Mercurial > hg
view tests/f @ 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 | 318534bb5dfd |
children | c425b678df7c |
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#!/usr/bin/env python """ Utility for inspecting files in various ways. This tool is like the collection of tools found in a unix environment but are cross platform and stable and suitable for our needs in the test suite. This can be used instead of tools like: [ dd find head hexdump ls md5sum readlink sha1sum stat tail test readlink.py md5sum.py """ from __future__ import absolute_import import glob import hashlib import optparse import os import re import sys def visit(opts, filenames, outfile): """Process filenames in the way specified in opts, writing output to outfile.""" for f in sorted(filenames): isstdin = f == '-' if not isstdin and not os.path.lexists(f): outfile.write('%s: file not found\n' % f) continue quiet = opts.quiet and not opts.recurse or isstdin isdir = os.path.isdir(f) islink = os.path.islink(f) isfile = os.path.isfile(f) and not islink dirfiles = None content = None facts = [] if isfile: if opts.type: facts.append('file') if opts.hexdump or opts.dump or opts.md5: content = file(f, 'rb').read() elif islink: if opts.type: facts.append('link') content = os.readlink(f) elif isstdin: content = sys.stdin.read() if opts.size: facts.append('size=%s' % len(content)) elif isdir: if opts.recurse or opts.type: dirfiles = glob.glob(f + '/*') facts.append('directory with %s files' % len(dirfiles)) elif opts.type: facts.append('type unknown') if not isstdin: stat = os.lstat(f) if opts.size and not isdir: facts.append('size=%s' % stat.st_size) if opts.mode and not islink: facts.append('mode=%o' % (stat.st_mode & 0o777)) if opts.links: facts.append('links=%s' % stat.st_nlink) if opts.newer: # mtime might be in whole seconds so newer file might be same if stat.st_mtime >= os.stat(opts.newer).st_mtime: facts.append('newer than %s' % opts.newer) else: facts.append('older than %s' % opts.newer) if opts.md5 and content is not None: h = hashlib.md5(content) facts.append('md5=%s' % h.hexdigest()[:opts.bytes]) if opts.sha1 and content is not None: h = hashlib.sha1(content) facts.append('sha1=%s' % h.hexdigest()[:opts.bytes]) if isstdin: outfile.write(', '.join(facts) + '\n') elif facts: outfile.write('%s: %s\n' % (f, ', '.join(facts))) elif not quiet: outfile.write('%s:\n' % f) if content is not None: chunk = content if not islink: if opts.lines: if opts.lines >= 0: chunk = ''.join(chunk.splitlines(True)[:opts.lines]) else: chunk = ''.join(chunk.splitlines(True)[opts.lines:]) if opts.bytes: if opts.bytes >= 0: chunk = chunk[:opts.bytes] else: chunk = chunk[opts.bytes:] if opts.hexdump: for i in range(0, len(chunk), 16): s = chunk[i:i + 16] outfile.write('%04x: %-47s |%s|\n' % (i, ' '.join('%02x' % ord(c) for c in s), re.sub('[^ -~]', '.', s))) if opts.dump: if not quiet: outfile.write('>>>\n') outfile.write(chunk) if not quiet: if chunk.endswith('\n'): outfile.write('<<<\n') else: outfile.write('\n<<< no trailing newline\n') if opts.recurse and dirfiles: assert not isstdin visit(opts, dirfiles, outfile) if __name__ == "__main__": parser = optparse.OptionParser("%prog [options] [filenames]") parser.add_option("-t", "--type", action="store_true", help="show file type (file or directory)") parser.add_option("-m", "--mode", action="store_true", help="show file mode") parser.add_option("-l", "--links", action="store_true", help="show number of links") parser.add_option("-s", "--size", action="store_true", help="show size of file") parser.add_option("-n", "--newer", action="store", help="check if file is newer (or same)") parser.add_option("-r", "--recurse", action="store_true", help="recurse into directories") parser.add_option("-S", "--sha1", action="store_true", help="show sha1 hash of the content") parser.add_option("-M", "--md5", action="store_true", help="show md5 hash of the content") parser.add_option("-D", "--dump", action="store_true", help="dump file content") parser.add_option("-H", "--hexdump", action="store_true", help="hexdump file content") parser.add_option("-B", "--bytes", type="int", help="number of characters to dump") parser.add_option("-L", "--lines", type="int", help="number of lines to dump") parser.add_option("-q", "--quiet", action="store_true", help="no default output") (opts, filenames) = parser.parse_args(sys.argv[1:]) if not filenames: filenames = ['-'] visit(opts, filenames, sys.stdout)