spectral <spectral@google.com> [Thu, 16 Aug 2018 12:31:52 -0700] rev 39515
treemanifest: introduce lazy loading of subdirs
An earlier patch series made it so that what to load was up to the calling code,
which works fine until manifests are copied - when they're copied, they're
loaded completely and thus we lose the entire benefit.
By lazy loading everything, we can avoid having to pass in the matcher to ~every
manifest function, and handle copies correctly as well. This changeset doesn't
go as far as it could with loading only the necessary subsets, that will happen
in later changes in this series; at the moment, except in a few situations, we
just load everything the moment we want to interact with treemanifest._dirs.
This is thus most likely to be a small slowdown if treemanifests is in use
regardless of whether narrow is in use, but hopefully easier to verify
correctness and review.
This is part of a series of speedups, it is not expected to produce any real speed
improvements itself, but the numbers show that it doesn't produce a large speed
penalty in any common case, and for the cases it does provide a penalty in, it
is not a large absolute amount (even if it is a large percentage amount).
Timing numbers according to command:
hyperfine --prepare <preparation_script> 'hg status'
HGRCPATH points to a file with the following contents:
[extensions]
narrow =
strip =
rebase =
mozilla-unified (called m-u below) was at revision #468856.
regular hash: eb39298e432d
treemanifests hash: 0553b7f29eaf
large-dir-repo (called l-d-r below) was generated with the following script:
#!/bin/bash
hg init large-dir-repo
mkdir -p large-dir-repo/third_party/rust/log
touch large-dir-repo/third_party/rust/log/foo.txt
for i in $(seq 1 30000); do
d=$(mktemp -d large-dir-repo/third_party/XXXXXXXXX)
touch $d/file.txt
done
hg -R large-dir-repo ci -Am 'rev0' --user test --date '0 0'
echo hi > large-dir-repo/third_party/rust/log/bar.txt
hg -R large-dir-repo ci -Am 'rev1' --user test --date '0 0'
echo hi > large-dir-repo/third_party/rust/log/baz.txt
hg -R large-dir-repo ci -Am 'rev2' --user test --date '0 0'
for the repos that use narrow, the narrowspec was this:
[include]
rootfilesin:accessible/jsat
rootfilesin:accessible/tests/mochitest/jsat
rootfilesin:mobile/android/chrome/content
rootfilesin:mobile/android/modules/geckoview
rootfilesin:third_party/rust/log
[exclude]
This narrowspec was chosen due to the size of the third_party/rust directory
(this directory was *not* modified in revision #468856 in mozilla-unified),
plus all the directories that *were* modified in revision #468856 of
mozilla-unified.
Importantly, when using narrow, these repos had everything checked out (in the
case of large-dir-repo, that means all 30,001 directories), *before* adding the
narrowspec. This is to simulate the behavior when using a virtual filesystem
that shows everything for the user even if they haven't added it to the
narrowspec yet. This is not a supported configuration, and `hg update` and `hg
rebase` will not really do the "correct" thing if there are mutations outside
of the narrowspec (which is not the case in these tests, due to a carefully
crafted narrowspec), but non-mutating commands should behave correctly.
I'm not claiming anything less than a 5% speed win as improvements due to this
change; these are probably eiter measurement artifacts or constant time
improvements. The numbers that aren't changing are shown primarily to prove that
this doesn't make anything worse in any case I plan on testing during this
series.
'before' is hg from commit 6268fed3
'N' indicates narrow in use
'T' indicates treemanifest in use
Please note that these commands and the narrowspec are a little different than
the ones in a similar table that I made in a3cabe9415e1.
