Mercurial > hg
comparison mercurial/localrepo.py @ 39506:b66ea3fc3a86
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
| author | Boris Feld <boris.feld@octobus.net> |
|---|---|
| date | Fri, 07 Sep 2018 11:18:45 -0400 |
| parents | 9198e41df6ef |
| children | 41aa5dced975 |
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| 39505:c6b8eab5db19 | 39506:b66ea3fc3a86 |
|---|---|
| 68 interfaceutil, | 68 interfaceutil, |
| 69 procutil, | 69 procutil, |
| 70 stringutil, | 70 stringutil, |
| 71 ) | 71 ) |
| 72 | 72 |
| 73 from .revlogutils import ( | |
| 74 constants as revlogconst, | |
| 75 ) | |
| 76 | |
| 73 release = lockmod.release | 77 release = lockmod.release |
| 74 urlerr = util.urlerr | 78 urlerr = util.urlerr |
| 75 urlreq = util.urlreq | 79 urlreq = util.urlreq |
| 76 | 80 |
| 77 # set of (path, vfs-location) tuples. vfs-location is: | 81 # set of (path, vfs-location) tuples. vfs-location is: |
| 656 if r in self.openerreqs) | 660 if r in self.openerreqs) |
| 657 # experimental config: format.chunkcachesize | 661 # experimental config: format.chunkcachesize |
| 658 chunkcachesize = self.ui.configint('format', 'chunkcachesize') | 662 chunkcachesize = self.ui.configint('format', 'chunkcachesize') |
| 659 if chunkcachesize is not None: | 663 if chunkcachesize is not None: |
| 660 self.svfs.options['chunkcachesize'] = chunkcachesize | 664 self.svfs.options['chunkcachesize'] = chunkcachesize |
| 661 # experimental config: format.maxchainlen | |
| 662 maxchainlen = self.ui.configint('format', 'maxchainlen') | |
| 663 if maxchainlen is not None: | |
| 664 self.svfs.options['maxchainlen'] = maxchainlen | |
| 665 # experimental config: format.manifestcachesize | 665 # experimental config: format.manifestcachesize |
| 666 manifestcachesize = self.ui.configint('format', 'manifestcachesize') | 666 manifestcachesize = self.ui.configint('format', 'manifestcachesize') |
| 667 if manifestcachesize is not None: | 667 if manifestcachesize is not None: |
| 668 self.svfs.options['manifestcachesize'] = manifestcachesize | 668 self.svfs.options['manifestcachesize'] = manifestcachesize |
| 669 deltabothparents = self.ui.configbool('storage', | 669 deltabothparents = self.ui.configbool('storage', |
| 687 self.svfs.options['sparse-read-min-gap-size'] = srmingapsize | 687 self.svfs.options['sparse-read-min-gap-size'] = srmingapsize |
| 688 sparserevlog = SPARSEREVLOG_REQUIREMENT in self.requirements | 688 sparserevlog = SPARSEREVLOG_REQUIREMENT in self.requirements |
| 689 self.svfs.options['sparse-revlog'] = sparserevlog | 689 self.svfs.options['sparse-revlog'] = sparserevlog |
| 690 if sparserevlog: | 690 if sparserevlog: |
| 691 self.svfs.options['generaldelta'] = True | 691 self.svfs.options['generaldelta'] = True |
| 692 maxchainlen = None | |
| 693 if sparserevlog: | |
| 694 maxchainlen = revlogconst.SPARSE_REVLOG_MAX_CHAIN_LENGTH | |
| 695 # experimental config: format.maxchainlen | |
| 696 maxchainlen = self.ui.configint('format', 'maxchainlen', maxchainlen) | |
| 697 if maxchainlen is not None: | |
| 698 self.svfs.options['maxchainlen'] = maxchainlen | |
| 692 | 699 |
| 693 for r in self.requirements: | 700 for r in self.requirements: |
| 694 if r.startswith('exp-compression-'): | 701 if r.startswith('exp-compression-'): |
| 695 self.svfs.options['compengine'] = r[len('exp-compression-'):] | 702 self.svfs.options['compengine'] = r[len('exp-compression-'):] |
| 696 | 703 |