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comparison mercurial/util.py @ 39569:cc23c09bc562

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util: optimize cost auditing on insert Calling popoldest() on insert with cost auditing enabled introduces significant overhead. The primary reason for this overhead is that popoldest() needs to walk the linked list to find the first non-empty node. When we call popoldest() within a loop, this can become quadratic. The performance impact is more pronounced on caches with large capacities. This commit effectively inlines the popoldest() call into _enforcecostlimit(). By doing so, we only do the backwards walk to find the first empty node once. However, we still may still perform this work on insert when the cache is near cost capacity. So this is only a partial performance win. $ hg perflrucachedict --size 4 --gets 1000000 --sets 1000000 --mixed 1000000 --costlimit 100 ! gets w/ cost limit ! wall 0.598737 comb 0.590000 user 0.590000 sys 0.000000 (best of 17) ! inserts w/ cost limit ! wall 1.694282 comb 1.700000 user 1.700000 sys 0.000000 (best of 6) ! wall 1.659181 comb 1.650000 user 1.650000 sys 0.000000 (best of 7) ! mixed w/ cost limit ! wall 1.157655 comb 1.150000 user 1.150000 sys 0.000000 (best of 9) ! wall 1.139955 comb 1.140000 user 1.140000 sys 0.000000 (best of 9) $ hg perflrucachedict --size 1000 --gets 1000000 --sets 1000000 --mixed 1000000 --costlimit 10000 ! gets w/ cost limit ! wall 0.598526 comb 0.600000 user 0.600000 sys 0.000000 (best of 17) ! wall 0.601993 comb 0.600000 user 0.600000 sys 0.000000 (best of 17) ! inserts w/ cost limit ! wall 37.838315 comb 37.840000 user 37.840000 sys 0.000000 (best of 3) ! wall 25.105273 comb 25.080000 user 25.080000 sys 0.000000 (best of 3) ! mixed w/ cost limit ! wall 18.060198 comb 18.060000 user 18.060000 sys 0.000000 (best of 3) ! wall 12.104470 comb 12.070000 user 12.070000 sys 0.000000 (best of 3) $ hg perflrucachedict --size 1000 --gets 1000000 --sets 1000000 --mixed 1000000 --costlimit 10000 --mixedgetfreq 90 ! gets w/ cost limit ! wall 0.600024 comb 0.600000 user 0.600000 sys 0.000000 (best of 17) ! wall 0.614439 comb 0.620000 user 0.620000 sys 0.000000 (best of 17) ! inserts w/ cost limit ! wall 37.154547 comb 37.120000 user 37.120000 sys 0.000000 (best of 3) ! wall 25.963028 comb 25.960000 user 25.960000 sys 0.000000 (best of 3) ! mixed w/ cost limit ! wall 4.381602 comb 4.380000 user 4.370000 sys 0.010000 (best of 3) ! wall 3.174256 comb 3.170000 user 3.170000 sys 0.000000 (best of 4) Differential Revision: https://phab.mercurial-scm.org/D4504
author Gregory Szorc <gregory.szorc@gmail.com>
date Thu, 06 Sep 2018 12:40:30 -0700
parents 842cd0bdda75
children f296c0b366c8
comparison
equal deleted inserted replaced
39568:842cd0bdda75 39569:cc23c09bc562
1462 1462
1463 def _enforcecostlimit(self): 1463 def _enforcecostlimit(self):
1464 # This should run after an insertion. It should only be called if total 1464 # This should run after an insertion. It should only be called if total
1465 # cost limits are being enforced. 1465 # cost limits are being enforced.
1466 # The most recently inserted node is never evicted. 1466 # The most recently inserted node is never evicted.
1467 if len(self) <= 1 or self.totalcost <= self.maxcost:
1468 return
1469
1470 # This is logically equivalent to calling popoldest() until we
1471 # free up enough cost. We don't do that since popoldest() needs
1472 # to walk the linked list and doing this in a loop would be
1473 # quadratic. So we find the first non-empty node and then
1474 # walk nodes until we free up enough capacity.
1475 n = self._head.prev
1476 while n.key is _notset:
1477 n = n.prev
1478
1467 while len(self) > 1 and self.totalcost > self.maxcost: 1479 while len(self) > 1 and self.totalcost > self.maxcost:
1468 self.popoldest() 1480 del self._cache[n.key]
1481 self.totalcost -= n.cost
1482 n.markempty()
1483 n = n.prev
1469 1484
1470 def lrucachefunc(func): 1485 def lrucachefunc(func):
1471 '''cache most recent results of function calls''' 1486 '''cache most recent results of function calls'''
1472 cache = {} 1487 cache = {}
1473 order = collections.deque() 1488 order = collections.deque()