Mercurial > hg
view mercurial/ancestor.py @ 26379:39d643252b9f
revlog: use existing file handle when reading during _addrevision
_addrevision() may need to read from revlogs as part of computing
deltas. Previously, we would flush existing file handles and open
a new, short-lived file handle to perform the reading.
If we have an existing file handle, it seems logical to reuse it
for reading instead of opening a new file handle. This patch
makes that the new behavior.
After this patch, revlog files are only reopened when adding
revisions if the revlog is switched from inline to non-inline.
On Linux when unbundling a bundle of the mozilla-central repo, this
patch has the following impact on system call counts:
Call Before After Delta
write 827,639 673,390 -154,249
open 700,103 684,089 -16,014
read 74,489 74,489 0
fstat 493,924 461,896 -32,028
close 249,131 233,117 -16,014
stat 242,001 242,001 0
lstat 18,676 18,676 0
lseek 20,268 20,268 0
ioctl 14,652 13,173 -1,479
TOTAL 3,180,758 2,930,679 -250,079
It's worth noting that many of the open() calls fail due to missing
files. That's why there are many more open() calls than close().
Despite the significant system call reduction, this change does not
seem to have a significant performance impact on Linux.
On Windows 10 (not a VM, on a SSD), this patch appears to reduce
unbundle time for mozilla-central from ~960s to ~920s. This isn't
as significant as I was hoping. But a decrease it is nonetheless.
Still, Windows unbundle performance is still >2x slower than Linux.
Despite the lack of significant gains, fewer system calls is fewer
system calls. If nothing else, this will narrow the focus of potential
areas to optimize in the future.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Sun, 27 Sep 2015 16:08:18 -0700 |
parents | 7ef98b38163f |
children | ead25aa27a43 |
line wrap: on
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# ancestor.py - generic DAG ancestor algorithm for mercurial # # Copyright 2006 Matt Mackall <mpm@selenic.com> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. from __future__ import absolute_import import collections import heapq from .node import nullrev def commonancestorsheads(pfunc, *nodes): """Returns a set with the heads of all common ancestors of all nodes, heads(::nodes[0] and ::nodes[1] and ...) . pfunc must return a list of parent vertices for a given vertex. """ if not isinstance(nodes, set): nodes = set(nodes) if nullrev in nodes: return set() if len(nodes) <= 1: return nodes allseen = (1 << len(nodes)) - 1 seen = [0] * (max(nodes) + 1) for i, n in enumerate(nodes): seen[n] = 1 << i poison = 1 << (i + 1) gca = set() interesting = len(nodes) nv = len(seen) - 1 while nv >= 0 and interesting: v = nv nv -= 1 if not seen[v]: continue sv = seen[v] if sv < poison: interesting -= 1 if sv == allseen: gca.add(v) sv |= poison if v in nodes: # history is linear return set([v]) if sv < poison: for p in pfunc(v): sp = seen[p] if p == nullrev: continue if sp == 0: seen[p] = sv interesting += 1 elif sp != sv: seen[p] |= sv else: for p in pfunc(v): if p == nullrev: continue sp = seen[p] if sp and sp < poison: interesting -= 1 seen[p] = sv return gca def ancestors(pfunc, *orignodes): """ Returns the common ancestors of a and b that are furthest from a root (as measured by longest path). pfunc must return a list of parent vertices for a given vertex. """ def deepest(nodes): interesting = {} count = max(nodes) + 1 depth = [0] * count seen = [0] * count mapping = [] for (i, n) in enumerate(sorted(nodes)): depth[n] = 1 b = 1 << i seen[n] = b interesting[b] = 1 mapping.append((b, n)) nv = count - 1 while nv >= 0 and len(interesting) > 1: v = nv nv -= 1 dv = depth[v] if dv == 0: continue sv = seen[v] for p in pfunc(v): if p == nullrev: continue dp = depth[p] nsp = sp = seen[p] if dp <= dv: depth[p] = dv + 1 if sp != sv: interesting[sv] += 1 nsp = seen[p] = sv if sp: interesting[sp] -= 1 if interesting[sp] == 0: del interesting[sp] elif dv == dp - 1: nsp = sp | sv if nsp == sp: continue seen[p] = nsp interesting.setdefault(nsp, 0) interesting[nsp] += 1 interesting[sp] -= 1 if interesting[sp] == 0: del interesting[sp] interesting[sv] -= 1 if interesting[sv] == 0: del interesting[sv] if len(interesting) != 1: return [] k = 0 for i in interesting: k |= i return set(n for (i, n) in mapping if k & i) gca = commonancestorsheads(pfunc, *orignodes) if len(gca) <= 1: return gca return deepest(gca) class incrementalmissingancestors(object): '''persistent state used to calculate missing ancestors incrementally Although similar in spirit to lazyancestors below, this is a separate class because trying to support contains and missingancestors operations with the same internal data structures adds needless complexity.''' def __init__(self, pfunc, bases): self.bases = set(bases) if not self.bases: self.bases.add(nullrev) self.pfunc = pfunc def hasbases(self): '''whether the common set has any non-trivial bases''' return self.bases and self.bases != set([nullrev]) def addbases(self, newbases): '''grow the ancestor set by adding new bases''' self.bases.update(newbases) def removeancestorsfrom(self, revs): '''remove all ancestors of bases from the set revs (in place)''' bases = self.bases pfunc = self.pfunc revs.difference_update(bases) # nullrev is always an ancestor revs.discard(nullrev) if not revs: return # anything in revs > start is definitely not an ancestor