phases: rework the logic of _pushdiscoveryphase to bound complexity
This rework the various graph traversal in _pushdiscoveryphase to keep the
complexity in check.
This is done though a couple of things:
- first, limiting the space we have to explore, for example, if we are not in
publishing push, we don't need to consider remote draft roots that are also
draft locally, as there is nothing to be moved there.
- avoid unbounded descendant computation, and use the faster "rev between"
computation.
This provide a massive boost to performance when exchanging with repository with
a massive amount of draft, like mozilla-try:
### data-env-vars.name = mozilla-try-2023-03-22-zstd-sparse-revlog
# benchmark.name = hg.command.push
# bin-env-vars.hg.flavor = default
# bin-env-vars.hg.py-re2-module = default
# benchmark.variants.explicit-rev = all-out-heads
# benchmark.variants.issue6528 = disabled
# benchmark.variants.protocol = ssh
# benchmark.variants.reuse-external-delta-parent = default
## benchmark.variants.revs = any-1-extra-rev
before: 20.346590 seconds
after: 11.232059 seconds (-38.15%, -7.48 seconds)
## benchmark.variants.revs = any-100-extra-rev
before: 24.752051 seconds
after: 15.367412 seconds (-37.91%, -9.38 seconds)
After this changes, the push operation is still quite too slow. Some of this
can be attributed to general phases slowness (reading all the roots from disk
for example) and other know slowness (not using persistent-nodemap, branchmap,
tags, etc. We are also working on them, but with this series, phase discovery
during push no longer showing up in profile and this is a pretty nice and bit
low-hanging fruit out of the way.
### (same case as the above)
# benchmark.variants.revs = any-1-extra-rev
pre-%ln-change: 44.235070
this-changeset: 11.232059 seconds (-74.61%, -33.00 seconds)
# benchmark.variants.revs = any-100-extra-rev
pre-%ln-change: 49.234697
this-changeset: 15.367412 seconds (-68.79%, -33.87 seconds)
Note that with this change, the `hg push` performance is now much closer to the
`hg pull` performance, even it still lagging behind a bit. (and the overall
performance are still too slow).
### data-env-vars.name = mozilla-try-2023-03-22-ds2-pnm
# benchmark.variants.explicit-rev = all-out-heads
# benchmark.variants.issue6528 = disabled
# benchmark.variants.protocol = ssh
# benchmark.variants.pulled-delta-reuse-policy = default
# bin-env-vars.hg.flavor = rust
## benchmark.variants.revs = any-1-extra-rev
hg.command.pull: 6.517450
hg.command.push: 11.219888
## benchmark.variants.revs = any-100-extra-rev
hg.command.pull: 10.160991
hg.command.push: 14.251107
### data-env-vars.name = mozilla-try-2023-03-22-zstd-sparse-revlog
# bin-env-vars.hg.py-re2-module = default
# benchmark.variants.explicit-rev = all-out-heads
# benchmark.variants.issue6528 = disabled
# benchmark.variants.protocol = ssh
# benchmark.variants.pulled-delta-reuse-policy = default
## bin-env-vars.hg.flavor = default
## benchmark.variants.revs = any-1-extra-rev
hg.command.pull: 8.577772
hg.command.push: 11.232059
## bin-env-vars.hg.flavor = default
## benchmark.variants.revs = any-100-extra-rev
hg.command.pull: 13.152976
hg.command.push: 15.367412
## bin-env-vars.hg.flavor = rust
## benchmark.variants.revs = any-1-extra-rev
hg.command.pull: 8.731982
hg.command.push: 11.178751
## bin-env-vars.hg.flavor = rust
## benchmark.variants.revs = any-100-extra-rev
hg.command.pull: 13.184236
hg.command.push: 15.620843
# This is a randomized test that generates different pathnames every
# time it is invoked, and tests the encoding of those pathnames.
#
# It uses a simple probabilistic model to generate valid pathnames
# that have proven likely to expose bugs and divergent behavior in
# different encoding implementations.
import binascii
import collections
import itertools
import math
import os
import random
import sys
import time
from mercurial import (
pycompat,
store,
)
validchars = set(map(pycompat.bytechr, range(0, 256)))
alphanum = range(ord('A'), ord('Z'))
for c in (b'\0', b'/'):
validchars.remove(c)
winreserved = (
b'aux con prn nul'.split()
+ [b'com%d' % i for i in range(1, 10)]
+ [b'lpt%d' % i for i in range(1, 10)]
)
def casecombinations(names):
'''Build all case-diddled combinations of names.'''
combos = set()
for r in names:
for i in range(len(r) + 1):
for c in itertools.combinations(range(len(r)), i):
d = r
for j in c:
d = b''.join((d[:j], d[j : j + 1].upper(), d[j + 1 :]))
combos.add(d)
return sorted(combos)
def buildprobtable(fp, cmd='hg manifest tip'):
"""Construct and print a table of probabilities for path name
components. The numbers are percentages."""
