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revlog: change generaldelta delta parent heuristic...
revlog: change generaldelta delta parent heuristic The old generaldelta heuristic was "if p1 (or p2) was closer than the last full text, use it, otherwise use prev". This was problematic when a repo contained multiple branches that were very different. If commits to branch A were pushed, and the last full text was branch B, it would generate a fulltext. Then if branch B was pushed, it would generate another fulltext. The problem is that the last fulltext (and delta'ing against `prev` in general) has no correlation with the contents of the incoming revision, and therefore will always have degenerate cases. According to the blame, that algorithm was chosen to minimize the chain length. Since there is already code that protects against that (the delta-vs-fulltext code), and since it has been improved since the original generaldelta algorithm went in (2011), I believe the chain length criteria will still be preserved. The new algorithm always diffs against p1 (or p2 if it's closer), unless the resulting delta will fail the delta-vs-fulltext check, in which case we delta against prev. Some before and after stats on manifest.d size. internal large repo old heuristic - 2.0 GB new heuristic - 1.2 GB mozilla-central old heuristic - 242 MB new heuristic - 261 MB The regression in mozilla central is due to the new heuristic choosing p2r as the delta when it's closer to the tip. Switching the algorithm to always prefer p1r brings the size back down (242 MB). This is result of the way in which mozilla does merges and pushes, and the result could easily swing the other direction in other repos (depending on if they merge X into Y or Y into X), but will never be as degenerate as before. I future patch will address the regression by introducing an optional, even more aggressive delta heuristic which will knock the mozilla manifest size down dramatically.

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revsetbenchmarks.py
319 lines | 9.7 KiB | text/x-python | PythonLexer
#!/usr/bin/env python
# Measure the performance of a list of revsets against multiple revisions
# defined by parameter. Checkout one by one and run perfrevset with every
# revset in the list to benchmark its performance.
#
# You should run this from the root of your mercurial repository.
#
# call with --help for details
import sys
import os
import re
import math
from subprocess import check_call, Popen, CalledProcessError, STDOUT, PIPE
# cannot use argparse, python 2.7 only
from optparse import OptionParser
DEFAULTVARIANTS = ['plain', 'min', 'max', 'first', 'last',
'reverse', 'reverse+first', 'reverse+last',
'sort', 'sort+first', 'sort+last']
def check_output(*args, **kwargs):
kwargs.setdefault('stderr', PIPE)
kwargs.setdefault('stdout', PIPE)
proc = Popen(*args, **kwargs)
output, error = proc.communicate()
if proc.returncode != 0:
raise CalledProcessError(proc.returncode, ' '.join(args[0]))
return output
def update(rev):
"""update the repo to a revision"""
try:
check_call(['hg', 'update', '--quiet', '--check', str(rev)])
check_output(['make', 'local'],
stderr=None) # suppress output except for error/warning
except CalledProcessError as exc:
print >> sys.stderr, 'update to revision %s failed, aborting' % rev
sys.exit(exc.returncode)
def hg(cmd, repo=None):
"""run a mercurial command
<cmd> is the list of command + argument,
<repo> is an optional repository path to run this command in."""
fullcmd = ['./hg']
if repo is not None:
fullcmd += ['-R', repo]
fullcmd += ['--config',
'extensions.perf=' + os.path.join(contribdir, 'perf.py')]
fullcmd += cmd
return check_output(fullcmd, stderr=STDOUT)
def perf(revset, target=None):
"""run benchmark for this very revset"""
try:
output = hg(['perfrevset', revset], repo=target)
return parseoutput(output)
except CalledProcessError as exc:
print >> sys.stderr, 'abort: cannot run revset benchmark: %s' % exc.cmd
if exc.output is None:
print >> sys.stderr, '(no ouput)'
else:
print >> sys.stderr, exc.output
return None
outputre = re.compile(r'! wall (\d+.\d+) comb (\d+.\d+) user (\d+.\d+) '
'sys (\d+.\d+) \(best of (\d+)\)')
def parseoutput(output):
"""parse a textual output into a dict
We cannot just use json because we want to compare with old
versions of Mercurial that may not support json output.
"""
match = outputre.search(output)
if not match:
print >> sys.stderr, 'abort: invalid output:'
print >> sys.stderr, output
sys.exit(1)
return {'comb': float(match.group(2)),
'count': int(match.group(5)),
'sys': float(match.group(3)),
'user': float(match.group(4)),
'wall': float(match.group(1)),
}
def printrevision(rev):
"""print data about a revision"""
sys.stdout.write("Revision ")
sys.stdout.flush()
check_call(['hg', 'log', '--rev', str(rev), '--template',
'{if(tags, " ({tags})")} '
'{rev}:{node|short}: {desc|firstline}\n'])
def idxwidth(nbidx):
"""return the max width of number used for index
This is similar to log10(nbidx), but we use custom code here
because we start with zero and we'd rather not deal with all the
extra rounding business that log10 would imply.
