Mercurial > hg
view tests/test-hgweb-non-interactive.t @ 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 | 27fb986e54d0 |
children | c20861b65688 |
line wrap: on
line source
Tests if hgweb can run without touching sys.stdin, as is required by the WSGI standard and strictly implemented by mod_wsgi. $ hg init repo $ cd repo $ echo foo > bar $ hg add bar $ hg commit -m "test" $ cat > request.py <<EOF > from __future__ import absolute_import > import os > import sys > from mercurial import ( > dispatch, > hg, > ui as uimod, > util, > ) > ui = uimod.ui > from mercurial.hgweb.hgweb_mod import ( > hgweb, > ) > stringio = util.stringio > > class FileLike(object): > def __init__(self, real): > self.real = real > def fileno(self): > print >> sys.__stdout__, 'FILENO' > return self.real.fileno() > def read(self): > print >> sys.__stdout__, 'READ' > return self.real.read() > def readline(self): > print >> sys.__stdout__, 'READLINE' > return self.real.readline() > > sys.stdin = FileLike(sys.stdin) > errors = stringio() > input = stringio() > output = stringio() > > def startrsp(status, headers): > print('---- STATUS') > print(status) > print('---- HEADERS') > print([i for i in headers if i[0] != 'ETag']) > print('---- DATA') > return output.write > > env = { > 'wsgi.version': (1, 0), > 'wsgi.url_scheme': 'http', > 'wsgi.errors': errors, > 'wsgi.input': input, > 'wsgi.multithread': False, > 'wsgi.multiprocess': False, > 'wsgi.run_once': False, > 'REQUEST_METHOD': 'GET', > 'SCRIPT_NAME': '', > 'PATH_INFO': '', > 'QUERY_STRING': '', > 'SERVER_NAME': '$LOCALIP', > 'SERVER_PORT': os.environ['HGPORT'], > 'SERVER_PROTOCOL': 'HTTP/1.0' > } > > i = hgweb('.') > for c in i(env, startrsp): > pass > print('---- ERRORS') > print(errors.getvalue()) > print('---- OS.ENVIRON wsgi variables') > print(sorted([x for x in os.environ if x.startswith('wsgi')])) > print('---- request.ENVIRON wsgi variables') > with i._obtainrepo() as repo: > print(sorted([x for x in repo.ui.environ if x.startswith('wsgi')])) > EOF $ $PYTHON request.py ---- STATUS 200 Script output follows ---- HEADERS [('Content-Type', 'text/html; charset=ascii')] ---- DATA ---- ERRORS ---- OS.ENVIRON wsgi variables [] ---- request.ENVIRON wsgi variables ['wsgi.errors', 'wsgi.input', 'wsgi.multiprocess', 'wsgi.multithread', 'wsgi.run_once', 'wsgi.url_scheme', 'wsgi.version'] $ cd ..