Important: it is my understanding that these numbers below are *not super reliable*,
the large slowdowns may be artifacts of some odd interaction between GC and
python module/code complexity. Another changeset of mine (D4351) had shown large
timing differences when ~empty, uncalled functions were added to match.py,
though only when using --color=never or redirecting to /dev/null. We seem to be
on some cusp of complexity or code size that is causing, at my best guess
(according to linux `perf` benchmarks) GC to alter behavior and cause a
200-400ms difference in timings. I haven't had a chance to replicate these
results on another machine.
diff --git:
repo | N | T | before (mean +- stdev) | after (mean +- stdev) | % of before
------+---+---+------------------------+-----------------------+------------
m-u | | | 1.580 s +- 0.034 s | 1.576 s +- 0.022 s | 99.7%
m-u | | x | 1.568 s +- 0.025 s | 1.584 s +- 0.044 s | 101.0%
m-u | x | | 1.569 s +- 0.031 s | 1.554 s +- 0.025 s | 99.0%
m-u | x | x | 107.3 ms +- 1.6 ms | 106.3 ms +- 1.5 ms | 99.1%
l-d-r | | | 232.5 ms +- 5.9 ms | 233.5 ms +- 5.3 ms | 100.4%
l-d-r | | x | 236.6 ms +- 6.3 ms | 233.6 ms +- 7.0 ms | 98.7%
l-d-r | x | | 118.4 ms +- 2.1 ms | 118.4 ms +- 1.4 ms | 100.0%
l-d-r | x | x | 116.8 ms +- 1.5 ms | 118.9 ms +- 1.6 ms | 101.8%
diff -c . --git:
repo | N | T | before (mean +- stdev) | after (mean +- stdev) | % of before
------+---+---+------------------------+-----------------------+------------
m-u | | | 354.4 ms +- 16.6 ms | 351.0 ms +- 6.9 ms | 99.0%
m-u | | x | 207.2 ms +- 3.0 ms | 206.2 ms +- 2.7 ms | 99.5%
m-u | x | | 422.0 ms +- 26.0 ms | 351.2 ms +- 6.4 ms | 83.2% <--
m-u | x | x | 166.7 ms +- 2.1 ms | 169.5 ms +- 4.1 ms | 101.7%
l-d-r | | | 98.4 ms +- 4.5 ms | 98.5 ms +- 2.1 ms | 100.1%
l-d-r | | x | 5.519 s +- 0.060 s | 5.149 s +- 0.042 s | 93.3% <--
l-d-r | x | | 99.1 ms +- 3.2 ms | 102.6 ms +- 9.7 ms | 103.5% <--?
l-d-r | x | x | 994.9 ms +- 10.7 ms | 1.026 s +- 0.012 s | 103.1% <--?
rebase -r . --keep -d .^^:
repo | N | T | before (mean +- stdev) | after (mean +- stdev) | % of before
------+---+---+------------------------+-----------------------+------------
m-u | | | 6.639 s +- 0.168 s | 6.559 s +- 0.097 s | 98.8%
m-u | | x | 6.601 s +- 0.143 s | 6.640 s +- 0.207 s | 100.6%
m-u | x | | 6.582 s +- 0.098 s | 6.543 s +- 0.098 s | 99.4%
m-u | x | x | 678.4 ms +- 57.7 ms | 703.7 ms +- 52.4 ms | 103.7% <--?
l-d-r | | | 780.0 ms +- 23.9 ms | 776.0 ms +- 12.6 ms | 99.5%
l-d-r | | x | 7.520 s +- 0.255 s | 7.395 s +- 0.044 s | 98.3%
l-d-r | x | | 331.9 ms +- 16.5 ms | 327.0 ms +- 3.4 ms | 98.5%
l-d-r | x | x | 6.228 s +- 0.113 s | 5.924 s +- 0.044 s | 95.1%
status --change . --copies:
repo | N | T | before (mean +- stdev) | after (mean +- stdev) | % of before
------+---+---+------------------------+-----------------------+------------
m-u | | | 330.8 ms +- 7.2 ms | 329.0 ms +- 7.1 ms | 99.5%
m-u | | x | 182.9 ms +- 2.7 ms | 183.5 ms +- 2.7 ms | 100.3%
m-u | x | | 330.0 ms +- 7.6 ms | 327.1 ms +- 5.4 ms | 99.1%
m-u | x | x | 146.2 ms +- 2.4 ms | 147.1 ms +- 1.3 ms | 100.6%
l-d-r | | | 95.3 ms +- 1.4 ms | 95.9 ms +- 1.5 ms | 100.6%
l-d-r | | x | 5.157 s +- 0.035 s | 5.166 s +- 0.058 s | 100.2%
l-d-r | x | | 99.7 ms +- 3.0 ms | 100.2 ms +- 4.4 ms | 100.5%
l-d-r | x | x | 993.6 ms +- 13.1 ms | 1.025 s +- 0.015 s | 103.2% <--?
