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view tests/test-push-cgi.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 | 23b749b84b8a |
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#require no-msys # MSYS will translate web paths as if they were file paths This is a test of the push wire protocol over CGI-based hgweb. initialize repository $ hg init r $ cd r $ echo a > a $ hg ci -A -m "0" adding a $ echo '[web]' > .hg/hgrc $ echo 'allow_push = *' >> .hg/hgrc $ echo 'push_ssl = false' >> .hg/hgrc create hgweb invocation script $ cat >hgweb.cgi <<HGWEB > import cgitb > cgitb.enable() > from mercurial import demandimport; demandimport.enable() > from mercurial.hgweb import hgweb > from mercurial.hgweb import wsgicgi > application = hgweb('.', 'test repository') > wsgicgi.launch(application) > HGWEB $ chmod 755 hgweb.cgi test preparation $ . "$TESTDIR/cgienv" $ REQUEST_METHOD="POST"; export REQUEST_METHOD $ CONTENT_TYPE="application/octet-stream"; export CONTENT_TYPE $ hg bundle --type v1 --all bundle.hg 1 changesets found $ CONTENT_LENGTH=279; export CONTENT_LENGTH; expect failure because heads doesn't match (formerly known as 'unsynced changes') $ QUERY_STRING="cmd=unbundle&heads=0000000000000000000000000000000000000000"; export QUERY_STRING $ $PYTHON hgweb.cgi <bundle.hg >page1 2>&1 $ cat page1 Status: 200 Script output follows\r (esc) Content-Type: application/mercurial-0.1\r (esc) Content-Length: 64\r (esc) \r (esc) 0 repository changed while preparing changes - please try again successful force push $ QUERY_STRING="cmd=unbundle&heads=666f726365"; export QUERY_STRING $ $PYTHON hgweb.cgi <bundle.hg >page2 2>&1 $ cat page2 Status: 200 Script output follows\r (esc) Content-Type: application/mercurial-0.1\r (esc) Content-Length: 102\r (esc) \r (esc) 1 adding changesets adding manifests adding file changes added 0 changesets with 0 changes to 1 files successful push, list of heads $ QUERY_STRING="cmd=unbundle&heads=f7b1eb17ad24730a1651fccd46c43826d1bbc2ac"; export QUERY_STRING $ $PYTHON hgweb.cgi <bundle.hg >page3 2>&1 $ cat page3 Status: 200 Script output follows\r (esc) Content-Type: application/mercurial-0.1\r (esc) Content-Length: 102\r (esc) \r (esc) 1 adding changesets adding manifests adding file changes added 0 changesets with 0 changes to 1 files successful push, SHA1 hash of heads (unbundlehash capability) $ QUERY_STRING="cmd=unbundle&heads=686173686564 5a785a5f9e0d433b88ed862b206b011b0c3a9d13"; export QUERY_STRING $ $PYTHON hgweb.cgi <bundle.hg >page4 2>&1 $ cat page4 Status: 200 Script output follows\r (esc) Content-Type: application/mercurial-0.1\r (esc) Content-Length: 102\r (esc) \r (esc) 1 adding changesets adding manifests adding file changes added 0 changesets with 0 changes to 1 files $ cd ..