of bases # revs <= start needs to be investigated start = max(bases) keepcount = sum(1 for r in revs if r > start) if len(revs) == keepcount: # no revs to consider return for curr in xrange(start, min(revs) - 1, -1): if curr not in bases: continue revs.discard(curr) bases.update(pfunc(curr)) if len(revs) == keepcount: # no more potential revs to discard break def missingancestors(self, revs): '''return all the ancestors of revs that are not ancestors of self.bases This may include elements from revs. Equivalent to the revset (::revs - ::self.bases). Revs are returned in revision number order, which is a topological order.''' revsvisit = set(revs) basesvisit = self.bases pfunc = self.pfunc bothvisit = revsvisit.intersection(basesvisit) revsvisit.difference_update(bothvisit) if not revsvisit: return [] start = max(max(revsvisit), max(basesvisit)) # At this point, we hold the invariants that: # - revsvisit is the set of nodes we know are an ancestor of at least # one of the nodes in revs # - basesvisit is the same for bases # - bothvisit is the set of nodes we know are ancestors of at least one # of the nodes in revs and one of the nodes in bases. bothvisit and # revsvisit are mutually exclusive, but bothvisit is a subset of # basesvisit. # Now we walk down in reverse topo order, adding parents of nodes # already visited to the sets while maintaining the invariants. When a # node is found in both revsvisit and basesvisit, it is removed from # revsvisit and added to bothvisit. When revsvisit becomes empty, there # are no more ancestors of revs that aren't also ancestors of bases, so # exit. missing = [] for curr in xrange(start, nullrev, -1): if not revsvisit: break if curr in bothvisit: bothvisit.remove(curr) # curr's parents might have made it into revsvisit through # another path for p in pfunc(curr): revsvisit.discard(p) basesvisit.add(p) bothvisit.add(p) continue if curr in revsvisit: missing.append(curr) revsvisit.remove(curr) thisvisit = revsvisit othervisit = basesvisit elif curr in basesvisit: thisvisit = basesvisit othervisit = revsvisit else: # not an ancestor of revs or bases: ignore continue for p in pfunc(curr): if p == nullrev: pass elif p in othervisit or p in bothvisit: # p is implicitly in thisvisit. This means p is or should be # in bothvisit revsvisit.discard(p) basesvisit.add(p) bothvisit.add(p) else: # visit later thisvisit.add(p) missing.reverse() return missing class lazyancestors(object): def __init__(self, pfunc, revs, stoprev=0, inclusive=False): """Create a new object generating ancestors for the given revs. Does not generate revs lower than stoprev. This is computed lazily starting from revs. The object supports iteration and membership. cl should be a changelog and revs should be an iterable. inclusive is a boolean that indicates whether revs should be included. Revs lower than stoprev will not be generated. Result does not include the null revision.""" self._parentrevs = pfunc self._initrevs = revs self._stoprev = stoprev self._inclusive = inclusive # Initialize data structures for __contains__. # For __contains__, we use a heap rather than a deque because # (a) it minimizes the number of parentrevs calls made # (b) it makes the loop termination condition obvious # Python's heap is a min-heap. Multiply all values by -1 to convert it # into a max-heap. self._containsvisit = [-rev for rev in revs] heapq.heapify(self._containsvisit) if inclusive: self._containsseen = set(revs) else: self._containsseen = set() def __nonzero__(self): """False if the set is empty, True otherwise.""" try: iter(self).next() return True except StopIteration: return False def __iter__(self): """Generate the ancestors of _initrevs in reverse topological order. If inclusive is False, yield a sequence of revision numbers starting with the parents of each revision in revs, i.e., each revision is *not* considered an ancestor of itself. Results are in breadth-first order: parents of each rev in revs, then parents of those, etc. If inclusive is True, yield all the revs first (ignoring stoprev), then yield all the ancestors of revs as when inclusive is False. If an element in revs is an ancestor of a different rev it is not yielded again.""" seen = set() revs = self._initrevs if self._inclusive: for rev in revs: yield rev seen.update(revs) parentrevs = self._parentrevs stoprev = self._stoprev visit = collections.deque(revs) see = seen.add schedule = visit.append while visit: for parent in parentrevs(visit.popleft()): if parent >= stoprev and parent not in seen: schedule(parent) see(parent) yield parent def __contains__(self, target): """Test whether target is an ancestor of self._initrevs.""" # Trying to do both __iter__ and __contains__ using the same visit # heap and seen set is complex enough that it slows down both. Keep # them separate. seen = self._containsseen if target in seen: return True parentrevs = self._parentrevs visit = self._containsvisit stoprev = self._stoprev heappop = heapq.heappop heappush = heapq.heappush see = seen.add targetseen = False while visit and -visit[0] > target and not targetseen: for parent in parentrevs(-heappop(visit)): if parent < stoprev or parent in seen: continue # We need to make sure we push all parents into the heap so # that we leave it in a consistent state for future calls. heappush(visit, -parent) see(parent) if parent == target: targetseen = True return targetseen