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view tests/test-newcgi.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 | 8e6f4939a69a |
children | 5abc47d4ca6b |
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#require no-msys # MSYS will translate web paths as if they were file paths This tests if CGI files from after d0db3462d568 but before d74fc8dec2b4 still work. $ hg init test $ cat >hgweb.cgi <<HGWEB > #!$PYTHON > # > # An example CGI script to use hgweb, edit as necessary > > import cgitb > cgitb.enable() > > from mercurial import demandimport; demandimport.enable() > from mercurial.hgweb import hgweb > from mercurial.hgweb import wsgicgi > from mercurial.hgweb.request import wsgiapplication > > def make_web_app(): > return hgweb("test", "Empty test repository") > > wsgicgi.launch(wsgiapplication(make_web_app)) > HGWEB $ chmod 755 hgweb.cgi $ cat >hgweb.config <<HGWEBDIRCONF > [paths] > test = test > HGWEBDIRCONF $ cat >hgwebdir.cgi <<HGWEBDIR > #!$PYTHON > # > # An example CGI script to export multiple hgweb repos, edit as necessary > > import cgitb > cgitb.enable() > > from mercurial import demandimport; demandimport.enable() > from mercurial.hgweb import hgwebdir > from mercurial.hgweb import wsgicgi > from mercurial.hgweb.request import wsgiapplication > > def make_web_app(): > return hgwebdir("hgweb.config") > > wsgicgi.launch(wsgiapplication(make_web_app)) > HGWEBDIR $ chmod 755 hgwebdir.cgi $ . "$TESTDIR/cgienv" $ $PYTHON hgweb.cgi > page1 $ $PYTHON hgwebdir.cgi > page2 $ PATH_INFO="/test/" $ PATH_TRANSLATED="/var/something/test.cgi" $ REQUEST_URI="/test/test/" $ SCRIPT_URI="http://hg.omnifarious.org/test/test/" $ SCRIPT_URL="/test/test/" $ $PYTHON hgwebdir.cgi > page3 $ grep -i error page1 page2 page3 [1]