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
#require no-windows
$ . "$TESTDIR/remotefilelog-library.sh"
$ hg init master
$ cd master
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> server=True
> EOF
$ echo x > x
$ hg commit -qAm x
$ echo y > y
$ rm x
$ hg commit -qAm DxAy
$ echo yy > y
$ hg commit -qAm y
$ cd ..
$ hgcloneshallow ssh://user@dummy/master shallow -q
1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob)
# Set the prefetchdays config to zero so that all commits are prefetched
# no matter what their creation date is.
$ cd shallow
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> prefetchdays=0
> EOF
$ cd ..
# Prefetch all data and repack
$ cd shallow
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> bgprefetchrevs=all()
> EOF
$ hg prefetch
2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob)
$ hg repack
$ find $CACHEDIR | sort | egrep ".datapack|.histpack"
$TESTTMP/hgcache/master/packs/7bcd2d90b99395ca43172a0dd24e18860b2902f9.histpack
$TESTTMP/hgcache/master/packs/dc8f8fdc76690ce27791ce9f53a18da379e50d37.datapack
# Ensure that all file versions were prefetched
$ hg debugdatapack `ls -ct $TESTTMP/hgcache/master/packs/*.datapack | head -n 1`
$TESTTMP/hgcache/master/packs/dc8f8fdc76690ce27791ce9f53a18da379e50d37:
x:
Node Delta Base Delta Length Blob Size
1406e7411862 000000000000 2 2
Total: 2 2 (0.0% bigger)
y:
Node Delta Base Delta Length Blob Size
50dbc4572b8e 000000000000 3 3
076f5e2225b3 50dbc4572b8e 14 2
Total: 17 5 (240.0% bigger)
# Test garbage collection during repack
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> bgprefetchrevs=tip
> gcrepack=True
> nodettl=86400
> EOF
$ hg repack
$ find $CACHEDIR | sort | egrep ".datapack|.histpack"
$TESTTMP/hgcache/master/packs/7bcd2d90b99395ca43172a0dd24e18860b2902f9.histpack
$TESTTMP/hgcache/master/packs/a4e1d094ec2aee8a08a4d6d95a13c634cc7d7394.datapack
# Ensure that file 'x' was garbage collected. It should be GCed because it is not in the keepset
# and is old (commit date is 0.0 in tests). Ensure that file 'y' is present as it is in the keepset.
$ hg debugdatapack `ls -ct $TESTTMP/hgcache/master/packs/*.datapack | head -n 1`
$TESTTMP/hgcache/master/packs/a4e1d094ec2aee8a08a4d6d95a13c634cc7d7394:
y:
Node Delta Base Delta Length Blob Size
50dbc4572b8e 000000000000 3 3
Total: 3 3 (0.0% bigger)
# Prefetch all data again and repack for later garbage collection
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> bgprefetchrevs=all()
> EOF
$ hg prefetch
2 files fetched over 1 fetches - (2 misses, 0.00% hit ratio) over *s (glob)
$ hg repack
$ find $CACHEDIR | sort | egrep ".datapack|.histpack"
$TESTTMP/hgcache/master/packs/7bcd2d90b99395ca43172a0dd24e18860b2902f9.histpack
$TESTTMP/hgcache/master/packs/dc8f8fdc76690ce27791ce9f53a18da379e50d37.datapack
# Ensure that all file versions were prefetched
$ hg debugdatapack `ls -ct $TESTTMP/hgcache/master/packs/*.datapack | head -n 1`
$TESTTMP/hgcache/master/packs/dc8f8fdc76690ce27791ce9f53a18da379e50d37:
x:
Node Delta Base Delta Length Blob Size
1406e7411862 000000000000 2 2
Total: 2 2 (0.0% bigger)
y:
Node Delta Base Delta Length Blob Size
50dbc4572b8e 000000000000 3 3
076f5e2225b3 50dbc4572b8e 14 2
Total: 17 5 (240.0% bigger)
# Test garbage collection during repack. Ensure that new files are not removed even though they are not in the keepset
# For the purposes of the test the TTL of a file is set to current time + 100 seconds. i.e. all commits in tests have
# a date of 1970 and therefore to prevent garbage collection we have to set nodettl to be farther from 1970 than we are now.
$ cat >> .hg/hgrc <<EOF
> [remotefilelog]
> bgprefetchrevs=
> nodettl=$(($(date +%s) + 100))
> EOF
$ hg repack
$ find $CACHEDIR | sort | egrep ".datapack|.histpack"
$TESTTMP/hgcache/master/packs/7bcd2d90b99395ca43172a0dd24e18860b2902f9.histpack
$TESTTMP/hgcache/master/packs/dc8f8fdc76690ce27791ce9f53a18da379e50d37.datapack
# Ensure that all file versions were prefetched
$ hg debugdatapack `ls -ct $TESTTMP/hgcache/master/packs/*.datapack | head -n 1`
$TESTTMP/hgcache/master/packs/dc8f8fdc76690ce27791ce9f53a18da379e50d37:
x:
Node Delta Base Delta Length Blob Size
1406e7411862 000000000000 2 2
Total: 2 2 (0.0% bigger)
y:
Node Delta Base Delta Length Blob Size
50dbc4572b8e 000000000000 3 3
076f5e2225b3 50dbc4572b8e 14 2
Total: 17 5 (240.0% bigger)