counts = collections.defaultdict(lambda: 0)
for line in os.popen(cmd).read().splitlines():
if line[-2:] in ('.i', '.d'):
line = line[:-2]
if line.startswith('data/'):
line = line[5:]
for c in line:
counts[c] += 1
for c in '\r/\n':
counts.pop(c, None)
t = sum(counts.values()) / 100.0
fp.write('probtable = (')
for i, (k, v) in enumerate(
sorted(counts.items(), key=lambda x: x[1], reverse=True)
):
if (i % 5) == 0:
fp.write('\n ')
vt = v / t
if vt < 0.0005:
break
fp.write('(%r, %.03f), ' % (k, vt))
fp.write('\n )\n')
# A table of character frequencies (as percentages), gleaned by
# looking at filelog names from a real-world, very large repo.
probtable = (
(b't', 9.828),
(b'e', 9.042),
(b's', 8.011),
(b'a', 6.801),
(b'i', 6.618),
(b'g', 5.053),
(b'r', 5.030),
(b'o', 4.887),
(b'p', 4.363),
(b'n', 4.258),
(b'l', 3.830),
(b'h', 3.693),
(b'_', 3.659),
(b'.', 3.377),
(b'm', 3.194),
(b'u', 2.364),
(b'd', 2.296),
(b'c', 2.163),
(b'b', 1.739),
(b'f', 1.625),
(b'6', 0.666),
(b'j', 0.610),
(b'y', 0.554),
(b'x', 0.487),
(b'w', 0.477),
(b'k', 0.476),
(b'v', 0.473),
(b'3', 0.336),
(b'1', 0.335),
(b'2', 0.326),
(b'4', 0.310),
(b'5', 0.305),
(b'9', 0.302),
(b'8', 0.300),
(b'7', 0.299),
(b'q', 0.298),
(b'0', 0.250),
(b'z', 0.223),
(b'-', 0.118),
(b'C', 0.095),
(b'T', 0.087),
(b'F', 0.085),
(b'B', 0.077),
(b'S', 0.076),
(b'P', 0.076),
(b'L', 0.059),
(b'A', 0.058),
(b'N', 0.051),
(b'D', 0.049),
(b'M', 0.046),
(b'E', 0.039),
(b'I', 0.035),
(b'R', 0.035),
(b'G', 0.028),
(b'U', 0.026),
(b'W', 0.025),
(b'O', 0.017),
(b'V', 0.015),
(b'H', 0.013),
(b'Q', 0.011),
(b'J', 0.007),
(b'K', 0.005),
(b'+', 0.004),
(b'X', 0.003),
(b'Y', 0.001),
)
for c, _ in probtable:
validchars.remove(c)
validchars = list(validchars)
def pickfrom(rng, table):
c = 0
r = rng.random() * sum(i[1] for i in table)
for i, p in table:
c += p
if c >= r:
return i
reservedcombos = casecombinations(winreserved)
# The first component of a name following a slash.
firsttable = (
(lambda rng: pickfrom(rng, probtable), 90),
(lambda rng: rng.choice(validchars), 5),
(lambda rng: rng.choice(reservedcombos), 5),
)
# Components of a name following the first.
resttable = firsttable[:-1]
# Special suffixes.
internalsuffixcombos = casecombinations(b'.hg .i .d'.split())
# The last component of a path, before a slash or at the end of a name.
lasttable = resttable + (
(lambda rng: b'', 95),
(lambda rng: rng.choice(internalsuffixcombos), 5),
)
def makepart(rng, k):
'''Construct a part of a pathname, without slashes.'''
p = pickfrom(rng, firsttable)(rng)
l = len(p)
ps = [p]
maxl = rng.randint(1, k)
while l < maxl:
p = pickfrom(rng, resttable)(rng)
l += len(p)
ps.append(p)
ps.append(pickfrom(rng, lasttable)(rng))
return b''.join(ps)
def makepath(rng, j, k):
'''Construct a complete pathname.'''
return (
b'data/'
+ b'/'.join(makepart(rng, k) for _ in range(j))
+ rng.choice([b'.d', b'.i'])
)
def genpath(rng, count):
'''Generate random pathnames with gradually increasing lengths.'''
mink, maxk = 1, 4096
def steps():
for i in range(count):
yield mink + int(round(math.sqrt((maxk - mink) * float(i) / count)))
for k in steps():
x = rng.randint(1, k)
y = rng.randint(1, k)
yield makepath(rng, x, y)
def runtests(rng, seed, count):
nerrs = 0
for p in genpath(rng, count):
h = store._pathencode(p) # uses C implementation, if available
r = store._hybridencode(p, True) # reference implementation in Python
if h != r:
if nerrs == 0:
print('seed:', hex(seed)[:-1], file=sys.stderr)
print("\np: '%s'" % p.encode("string_escape"), file=sys.stderr)
print("h: '%s'" % h.encode("string_escape"), file=sys.stderr)
print("r: '%s'" % r.encode("string_escape"), file=sys.stderr)
nerrs += 1
return nerrs
def main():
import getopt
# Empirically observed to take about a second to run
count = 100
seed = None
opts, args = getopt.getopt(
sys.argv[1:], 'c:s:', ['build', 'count=', 'seed=']
)
for o, a in opts:
if o in ('-c', '--count'):
count = int(a)
elif o in ('-s', '--seed'):
seed = int(a, base=0) # accepts base 10 or 16 strings
elif o == '--build':
buildprobtable(
sys.stdout,
'find .hg/store/data -type f && '
'cat .hg/store/fncache 2>/dev/null',
)
sys.exit(0)
if seed is None:
try:
seed = int(binascii.hexlify(os.urandom(16)), 16)
except AttributeError:
seed = int(time.time() * 1000)
rng = random.Random(seed)
if runtests(rng, seed, count):
sys.exit(1)
if __name__ == '__main__':
main()