Mercurial > hg
view mercurial/error.py @ 29830:92ac2baaea86
revlog: use an LRU cache for delta chain bases
Profiling using statprof revealed a hotspot during changegroup
application calculating delta chain bases on generaldelta repos.
Essentially, revlog._addrevision() was performing a lot of redundant
work tracing the delta chain as part of determining when the chain
distance was acceptable. This was most pronounced when adding
revisions to manifests, which can have delta chains thousands of
revisions long.
There was a delta chain base cache on revlogs before, but it only
captured a single revision. This was acceptable before generaldelta,
when _addrevision would build deltas from the previous revision and
thus we'd pretty much guarantee a cache hit when resolving the delta
chain base on a subsequent _addrevision call. However, it isn't
suitable for generaldelta because parent revisions aren't necessarily
the last processed revision.
This patch converts the delta chain base cache to an LRU dict cache.
The cache can hold multiple entries, so generaldelta repos have a
higher chance of getting a cache hit.
The impact of this change when processing changegroup additions is
significant. On a generaldelta conversion of the "mozilla-unified"
repo (which contains heads of the main Firefox repositories in
chronological order - this means there are lots of transitions between
heads in revlog order), this change has the following impact when
performing an `hg unbundle` of an uncompressed bundle of the repo:
before: 5:42 CPU time
after: 4:34 CPU time
Most of this time is saved when applying the changelog and manifest
revlogs:
before: 2:30 CPU time
after: 1:17 CPU time
That nearly a 50% reduction in CPU time applying changesets and
manifests!
Applying a gzipped bundle of the same repo (effectively simulating a
`hg clone` over HTTP) showed a similar speedup:
before: 5:53 CPU time
after: 4:46 CPU time
Wall time improvements were basically the same as CPU time.
I didn't measure explicitly, but it feels like most of the time
is saved when processing manifests. This makes sense, as large
manifests tend to have very long delta chains and thus benefit the
most from this cache.
So, this change effectively makes changegroup application (which is
used by `hg unbundle`, `hg clone`, `hg pull`, `hg unshelve`, and
various other commands) significantly faster when delta chains are
long (which can happen on repos with large numbers of files and thus
large manifests).
In theory, this change can result in more memory utilization. However,
we're caching a dict of ints. At most we have 200 ints + Python object
overhead per revlog. And, the cache is really only populated when
performing read-heavy operations, such as adding changegroups or
scanning an individual revlog. For memory bloat to be an issue, we'd
need to scan/read several revisions from several revlogs all while
having active references to several revlogs. I don't think there are
many operations that do this, so I don't think memory bloat from the
cache will be an issue.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Mon, 22 Aug 2016 21:48:50 -0700 |
parents | b17a6e3cd2ac |
children | 318a24b52eeb |
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# error.py - Mercurial exceptions # # Copyright 2005-2008 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. """Mercurial exceptions. This allows us to catch exceptions at higher levels without forcing imports. """ from __future__ import absolute_import # Do not import anything here, please class Hint(object): """Mix-in to provide a hint of an error This should come first in the inheritance list to consume a hint and pass remaining arguments to the exception class. """ def __init__(self, *args, **kw): self.hint = kw.pop('hint', None) super(Hint, self).__init__(*args, **kw) class RevlogError(Hint, Exception): pass class FilteredIndexError(IndexError): pass class LookupError(RevlogError, KeyError): def __init__(self, name, index, message): self.name = name self.index = index # this can't be called 'message' because at least some installs of # Python 2.6+ complain about the 'message' property being deprecated self.lookupmessage = message if isinstance(name, str) and len(name) == 20: from .node import short name = short(name) RevlogError.__init__(self, '%s@%s: %s' % (index, name, message)) def __str__(self): return RevlogError.__str__(self) class FilteredLookupError(LookupError): pass class ManifestLookupError(LookupError): pass class CommandError(Exception): """Exception raised on errors in parsing the command line.""" class InterventionRequired(Hint, Exception): """Exception raised when a command requires human intervention.""" class Abort(Hint, Exception): """Raised if a command needs to print an error and exit.""" class HookLoadError(Abort): """raised when loading a hook fails, aborting an operation Exists to allow more specialized catching.""" class HookAbort(Abort): """raised when a validation hook fails, aborting an operation Exists to allow more specialized catching.""" class ConfigError(Abort): """Exception raised when parsing config files""" class UpdateAbort(Abort): """Raised when an update is aborted for destination issue""" class MergeDestAbort(Abort): """Raised when an update is aborted for destination issues""" class NoMergeDestAbort(MergeDestAbort): """Raised when an update is aborted because there is nothing to merge""" class ManyMergeDestAbort(MergeDestAbort): """Raised when an update is aborted because destination is ambigious""" class ResponseExpected(Abort): """Raised when an EOF is received for a prompt""" def __init__(self): from .i18n import _ Abort.