"""
nbidx -= 1 # starts at 0
idxwidth = 0
while nbidx:
idxwidth += 1
nbidx //= 10
if not idxwidth:
idxwidth = 1
return idxwidth
def getfactor(main, other, field, sensitivity=0.05):
"""return the relative factor between values for 'field' in main and other
Return None if the factor is insignicant (less than <sensitivity>
variation)."""
factor = 1
if main is not None:
factor = other[field] / main[field]
low, high = 1 - sensitivity, 1 + sensitivity
if (low < factor < high):
return None
return factor
def formatfactor(factor):
"""format a factor into a 4 char string
22%
156%
x2.4
x23
x789
x1e4
x5x7
"""
if factor is None:
return ' '
elif factor < 2:
return '%3i%%' % (factor * 100)
elif factor < 10:
return 'x%3.1f' % factor
elif factor < 1000:
return '%4s' % ('x%i' % factor)
else:
order = int(math.log(factor)) + 1
while 1 < math.log(factor):
factor //= 0
return 'x%ix%i' % (factor, order)
def formattiming(value):
"""format a value to strictly 8 char, dropping some precision if needed"""
if value < 10**7:
return ('%.6f' % value)[:8]
else:
# value is HUGE very unlikely to happen (4+ month run)
return '%i' % value
_marker = object()
def printresult(variants, idx, data, maxidx, verbose=False, reference=_marker):
"""print a line of result to stdout"""
mask = '%%0%ii) %%s' % idxwidth(maxidx)
out = []
for var in variants:
if data[var] is None:
out.append('error ')
out.append(' ' * 4)
continue
out.append(formattiming(data[var]['wall']))
if reference is not _marker:
factor = None
if reference is not None:
factor = getfactor(reference[var], data[var], 'wall')
out.append(formatfactor(factor))
if verbose:
out.append(formattiming(data[var]['comb']))
out.append(formattiming(data[var]['user']))
out.append(formattiming(data[var]['sys']))
out.append('%6d' % data[var]['count'])
print mask % (idx, ' '.join(out))
def printheader(variants, maxidx, verbose=False, relative=False):
header = [' ' * (idxwidth(maxidx) + 1)]
for var in variants:
if not var:
var = 'iter'
if 8 < len(var):
var = var[:3] + '..' + var[-3:]
header.append('%-8s' % var)
if relative:
header.append(' ')
if verbose:
header.append('%-8s' % 'comb')
header.append('%-8s' % 'user')
header.append('%-8s' % 'sys')
header.append('%6s' % 'count')
print ' '.join(header)
def getrevs(spec):
"""get the list of rev matched by a revset"""
try:
out = check_output(['hg', 'log', '--template={rev}\n', '--rev', spec])
except CalledProcessError as exc:
print >> sys.stderr, "abort, can't get revision from %s" % spec
sys.exit(exc.returncode)
return [r for r in out.split() if r]
def applyvariants(revset, variant):
if variant == 'plain':
return revset
for var in variant.split('+'):
revset = '%s(%s)' % (var, revset)
return revset
helptext="""This script will run multiple variants of provided revsets using
different revisions in your mercurial repository. After the benchmark are run
summary output is provided. Use itto demonstrate speed improvements or pin
point regressions. Revsets to run are specified in a file (or from stdin), one
revsets per line. Line starting with '#' will be ignored, allowing insertion of
comments."""
parser = OptionParser(usage="usage: %prog [options] <revs>",
description=helptext)
parser.add_option("-f", "--file",
help="read revset from FILE (stdin if omitted)",
metavar="FILE")
parser.add_option("-R", "--repo",
help="run benchmark on REPO", metavar="REPO")
parser.add_option("-v", "--verbose",
action='store_true',
help="display all timing data (not just best total time)")
parser.add_option("", "--variants",
default=','.join(DEFAULTVARIANTS),
help="comma separated list of variant to test "
"(eg: plain,min,sorted) (plain = no modification)")
(options, args) = parser.parse_args()
if not args:
parser.print_help()
sys.exit(255)
# the directory where both this script and the perf.py extension live.
contribdir = os.path.dirname(__file__)
revsetsfile = sys.stdin
if options.file:
revsetsfile = open(options.file)
revsets = [l.strip() for l in revsetsfile if not l.startswith('#')]
revsets = [l for l in revsets if l]
print "Revsets to benchmark"
print "----------------------------"
for idx, rset in enumerate(revsets):
print "%i) %s" % (idx, rset)
print "----------------------------"
print
revs = []
for a in args:
revs.extend(getrevs(a))
variants = options.variants.split(',')
results = []
for r in revs:
print "----------------------------"
printrevision(r)
print "----------------------------"
update(r)
res = []
results.append(res)
printheader(variants, len(revsets), verbose=options.verbose)
for idx, rset in enumerate(revsets):
varres = {}
for var in variants:
varrset = applyvariants(rset, var)
data = perf(varrset, target=options.repo)
varres[var] = data
res.append(varres)
printresult(variants, idx, varres, len(revsets),
verbose=options.verbose)
sys.stdout.flush()
print "----------------------------"
print """
Result by revset
================
"""
print 'Revision:'
for idx, rev in enumerate(revs):
sys.stdout.write('%i) ' % idx)
sys.stdout.flush()
printrevision(rev)
print
print
for ridx, rset in enumerate(revsets):
print "revset #%i: %s" % (ridx, rset)
printheader(variants, len(results), verbose=options.verbose, relative=True)
ref = None
for idx, data in enumerate(results):
printresult(variants, idx, data[ridx], len(results),
verbose=options.verbose, reference=ref)
ref = data[ridx]
print