -m 2
2 sidedata entries
entry-0001 size 4
entry-0002 size 32
$ hg debugsidedata a 1
2 sidedata entries
entry-0001 size 4
entry-0002 size 32
Check upgrade behavior
======================
Right now, sidedata has not upgrade support
Check that we can upgrade to sidedata
-------------------------------------
$ hg init up-no-side-data --config format.exp-use-side-data=no
$ hg debugformat -v -R up-no-side-data
format-variant repo config default
fncache: yes yes yes
dotencode: yes yes yes
generaldelta: yes yes yes
sparserevlog: yes yes yes
sidedata: no no no
copies-sdc: no no no
plain-cl-delta: yes yes yes
compression: zlib zlib zlib
compression-level: default default default
$ hg debugformat -v -R up-no-side-data --config format.exp-use-side-data=yes
format-variant repo config default
fncache: yes yes yes
dotencode: yes yes yes
generaldelta: yes yes yes
sparserevlog: yes yes yes
sidedata: no yes no
copies-sdc: no no no
plain-cl-delta: yes yes yes
compression: zlib zlib zlib
compression-level: default default default
$ hg debugupgraderepo -R up-no-side-data --config format.exp-use-side-data=yes > /dev/null
Check that we can downgrade from sidedata
-----------------------------------------
$ hg init up-side-data --config format.exp-use-side-data=yes
$ hg debugformat -v -R up-side-data
format-variant repo config default
fncache: yes yes yes
dotencode: yes yes yes
generaldelta: yes yes yes
sparserevlog: yes yes yes
sidedata: yes no no
copies-sdc: no no no
plain-cl-delta: yes yes yes
compression: zlib zlib zlib
compression-level: default default default
$ hg debugformat -v -R up-side-data --config format.exp-use-side-data=no
format-variant repo config default
fncache: yes yes yes
dotencode: yes yes yes
generaldelta: yes yes yes
sparserevlog: yes yes yes
sidedata: yes no no
copies-sdc: no no no
plain-cl-delta: yes yes yes
compression: zlib zlib zlib
compression-level: default default default
$ hg debugupgraderepo -R up-side-data --config format.exp-use-side-data=no > /dev/null