status --copies:
repo | N | T | before (mean +- stdev) | after (mean +- stdev) | % of before
------+---+---+------------------------+-----------------------+------------
m-u | | | 2.348 s +- 0.031 s | 2.329 s +- 0.019 s | 99.2%
m-u | | x | 2.337 s +- 0.026 s | 2.346 s +- 0.034 s | 100.4%
m-u | x | | 2.354 s +- 0.015 s | 2.342 s +- 0.021 s | 99.5%
m-u | x | x | 120.6 ms +- 4.3 ms | 119.2 ms +- 2.1 ms | 98.8%
l-d-r | | | 731.5 ms +- 11.1 ms | 719.6 ms +- 9.8 ms | 98.4%
l-d-r | | x | 729.0 ms +- 15.5 ms | 725.7 ms +- 10.6 ms | 99.5%
l-d-r | x | | 211.0 ms +- 3.9 ms | 212.8 ms +- 3.7 ms | 100.9%
l-d-r | x | x | 211.5 ms +- 4.2 ms | 211.0 ms +- 3.3 ms | 99.8%
update $rev^; ~/src/hg/hg{hg}/hg update $rev:
repo | N | T | before (mean +- stdev) | after (mean +- stdev) | % of before
------+---+---+------------------------+-----------------------+------------
m-u | | | 3.910 s +- 0.055 s | 3.920 s +- 0.075 s | 100.3%
m-u | | x | 3.613 s +- 0.056 s | 3.630 s +- 0.056 s | 100.5%
m-u | x | | 3.873 s +- 0.055 s | 3.864 s +- 0.049 s | 99.8%
m-u | x | x | 400.4 ms +- 7.4 ms | 403.6 ms +- 5.0 ms | 100.8%
l-d-r | | | 531.6 ms +- 10.0 ms | 528.8 ms +- 9.6 ms | 99.5%
l-d-r | | x | 10.377 s +- 0.049 s | 9.955 s +- 0.046 s | 95.9%
l-d-r | x | | 308.3 ms +- 4.4 ms | 306.8 ms +- 3.7 ms | 99.5%
l-d-r | x | x | 1.805 s +- 0.015 s | 1.834 s +- 0.020 s | 101.6%
Differential Revision: https://phab.mercurial-scm.org/D4366
Boris Feld <boris.feld@octobus.net> [Fri, 07 Sep 2018 17:54:55 -0400] rev 39514
contrib: use a monotonic timer in catapipe
As spotted by Gregory, we should use a monotonic timer to get better timings.
Differential Revision: https://phab.mercurial-scm.org/D4516
Boris Feld <boris.feld@octobus.net> [Fri, 07 Sep 2018 17:51:07 -0400] rev 39513
contrib: fix catapipe output argument documentation
Differential Revision: https://phab.mercurial-scm.org/D4515
Boris Feld <boris.feld@octobus.net> [Thu, 06 Sep 2018 16:59:25 -0400] rev 39512
tracing: trace command function execution
Differential Revision: https://phab.mercurial-scm.org/D4514
Boris Feld <boris.feld@octobus.net> [Fri, 07 Sep 2018 16:51:51 -0400] rev 39511
extension: add a summary of total loading time per extension
Differential Revision: https://phab.mercurial-scm.org/D4513
Boris Feld <boris.feld@octobus.net> [Thu, 06 Sep 2018 16:49:37 -0400] rev 39510
extensions: trace the total time of running all reposetup callbacks
Differential Revision: https://phab.mercurial-scm.org/D4512
Boris Feld <boris.feld@octobus.net> [Thu, 06 Sep 2018 16:21:42 -0400] rev 39509
extensions: trace the total time of running all extsetup callbacks
Differential Revision: https://phab.mercurial-scm.org/D4511
Boris Feld <boris.feld@octobus.net> [Thu, 06 Sep 2018 16:20:05 -0400] rev 39508
extensions: trace the total time of running all uisetup callbacks
Differential Revision: https://phab.mercurial-scm.org/D4510
Boris Feld <boris.feld@octobus.net> [Mon, 10 Sep 2018 19:36:25 -0700] rev 39507
extensions: add timing for extensions reposetup
Differential Revision: https://phab.mercurial-scm.org/D4509
Boris Feld <boris.feld@octobus.net> [Fri, 07 Sep 2018 11:18:45 -0400] rev 39506
sparse-revlog: set max delta chain length to on thousand
The new snapshot system used in the sparse-revlog case gave us some small size
benefit so far. However its most important property is to gracefully handle
harder limit on delta chainlength.
