Mercurial > hg
view mercurial/commandserver.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 | 591c3badff2e |
children | 7f2313450e86 |
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# commandserver.py - communicate with Mercurial's API over a pipe # # Copyright 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 errno import gc import os import random import select import signal import socket import struct import sys import traceback from .i18n import _ from . import ( encoding, error, util, ) logfile = None def log(*args): if not logfile: return for a in args: logfile.write(str(a)) logfile.flush() class channeledoutput(object): """ Write data to out in the following format: data length (unsigned int), data """ def __init__(self, out, channel): self.out = out self.channel = channel @property def name(self): return '<%c-channel>' % self.channel def write(self, data): if not data: return self.out.write(struct.pack('>cI', self.channel, len(data))) self.out.write(data) self.out.flush() def __getattr__(self, attr): if attr in ('isatty', 'fileno', 'tell', 'seek'): raise AttributeError(attr) return getattr(self.out, attr) class channeledinput(object): """ Read data from in_. Requests for input are written to out in the following format: channel identifier - 'I' for plain input, 'L' line based (1 byte) how many bytes to send at most (unsigned int), The client replies with: data length (unsigned int), 0 meaning EOF data """ maxchunksize = 4 * 1024 def __init__(self, in_, out, channel): self.in_ = in_ self.out = out self.channel = channel @property def name(self): return '<%c-channel>' % self.channel def read(self, size=-1): if size < 0: # if we need to consume all the clients input, ask for 4k chunks # so the pipe doesn't fill up risking a deadlock size = self.maxchunksize s = self._read(size, self.channel) buf = s while s: s = self._read(size, self.channel) buf += s return buf else: return self._read(size, self.channel) def _read(self, size, channel): if not size: return '' assert size > 0 # tell the client we need at most size bytes self.out.write(struct.pack('>cI', channel, size)) self.out.flush() length = self.in_.read(4) length = struct.unpack('>I', length)[0] if not length: return '' else: return self.in_.read(length) def readline(self, size=-1): if size < 0: size = self.maxchunksize s = self._read(size, 'L') buf = s # keep asking for more until there's either no more or # we got a full line while s and s[-1] != '\n': s = self._read(size, 'L') buf += s return buf else: return self._read(size, 'L') def __iter__(self): return self def next(self): l = self.readline() if not l: raise StopIteration return l def __getattr__(self, attr): if attr in ('isatty', 'fileno', 'tell', 'seek'): raise AttributeError(attr) return getattr(self.in_, attr) class server(object): """ Listens for commands on fin, runs them and writes the output on a channel based stream to fout. """ def __init__(self, ui, repo, fin, fout): self.cwd = os.getcwd() # developer config: cmdserver.log logpath = ui.config("cmdserver", "log", None) if logpath: global logfile if logpath == '-': # write log on a special 'd' (debug) channel logfile = channeledoutput(fout, 'd') else: logfile = open(logpath, 'a') if repo: # the ui here is really the repo ui so take its baseui so we don't # end up with its local configuration self.ui = repo.baseui self.repo = repo self.repoui = repo.ui else: self.ui = ui self.repo = self.repoui = None self.cerr = channeledoutput(fout, 'e') self.cout = channeledoutput(fout, 'o') self.cin = channeledinput(fin, fout, 'I') self.cresult = channeledoutput(fout, 'r') self.client = fin def cleanup(self): """release and restore resources taken during server session""" pass def _read(self, size): if not size: return '' data = self.client.read(size) # is the other end closed? if not data: raise EOFError return data def _readstr(self): """read a string from the channel format: data length (uint32), data """ length = struct.unpack('>I', self._read(4))[0] if not length: return '' return self._read(length) def _readlist(self): """read a list of NULL separated strings from the channel""" s = self._readstr() if s: return s.split('\0') else: return [] def runcommand(self): """ reads a list of \0 terminated arguments, executes and writes the return code to the result channel """ from . import dispatch # avoid cycle args = self._readlist() # copy the uis so changes (e.g. --config or --verbose) don't # persist between requests copiedui = self.ui.copy() uis = [copiedui] if self.repo: self.repo.baseui = copiedui # clone ui without using ui.copy because this is protected repoui = self.repoui.