Mercurial > hg
view tests/test-editor-filename.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 | 4bf1889456f3 |
children | f802a75da585 |
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Test temp file used with an editor has the expected suffix. $ hg init Create an editor that writes its arguments to stdout and set it to $HGEDITOR. $ cat > editor.sh << EOF > echo "\$@" > exit 1 > EOF $ hg add editor.sh $ HGEDITOR="sh $TESTTMP/editor.sh" $ export HGEDITOR Verify that the path for a commit editor has the expected suffix. $ hg commit *.commit.hg.txt (glob) abort: edit failed: sh exited with status 1 [255] Verify that the path for a histedit editor has the expected suffix. $ cat >> $HGRCPATH <<EOF > [extensions] > rebase= > histedit= > EOF $ hg commit --message 'At least one commit for histedit.' $ hg histedit *.histedit.hg.txt (glob) abort: edit failed: sh exited with status 1 [255] Verify that when performing an action that has the side-effect of creating an editor for a diff, the file ends in .diff. $ echo 1 > one $ echo 2 > two $ hg add adding one adding two $ hg commit --interactive --config ui.interactive=true --config ui.interface=text << EOF > y > e > q > EOF diff --git a/one b/one new file mode 100644 examine changes to 'one'? [Ynesfdaq?] y @@ -0,0 +1,1 @@ +1 record change 1/2 to 'one'? [Ynesfdaq?] e *.diff (glob) editor exited with exit code 1 record change 1/2 to 'one'? [Ynesfdaq?] q abort: user quit [255]