Mercurial > hg
view tests/get-with-headers.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> |
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date | Wed, 18 Jul 2018 09:49:34 -0700 |
parents | cfd0c1df5e33 |
children | fe11fc7e541f |
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#!/usr/bin/env python """This does HTTP GET requests given a host:port and path and returns a subset of the headers plus the body of the result.""" from __future__ import absolute_import import argparse import json import os import sys from mercurial import ( util, ) httplib = util.httplib try: import msvcrt msvcrt.setmode(sys.stdout.fileno(), os.O_BINARY) msvcrt.setmode(sys.stderr.fileno(), os.O_BINARY) except ImportError: pass stdout = getattr(sys.stdout, 'buffer', sys.stdout) parser = argparse.ArgumentParser() parser.add_argument('--twice', action='store_true') parser.add_argument('--headeronly', action='store_true') parser.add_argument('--json', action='store_true') parser.add_argument('--hgproto') parser.add_argument('--requestheader', nargs='*', default=[], help='Send an additional HTTP request header. Argument ' 'value is <header>=<value>') parser.add_argument('--bodyfile', help='Write HTTP response body to a file') parser.add_argument('host') parser.add_argument('path') parser.add_argument('show', nargs='*') args = parser.parse_args() twice = args.twice headeronly = args.headeronly formatjson = args.json hgproto = args.hgproto requestheaders = args.requestheader tag = None def request(host, path, show): assert not path.startswith('/'), path global tag headers = {} if tag: headers['If-None-Match'] = tag if hgproto: headers['X-HgProto-1'] = hgproto for header in requestheaders: key, value = header.split('=', 1) headers[key] = value conn = httplib.HTTPConnection(host) conn.request("GET", '/' + path, None, headers) response = conn.getresponse() stdout.write(b'%d %s\n' % (response.status, response.reason.encode('ascii'))) if show[:1] == ['-']: show = sorted(h for h, v in response.getheaders() if h.lower() not in show) for h in [h.lower() for h in show]: if response.getheader(h, None) is not None: stdout.write(b"%s: %s\n" % (h.encode('ascii'), response.getheader(h).encode('ascii'))) if not headeronly: stdout.write(b'\n') data = response.read() if args.bodyfile: bodyfh = open(args.bodyfile, 'wb') else: bodyfh = stdout # Pretty print JSON. This also has the beneficial side-effect # of verifying emitted JSON is well-formed. if formatjson: # json.dumps() will print trailing newlines. Eliminate them # to make tests easier to write. data = json.loads(data) lines = json.dumps(data, sort_keys=True, indent=2).splitlines() for line in lines: bodyfh.write(line.rstrip()) bodyfh.write(b'\n') else: bodyfh.write(data) if args.bodyfile: bodyfh.close() if twice and response.getheader('ETag', None): tag = response.getheader('ETag') return response.status status = request(args.host, args.path, args.show) if twice: status = request(args.host, args.path, args.show) if 200 <= status <= 305: sys.exit(0) sys.exit(1)