__init__(self, _('response expected')) class OutOfBandError(Hint, Exception): """Exception raised when a remote repo reports failure""" class ParseError(Hint, Exception): """Raised when parsing config files and {rev,file}sets (msg[, pos])""" class UnknownIdentifier(ParseError): """Exception raised when a {rev,file}set references an unknown identifier""" def __init__(self, function, symbols): from .i18n import _ ParseError.__init__(self, _("unknown identifier: %s") % function) self.function = function self.symbols = symbols class RepoError(Hint, Exception): pass class RepoLookupError(RepoError): pass class FilteredRepoLookupError(RepoLookupError): pass class CapabilityError(RepoError): pass class RequirementError(RepoError): """Exception raised if .hg/requires has an unknown entry.""" class UnsupportedMergeRecords(Abort): def __init__(self, recordtypes): from .i18n import _ self.recordtypes = sorted(recordtypes) s = ' '.join(self.recordtypes) Abort.__init__( self, _('unsupported merge state records: %s') % s, hint=_('see https://mercurial-scm.org/wiki/MergeStateRecords for ' 'more information')) class LockError(IOError): def __init__(self, errno, strerror, filename, desc): IOError.__init__(self, errno, strerror, filename) self.desc = desc class LockHeld(LockError): def __init__(self, errno, filename, desc, locker): LockError.__init__(self, errno, 'Lock held', filename, desc) self.locker = locker class LockUnavailable(LockError): pass # LockError is for errors while acquiring the lock -- this is unrelated class LockInheritanceContractViolation(RuntimeError): pass class ResponseError(Exception): """Raised to print an error with part of output and exit.""" class UnknownCommand(Exception): """Exception raised if command is not in the command table.""" class AmbiguousCommand(Exception): """Exception raised if command shortcut matches more than one command.""" # derived from KeyboardInterrupt to simplify some breakout code class SignalInterrupt(KeyboardInterrupt): """Exception raised on SIGTERM and SIGHUP.""" class SignatureError(Exception): pass class PushRaced(RuntimeError): """An exception raised during unbundling that indicate a push race""" # bundle2 related errors class BundleValueError(ValueError): """error raised when bundle2 cannot be processed""" class BundleUnknownFeatureError(BundleValueError): def __init__(self, parttype=None, params=(), values=()): self.parttype = parttype self.params = params self.values = values if self.parttype is None: msg = 'Stream Parameter' else: msg = parttype entries = self.params if self.params and self.values: assert len(self.params) == len(self.values) entries = [] for idx, par in enumerate(self.params): val = self.values[idx] if val is None: entries.append(val) else: entries.append("%s=%r" % (par, val)) if entries: msg = '%s - %s' % (msg, ', '.join(entries)) ValueError.__init__(self, msg) class ReadOnlyPartError(RuntimeError): """error raised when code tries to alter a part being generated""" class PushkeyFailed(Abort): """error raised when a pushkey part failed to update a value""" def __init__(self, partid, namespace=None, key=None, new=None, old=None, ret=None): self.partid = partid self.namespace = namespace self.key = key self.new = new self.old = old self.ret = ret # no i18n expected to be processed into a better message Abort.__init__(self, 'failed to update value for "%s/%s"' % (namespace, key)) class CensoredNodeError(RevlogError): """error raised when content verification fails on a censored node Also contains the tombstone data substituted for the uncensored data. """ def __init__(self, filename, node, tombstone): from .node import short RevlogError.__init__(self, '%s:%s' % (filename, short(node))) self.tombstone = tombstone class CensoredBaseError(RevlogError): """error raised when a delta is rejected because its base is censored A delta based on a censored revision must be formed as single patch operation which replaces the entire base with new content. This ensures the delta may be applied by clones which have not censored the base. """ class InvalidBundleSpecification(Exception): """error raised when a bundle specification is invalid. This is used for syntax errors as opposed to support errors. """ class UnsupportedBundleSpecification(Exception): """error raised when a bundle specification is not supported.""" class CorruptedState(Exception): """error raised when a command is not able to read its state from file"""