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view mercurial/httpconnection.py @ 38732:be4984261611
merge: mark file gets as not thread safe (issue5933)
In default installs, this has the effect of disabling the thread-based
worker on Windows when manifesting files in the working directory. My
measurements have shown that with revlog-based repositories, Mercurial
spends a lot of CPU time in revlog code resolving file data. This ends
up incurring a lot of context switching across threads and slows down
`hg update` operations when going from an empty working directory to
the tip of the repo.
On mozilla-unified (246,351 files) on an i7-6700K (4+4 CPUs):
before: 487s wall
after: 360s wall (equivalent to worker.enabled=false)
cpus=2: 379s wall
Even with only 2 threads, the thread pool is still slower.
The introduction of the thread-based worker (02b36e860e0b) states that
it resulted in a "~50%" speedup for `hg sparse --enable-profile` and
`hg sparse --disable-profile`. This disagrees with my measurement
above. I theorize a few reasons for this:
1) Removal of files from the working directory is I/O - not CPU - bound
and should benefit from a thread pool (unless I/O is insanely fast
and the GIL release is near instantaneous). So tests like `hg sparse
--enable-profile` may exercise deletion throughput and aren't good
benchmarks for worker tasks that are CPU heavy.
2) The patch was authored by someone at Facebook. The results were
likely measured against a repository using remotefilelog. And I
believe that revision retrieval during working directory updates with
remotefilelog will often use a remote store, thus being I/O and not
CPU bound. This probably resulted in an overstated performance gain.
Since there appears to be a need to enable the thread-based worker with
some stores, I've made the flagging of file gets as thread safe
configurable. I've made it experimental because I don't want to formalize
a boolean flag for this option and because this attribute is best
captured against the store implementation. But we don't have a proper
store API for this yet. I'd rather cross this bridge later.
It is possible there are revlog-based repositories that do benefit from
a thread-based worker. I didn't do very comprehensive testing. If there
are, we may want to devise a more proper algorithm for whether to use
the thread-based worker, including possibly config options to limit the
number of threads to use. But until I see evidence that justifies
complexity, simplicity wins.
Differential Revision: https://phab.mercurial-scm.org/D3963
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 18 Jul 2018 09:49:34 -0700 |
parents | 5f9d436cd3b7 |
children | c53f0ead5781 |
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# httpconnection.py - urllib2 handler for new http support # # Copyright 2005, 2006, 2007, 2008 Matt Mackall <mpm@selenic.com> # Copyright 2006, 2007 Alexis S. L. Carvalho <alexis@cecm.usp.br> # Copyright 2006 Vadim Gelfer <vadim.gelfer@gmail.com> # Copyright 2011 Google, Inc. # # 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 os from .i18n import _ from . import ( pycompat, util, ) urlerr = util.urlerr urlreq = util.urlreq # moved here from url.py to avoid a cycle class httpsendfile(object): """This is a wrapper around the objects returned by python's "open". Its purpose is to send file-like objects via HTTP. It do however not define a __len__ attribute because the length might be more than Py_ssize_t can handle. """ def __init__(self, ui, *args, **kwargs): self.ui = ui self._data = open(*args, **kwargs) self.seek = self._data.seek self.close = self._data.close self.write = self._data.write self.length = os.fstat(self._data.fileno()).st_size self._pos = 0 # We pass double the max for total because we currently have # to send the bundle twice in the case of a server that # requires authentication. Since we can't know until we try # once whether authentication will be required, just lie to # the user and maybe the push succeeds suddenly at 50%. self._progress = ui.makeprogress(_('sending'), unit=_('kb'), total=(self.length // 1024 * 2)) def read(self, *args, **kwargs): ret = self._data.read(*args, **kwargs) if not ret: self._progress.complete() return ret self._pos += len(ret) self._progress.update(self._pos // 1024) return ret def __enter__(self): return self def __exit__(self, exc_type, exc_val, exc_tb): self.close() # moved here from url.py to avoid a cycle def readauthforuri(ui, uri, user): uri = pycompat.bytesurl(uri) # Read configuration groups = {} for key, val in ui.configitems('auth'): if key in ('cookiefile',): continue if '.' not in key: ui.warn(_("ignoring invalid [auth] key '%s'\n") % key) continue group, setting = key.rsplit('.', 1) gdict = groups.setdefault(group, {}) if setting in ('username', 'cert', 'key'): val = util.expandpath(val) gdict[setting] = val # Find the best match scheme, hostpath = uri.split('://', 1) bestuser = None bestlen = 0 bestauth = None for group, auth in groups.iteritems(): if user and user != auth.get('username', user): # If a username was set in the URI, the entry username # must either match it or be unset continue prefix = auth.get('prefix') if not prefix: continue p = prefix.split('://', 1) if len(p) > 1: schemes, prefix = [p[0]], p[1] else: schemes = (auth.get('schemes') or 'https').split() if (prefix == '*' or hostpath.startswith(prefix)) and \ (len(prefix) > bestlen or (len(prefix) == bestlen and \ not bestuser and 'username' in auth)) \ and scheme in schemes: bestlen = len(prefix) bestauth = group, auth bestuser = auth.get('username') if user and not bestuser: auth['username'] = user return bestauth