Mercurial > hg
view mercurial/repocache.py @ 42743:8c9a6adec67a
rust-discovery: using the children cache in add_missing
The DAG range computation often needs to get back to very old
revisions, and turns out to be disproportionately long, given
that the end goal is to remove the descendents of the given
missing revisons from the undecided set.
The fast iteration capabilities available in the Rust case make
it possible to avoid the DAG range entirely, at the cost of
precomputing the children cache, and to simply iterate on
children of the given missing revisions.
This is a case where staying on the same side of the interface
between the two languages has clear benefits.
On discoveries with initial undecided sets
small enough to bypass sampling entirely, the total cost of
computing the children cache and the subsequent iteration
becomes better than the Python + C counterpart, which relies on
reachableroots2.
For example, on a repo with more than one million revisions with
an initial undecided set of 11 elements, we get these figures:
Rust version with simple iteration
addcommons: 57.287us
first undecided computation: 184.278334ms
first children cache computation: 131.056us
addmissings iteration: 42.766us
first addinfo total: 185.24 ms
Python + C version
first addcommons: 0.29 ms
addcommons 0.21 ms
first undecided computation 191.35 ms
addmissings 45.75 ms
first addinfo total: 237.77 ms
On discoveries with large undecided sets, the initial price paid
makes the first addinfo slower than the Python + C version,
but that's more than compensated by the gain in sampling and
subsequent iterations.
Here's an extreme example with an undecided set of a million revisions:
Rust version:
first undecided computation: 293.842629ms
first children cache computation: 407.911297ms
addmissings iteration: 34.312869ms
first addinfo total: 776.02 ms
taking initial sample
query 2: sampling time: 1318.38 ms
query 2; still undecided: 1005013, sample size is: 200
addmissings: 143.062us
Python + C version:
first undecided computation 298.13 ms
addmissings 80.13 ms
first addinfo total: 399.62 ms
taking initial sample
query 2: sampling time: 3957.23 ms
query 2; still undecided: 1005013, sample size is: 200
addmissings 52.88 ms
Differential Revision: https://phab.mercurial-scm.org/D6428
author | Georges Racinet <georges.racinet@octobus.net> |
---|---|
date | Tue, 16 Apr 2019 01:16:39 +0200 |
parents | dcac24ec935b |
children | 2372284d9457 |
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# repocache.py - in-memory repository cache for long-running services # # Copyright 2018 Yuya Nishihara <yuya@tcha.org> # # 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 gc import threading from . import ( error, hg, obsolete, scmutil, util, ) class repoloader(object): """Load repositories in background thread This is designed for a forking server. A cached repo cannot be obtained until the server fork()s a worker and the loader thread stops. """ def __init__(self, ui, maxlen): self._ui = ui.copy() self._cache = util.lrucachedict(max=maxlen) # use deque and Event instead of Queue since deque can discard # old items to keep at most maxlen items. self._inqueue = collections.deque(maxlen=maxlen) self._accepting = False self._newentry = threading.Event() self._thread = None def start(self): assert not self._thread if self._inqueue.maxlen == 0: # no need to spawn loader thread as the cache is disabled return self._accepting = True self._thread = threading.Thread(target=self._mainloop) self._thread.start() def stop(self): if not self._thread: return self._accepting = False self._newentry.set() self._thread.join() self._thread = None self._cache.clear() self._inqueue.clear() def load(self, path): """Request to load the specified repository in background""" self._inqueue.append(path) self._newentry.set() def get(self, path): """Return a cached repo if available This function must be called after fork(), where the loader thread is stopped. Otherwise, the returned repo might be updated by the loader thread. """ if self._thread and self._thread.is_alive(): raise error.ProgrammingError(b'cannot obtain cached repo while ' b'loader is active') return self._cache.peek(path, None) def _mainloop(self): while self._accepting: # Avoid heavy GC after fork(), which would cancel the benefit of # COW. We assume that GIL is acquired while GC is underway in the # loader thread. If that isn't true, we might have to move # gc.collect() to the main thread so that fork() would never stop # the thread where GC is in progress. gc.collect() self._newentry.wait() while self._accepting: self._newentry.clear() try: path = self._inqueue.popleft() except IndexError: break scmutil.callcatch(self._ui, lambda: self._load(path)) def _load(self, path): start = util.timer() # TODO: repo should be recreated if storage configuration changed try: # pop before loading so inconsistent state wouldn't be exposed repo = self._cache.pop(path) except KeyError: repo = hg.repository(self._ui, path).unfiltered() _warmupcache(repo) repo.ui.log(b'repocache', b'loaded repo into cache: %s (in %.3fs)\n', path, util.timer() - start) self._cache.insert(path, repo) # TODO: think about proper API of preloading cache def _warmupcache(repo): repo.invalidateall() repo.changelog repo.obsstore._all repo.obsstore.successors repo.obsstore.predecessors repo.obsstore.children for name in obsolete.cachefuncs: obsolete.getrevs(repo, name) repo._phasecache.loadphaserevs(repo) # TODO: think about proper API of attaching preloaded attributes def copycache(srcrepo, destrepo): """Copy cached attributes from srcrepo to destrepo""" destfilecache = destrepo._filecache srcfilecache = srcrepo._filecache if 'changelog' in srcfilecache: destfilecache['changelog'] = ce = srcfilecache['changelog'] ce.obj.opener = ce.obj._realopener = destrepo.svfs if 'obsstore' in srcfilecache: destfilecache['obsstore'] = ce = srcfilecache['obsstore'] ce.obj.svfs = destrepo.svfs if '_phasecache' in srcfilecache: destfilecache['_phasecache'] = ce = srcfilecache['_phasecache'] ce.obj.opener = destrepo.svfs