Long delta chain has a very detrimental impact on read (and write) performance
in revlog. Being able to shorter them provide a great boost. However, shorting
delta used to result significantly lower compression ratio. The intermediate
snapshots effectively suppress most of this effect (even all in some case).
# Effect on the test repository
The repository we use for test is not "realistic" but can still show this in
action using an unreasonably low chain limit. Limiting the chain length show a
sizeable increase but stay under control: +6% for limit=15; +15% for limit=10.
Without the snapshot system the increase is significantly bigger: +45% for
limit=15; +80% for limit=10. Even slightly larger than without delta chain
limit, the resulting size is still smaller than before we started doing
snapshots.
Here is a table for comparison. *Since the repository is not branchy, the
initial sparse-revlog version does not bring much benefit compare to the
non-sparse one):
chain length limit | none | limit=15 | limit=10 |
without sparse-revlog | 62 818 987 | 112 664 615 | 131 222 574 |
without snapshot | 74 365 490 | 108 211 410 | 133 857 764 |
with snapshot | 59 230 936 | 63 002 924 | 68 415 329 |
# Effect On Real Life Repositories
The series provides significant benefits on all kind of repositories.
Using `hg debugupgraderepo -o redeltaparent --run`, we recomputed delta chain
for various repositories with different settings:
- delta chain length: unlimited or 1000 limit
- sparse-revlog: enabled or disabled
- this series: applied or not applied
We can observe multiple types of effect:
- On very branchy repositories:
* The delta chain limit as low impact on the repo size.
* Intermediate snapshot greatly reduces manifest size:
- pypy: -80%
- netbeans: -95%
* The delta chain limit is effective, without a size impact:
- netbeans average: 613 -> 282
- private #1 average: 1 068 -> 307
- On more linear repository:
* Intermediate snapshot limit the impact of delta chain limit:
- mozilla:
without the series: +360%
with the series: +25%
* The delta chain limit provides large improvement:
- mozilla's average chain length:
unlimited: 15 338
limited: 469
* Despite the chain length limit, the manifest size is reduced:
- mercurial: -25%
- mozilla: -30%
It is clear that the use of chains of intermediate snapshots provide large
benefits both in storage size and delta chains quality. We should now switch our
effort toward making sure the write performance are acceptable. Then,
`sparse-revlog` will be a suitable format for all new repository.
