perf: add threading capability to perfbdiff
Since we are releasing the GIL during diffing, it is interesting to see how a
thread pool would perform on diffing. We add a new `--threads` argument to
commands. Synchronizing the thread pool is a bit complex because we want to be
able to reuse it from one run to another.
On my computer (i7 with 4 cores + hyperthreading), I get the following data for
about 12000 revisions:
threads wall comb wall gain comb overhead
none 31.596715 31.59 0.00% 0.00%
1 31.621228 31.62 -0.08% 0.09%
2 16.406202 32.8 48.08% 3.83%
3 11.598334 34.76 63.29% 10.03%
4 9.205421 36.77 70.87% 16.40%
5 8.517604 42.51 73.04% 34.57%
6 7.94645 47.58 74.85% 50.62%
7 7.434972 51.92 76.47% 64.36%
8 7.070638 55.34 77.62% 75.18%
Compared to the feature disabled (threads=0), the overhead is negligible with
the threading code (threads=1), and the gain is already 48% with two threads.
from __future__ import absolute_import, print_function
from mercurial import (
util,
)
def printifpresent(d, xs, name='d'):
for x in xs:
present = x in d
print("'%s' in %s: %s" % (x, name, present))
if present:
print("%s['%s']: %s" % (name, x, d[x]))
def test_lrucachedict():
d = util.lrucachedict(4)
d['a'] = 'va'
d['b'] = 'vb'
d['c'] = 'vc'
d['d'] = 'vd'
# all of these should be present
printifpresent(d, ['a', 'b', 'c', 'd'])
# 'a' should be dropped because it was least recently used
d['e'] = 've'
printifpresent(d, ['a', 'b', 'c', 'd', 'e'])
assert d.get('a') is None
assert d.get('e') == 've'
# touch entries in some order (get or set).
d['e']
d['c'] = 'vc2'
d['d']
d['b'] = 'vb2'
# 'e' should be dropped now
d['f'] = 'vf'
printifpresent(d, ['b', 'c', 'd', 'e', 'f'])
d.clear()
printifpresent(d, ['b', 'c', 'd', 'e', 'f'])
# Now test dicts that aren't full.
d = util.lrucachedict(4)
d['a'] = 1
d['b'] = 2
d['a']
d['b']
printifpresent(d, ['a', 'b'])
# test copy method
d = util.lrucachedict(4)
d['a'] = 'va3'
d['b'] = 'vb3'
d['c'] = 'vc3'
d['d'] = 'vd3'
dc = d.copy()
# all of these should be present
print("\nAll of these should be present:")
printifpresent(dc, ['a', 'b', 'c', 'd'], 'dc')
# 'a' should be dropped because it was least recently used
print("\nAll of these except 'a' should be present:")
dc['e'] = 've3'
printifpresent(dc, ['a', 'b', 'c', 'd', 'e'], 'dc')
# contents and order of original dict should remain unchanged
print("\nThese should be in reverse alphabetical order and read 'v?3':")
dc['b'] = 'vb3_new'
for k in list(iter(d)):
print("d['%s']: %s" % (k, d[k]))
if __name__ == '__main__':
test_lrucachedict()