__class__(self.repoui) repoui.copy = copiedui.copy # redo copy protection uis.append(repoui) self.repo.ui = self.repo.dirstate._ui = repoui self.repo.invalidateall() for ui in uis: ui.resetstate() # any kind of interaction must use server channels, but chg may # replace channels by fully functional tty files. so nontty is # enforced only if cin is a channel. if not util.safehasattr(self.cin, 'fileno'): ui.setconfig('ui', 'nontty', 'true', 'commandserver') req = dispatch.request(args[:], copiedui, self.repo, self.cin, self.cout, self.cerr) ret = (dispatch.dispatch(req) or 0) & 255 # might return None # restore old cwd if '--cwd' in args: os.chdir(self.cwd) self.cresult.write(struct.pack('>i', int(ret))) def getencoding(self): """ writes the current encoding to the result channel """ self.cresult.write(encoding.encoding) def serveone(self): cmd = self.client.readline()[:-1] if cmd: handler = self.capabilities.get(cmd) if handler: handler(self) else: # clients are expected to check what commands are supported by # looking at the servers capabilities raise error.Abort(_('unknown command %s') % cmd) return cmd != '' capabilities = {'runcommand' : runcommand, 'getencoding' : getencoding} def serve(self): hellomsg = 'capabilities: ' + ' '.join(sorted(self.capabilities)) hellomsg += '\n' hellomsg += 'encoding: ' + encoding.encoding hellomsg += '\n' hellomsg += 'pid: %d' % util.getpid() if util.safehasattr(os, 'getpgid'): hellomsg += '\n' hellomsg += 'pgid: %d' % os.getpgid(0) # write the hello msg in -one- chunk self.cout.write(hellomsg) try: while self.serveone(): pass except EOFError: # we'll get here if the client disconnected while we were reading # its request return 1 return 0 def _protectio(ui): """ duplicates streams and redirect original to null if ui uses stdio """ ui.flush() newfiles = [] nullfd = os.open(os.devnull, os.O_RDWR) for f, sysf, mode in [(ui.fin, sys.stdin, 'rb'), (ui.fout, sys.stdout, 'wb')]: if f is sysf: newfd = os.dup(f.fileno()) os.dup2(nullfd, f.fileno()) f = os.fdopen(newfd, mode) newfiles.append(f) os.close(nullfd) return tuple(newfiles) def _restoreio(ui, fin, fout): """ restores streams from duplicated ones """ ui.flush() for f, uif in [(fin, ui.fin), (fout, ui.fout)]: if f is not uif: os.dup2(f.fileno(), uif.fileno()) f.close() class pipeservice(object): def __init__(self, ui, repo, opts): self.ui = ui self.repo = repo def init(self): pass def run(self): ui = self.ui # redirect stdio to null device so that broken extensions or in-process # hooks will never cause corruption of channel protocol. fin, fout = _protectio(ui) try: sv = server(ui, self.repo, fin, fout) return sv.serve() finally: sv.cleanup() _restoreio(ui, fin, fout) def _initworkerprocess(): # use a different process group from the master process, in order to: # 1. make the current process group no longer "orphaned" (because the # parent of this process is in a different process group while # remains in a same session) # according to POSIX 2.2.2.52, orphaned process group will ignore # terminal-generated stop signals like SIGTSTP (Ctrl+Z), which will # cause trouble for things like ncurses. # 2. the client can use kill(-pgid, sig) to simulate terminal-generated # SIGINT (Ctrl+C) and process-exit-generated SIGHUP. our child # processes like ssh will be killed properly, without affecting # unrelated processes. os.setpgid(0, 0) # change random state otherwise forked request handlers would have a # same state inherited from parent. random.seed() def _serverequest(ui, repo, conn, createcmdserver): fin = conn.makefile('rb') fout = conn.makefile('wb') sv = None try: sv = createcmdserver(repo, conn, fin, fout) try: sv.serve() # handle exceptions that may be raised by command server. most of # known exceptions are caught by dispatch. except error.Abort as inst: