Mercurial > hg
view tests/test-extdata.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 | faa41fd282d1 |
children | eec65b706caf |
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$ hg init repo $ cd repo $ for n in 0 1 2 3 4 5 6 7 8 9 10 11; do > echo $n > $n > hg ci -qAm $n > done test revset support $ cat <<'EOF' >> .hg/hgrc > [extdata] > filedata = file:extdata.txt > notes = notes.txt > shelldata = shell:cat extdata.txt | grep 2 > emptygrep = shell:cat extdata.txt | grep empty > EOF $ cat <<'EOF' > extdata.txt > 2 another comment on 2 > 3 > EOF $ cat <<'EOF' > notes.txt > f6ed this change is great! > e834 this is buggy :( > 0625 first post > bogusnode gives no error > a ambiguous node gives no error > EOF $ hg log -qr "extdata(filedata)" 2:f6ed99a58333 3:9de260b1e88e $ hg log -qr "extdata(shelldata)" 2:f6ed99a58333 test weight of extdata() revset $ hg debugrevspec -p optimized "extdata(filedata) & 3" * optimized: (andsmally (func (symbol 'extdata') (symbol 'filedata')) (symbol '3')) 3 test non-zero exit of shell command $ hg log -qr "extdata(emptygrep)" abort: extdata command 'cat extdata.txt | grep empty' failed: exited with status 1 [255] test bad extdata() revset source $ hg log -qr "extdata()" hg: parse error: extdata takes at least 1 string argument [255] $ hg log -qr "extdata(unknown)" abort: unknown extdata source 'unknown' [255] test template support: $ hg log -r:3 -T "{node|short}{if(extdata('notes'), ' # {extdata('notes')}')}\n" 06254b906311 # first post e8342c9a2ed1 # this is buggy :( f6ed99a58333 # this change is great! 9de260b1e88e test template cache: $ hg log -r:3 -T '{rev} "{extdata("notes")}" "{extdata("shelldata")}"\n' 0 "first post" "" 1 "this is buggy :(" "" 2 "this change is great!" "another comment on 2" 3 "" "" test bad extdata() template source $ hg log -T "{extdata()}\n" hg: parse error: extdata expects one argument [255] $ hg log -T "{extdata('unknown')}\n" abort: unknown extdata source 'unknown' [255] $ hg log -T "{extdata(unknown)}\n" hg: parse error: empty data source specified (did you mean extdata('unknown')?) [255] $ hg log -T "{extdata('{unknown}')}\n" hg: parse error: empty data source specified [255] we don't fix up relative file URLs, but we do run shell commands in repo root $ mkdir sub $ cd sub $ hg log -qr "extdata(filedata)" abort: error: $ENOENT$ [255] $ hg log -qr "extdata(shelldata)" 2:f6ed99a58333 $ cd ..