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view tests/wireprotohelpers.sh @ 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 | b4d85bc122bd |
children | b3c6c194f33a |
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HTTPV2=exp-http-v2-0001 MEDIATYPE=application/mercurial-exp-framing-0005 sendhttpraw() { hg --verbose debugwireproto --peer raw http://$LOCALIP:$HGPORT/ } sendhttpv2peer() { hg --verbose debugwireproto --nologhandshake --peer http2 http://$LOCALIP:$HGPORT/ } sendhttpv2peerhandshake() { hg --verbose debugwireproto --peer http2 http://$LOCALIP:$HGPORT/ } cat > dummycommands.py << EOF from mercurial import ( wireprototypes, wireprotov1server, wireprotov2server, ) @wireprotov1server.wireprotocommand('customreadonly', permission='pull') def customreadonlyv1(repo, proto): return wireprototypes.bytesresponse(b'customreadonly bytes response') @wireprotov2server.wireprotocommand('customreadonly', permission='pull') def customreadonlyv2(repo, proto): return wireprototypes.cborresponse(b'customreadonly bytes response') @wireprotov1server.wireprotocommand('customreadwrite', permission='push') def customreadwrite(repo, proto): return wireprototypes.bytesresponse(b'customreadwrite bytes response') @wireprotov2server.wireprotocommand('customreadwrite', permission='push') def customreadwritev2(repo, proto): return wireprototypes.cborresponse(b'customreadwrite bytes response') EOF cat >> $HGRCPATH << EOF [extensions] drawdag = $TESTDIR/drawdag.py EOF enabledummycommands() { cat >> $HGRCPATH << EOF [extensions] dummycommands = $TESTTMP/dummycommands.py EOF } enablehttpv2() { cat >> $1/.hg/hgrc << EOF [experimental] web.apiserver = true web.api.http-v2 = true EOF }