ui.warn(_('abort: %s\n') % inst) except IOError as inst: if inst.errno != errno.EPIPE: raise except KeyboardInterrupt: pass finally: sv.cleanup() except: # re-raises # also write traceback to error channel. otherwise client cannot # see it because it is written to server's stderr by default. if sv: cerr = sv.cerr else: cerr = channeledoutput(fout, 'e') traceback.print_exc(file=cerr) raise finally: fin.close() try: fout.close() # implicit flush() may cause another EPIPE except IOError as inst: if inst.errno != errno.EPIPE: raise class unixservicehandler(object): """Set of pluggable operations for unix-mode services Almost all methods except for createcmdserver() are called in the main process. You can't pass mutable resource back from createcmdserver(). """ pollinterval = None def __init__(self, ui): self.ui = ui def bindsocket(self, sock, address): util.bindunixsocket(sock, address) def unlinksocket(self, address): os.unlink(address) def printbanner(self, address): self.ui.status(_('listening at %s\n') % address) self.ui.flush() # avoid buffering of status message def shouldexit(self): """True if server should shut down; checked per pollinterval""" return False def newconnection(self): """Called when main process notices new connection""" pass def createcmdserver(self, repo, conn, fin, fout): """Create new command server instance; called in the process that serves for the current connection""" return server(self.ui, repo, fin, fout) class unixforkingservice(object): """ Listens on unix domain socket and forks server per connection """ def __init__(self, ui, repo, opts, handler=None): self.ui = ui self.repo = repo self.address = opts['address'] if not util.safehasattr(socket, 'AF_UNIX'): raise error.Abort(_('unsupported platform')) if not self.address: raise error.Abort(_('no socket path specified with --address')) self._servicehandler = handler or unixservicehandler(ui) self._sock = None self._oldsigchldhandler = None self._workerpids = set() # updated by signal handler; do not iterate def init(self): self._sock = socket.socket(socket.AF_UNIX) self._servicehandler.bindsocket(self._sock, self.address) self._sock.listen(socket.SOMAXCONN) o = signal.signal(signal.SIGCHLD, self._sigchldhandler) self._oldsigchldhandler = o self._servicehandler.printbanner(self.address) def _cleanup(self): signal.signal(signal.SIGCHLD, self._oldsigchldhandler) self._sock.close() self._servicehandler.unlinksocket(self.address) # don't kill child processes as they have active clients, just wait self._reapworkers(0) def run(self): try: self._mainloop() finally: self._cleanup() def _mainloop(self): h = self._servicehandler while not h.shouldexit(): try: ready = select.select([self._sock], [], [], h.pollinterval)[0] if not ready: continue conn, _addr = self._sock.accept() except (select.error, socket.error) as inst: if inst.args[0] == errno.EINTR: continue raise pid = os.fork() if pid: try: self.ui.debug('forked worker process (pid=%d)\n' % pid) self._workerpids.add(pid) h.newconnection() finally: conn.close() # release handle in parent process else: try: self._runworker(conn) conn.close() os._exit(0) except: # never return, hence no re-raises try: self.ui.traceback(force=True) finally: os._exit(255) def _sigchldhandler(self, signal, frame): self._reapworkers(os.WNOHANG) def _reapworkers(self, options): while self._workerpids: try: pid, _status = os.waitpid(-1, options) except OSError as inst: if inst.errno == errno.EINTR: continue if inst.errno != errno.ECHILD: raise # no child processes at all (reaped by other waitpid()?) self._workerpids.clear() return if pid == 0: # no waitable child processes return self.ui.debug('worker process exited (pid=%d)\n' % pid) self._workerpids.discard(pid) def _runworker(self, conn): signal.signal(signal.SIGCHLD, self._oldsigchldhandler) _initworkerprocess() h = self._servicehandler try: _serverequest(self.ui, self.repo, conn, h.createcmdserver) finally: gc.collect() # trigger __del__ since worker process uses os._exit _servicemap = { 'pipe': pipeservice, 'unix': unixforkingservice, } def createservice(ui, repo, opts): mode = opts['cmdserver'] try: return _servicemap[mode](ui, repo, opts) except KeyError: raise error.Abort(_('unknown mode %s') % mode)