# Raw Statistic
* no-sparse: general delta repository not using sparse-revlog
* no-snapshot: sparse-revlog repository not using this series
* snapshot: sparse-revlog repository using this series
mercurial
Manifest Size:
limit | none | 1000
------------|-------------|------------
no-sparse | 8 021 373 | 8 199 366
no-snapshot | 8 103 561 | 8 259 719
snapshot | 6 137 116 | 6 126 433
Manifest Chain length data
limit || none || 1000 ||
value || average | max || average | max ||
------------||---------|---------||---------|---------||
no-sparse || 307 | 1456 || 279 | 1000 ||
no-snapshot || 312 | 1456 || 283 | 1000 ||
snapshot || 248 | 1208 || 241 | 1000 ||
Full Store Size
limit | none | 1000
------------|-------------|------------
no-sparse | 51 013 198 | 51 201 574
no-snapshot | 50 930 795 | 51 141 006
snapshot | 48 072 037 | 48 093 572
pypy
Manifest Size:
limit | none | 1000
------------|-------------|------------
no-sparse | 193 987 784 | 193 987 784
no-snapshot | 163 171 745 | 163 312 229
snapshot | 34 605 900 | 34 600 750
Manifest Chain length data
limit || none || 1000 ||
value || average | max || average | max ||
------------||---------|---------||---------|---------||
no-sparse || 101 | 692 || 101 | 692 ||
no-snapshot || 151 | 1307 || 148 | 1000 ||
snapshot || 128 | 1309 || 125 | 1000 ||
Full Store Size
limit | none | 1000
------------|-------------|------------
no-sparse | 495 931 473 | 495 931 473
no-snapshot | 465 441 017 | 465 581 501
snapshot | 355 467 301 | 355 472 451
Mozilla
Manifest Size:
limit | none | 1000
------------|----------------|---------------
no-sparse | 416 757 148 | 1 869 009 668
no-snapshot | 401 592 370 | 1 843 493 795
snapshot | 224 359 521 | 284 615 500
Manifest Chain length data
limit || none || 1000 ||
value || average | max || average | max ||
------------||---------|---------||---------|---------||
no-sparse || 15 333 | 58 980 || 468 | 1 000 ||
no-snapshot || 15 336 | 58 980 || 469 | 1 000 ||
snapshot || 15 338 | 58 983 || 469 | 1 000 ||
Full Store Size
limit | none | 1000
------------|----------------|---------------
no-sparse | 2 712 477 887 | 4 164 995 451
no-snapshot | 2 698 887 835 | 4 141 054 304
snapshot | 2 518 130 385 | 2 578 587 596
Netbeans
Manifest Size:
limit | none | 1000
------------|----------------|---------------
no-sparse | 4 766 794 101 | 4 870 642 687
no-snapshot | 4 334 806 082 | 4 428 681 309
snapshot | 232 659 666 | 240 330 665
Manifest Chain length data
limit || none || 1000 ||
value || average | max || average | max ||
------------||---------|---------||---------|---------||
no-sparse || 597 | 6802 || 254 | 1 000 ||
no-snapshot || 648 | 6 802 || 305 | 1 000 ||
snapshot || 613 | 6 804 || 282 | 1 000 ||
Full Store Size
limit | none | 1000
------------|----------------|---------------
no-sparse | 5 807 347 998 | 5 911 196 584
no-snapshot | 5 375 398 602 | 5 469 273 829
snapshot | 1 282 519 928 | 1 290 190 927
Private repo #1
Manifest Size:
limit | none | 1000
------------|-----------------|---------------
no-sparse | 41 389 010 840 | 41 398 162 091
no-snapshot | 9 737 319 435 | 10 223 773 150
snapshot | 744 215 807 | 747 961 822
Manifest Chain length data
limit || none || 1000 ||
value || average | max || average | max ||
------------||---------|---------||---------|---------||
no-sparse || 245 | 8 885 || 81 | 1 000 ||
no-snapshot || 1 225 | 8 885 || 336 | 1 000 ||
snapshot || 1 068 | 7 909 || 307 | 1 000 ||
Full Store Size
limit | none | 1000
------------|----------------|---------------
no-sparse | 49 646 065 126 | 49 655 216 377
no-snapshot | 17 924 862 856 | 18 411 316 571
snapshot | 9 009 024 710 | 9 012 770 725
Private repo #2
We currently have less data available for that repository.
* Before is a sparse-revlog repository without this series
* After is a sparse-revlog repository with this series + 1000 chain limit
Manifest Size:
Before: 1 531 485 040 bytes
After: 1 091 422 451 bytes
Manifest Chain:
Before: 2 218 avg; 6 575 Max
After: 442 avg; 1 000 Max
Full Store Size
Before: 15 203 955 615
after: 8 207 180 693