Mercurial > hg
view tests/test-mq-missingfiles.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 | 34afe92e3719 |
children | 5abc47d4ca6b |
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Issue835: qpush fails immediately when patching a missing file, but remaining added files are still created empty which will trick a future qrefresh. $ cat > writelines.py <<EOF > import sys > path = sys.argv[1] > args = sys.argv[2:] > assert (len(args) % 2) == 0 > > f = open(path, 'wb') > for i in range(len(args) // 2): > count, s = args[2*i:2*i+2] > count = int(count) > s = s.decode('string_escape') > f.write(s*count) > f.close() > EOF $ echo "[extensions]" >> $HGRCPATH $ echo "mq=" >> $HGRCPATH $ hg init normal $ cd normal $ $PYTHON ../writelines.py b 10 'a\n' $ hg ci -Am addb adding b $ echo a > a $ $PYTHON ../writelines.py b 2 'b\n' 10 'a\n' 2 'c\n' $ echo c > c $ hg add a c $ hg qnew -f changeb $ hg qpop popping changeb patch queue now empty $ hg rm b $ hg ci -Am rmb Push patch with missing target: $ hg qpush applying changeb unable to find 'b' for patching (use '--prefix' to apply patch relative to the current directory) 2 out of 2 hunks FAILED -- saving rejects to file b.rej patch failed, unable to continue (try -v) patch failed, rejects left in working directory errors during apply, please fix and qrefresh changeb [2] Display added files: $ cat a a $ cat c c Display rejections: $ cat b.rej --- b +++ b @@ -1,3 +1,5 @@ +b +b a a a @@ -8,3 +10,5 @@ a a a +c +c Test missing renamed file $ hg qpop popping changeb patch queue now empty $ hg up -qC 0 $ echo a > a $ hg mv b bb $ $PYTHON ../writelines.py bb 2 'b\n' 10 'a\n' 2 'c\n' $ echo c > c $ hg add a c $ hg qnew changebb $ hg qpop popping changebb patch queue now empty $ hg up -qC 1 $ hg qpush applying changebb patching file bb Hunk #1 FAILED at 0 Hunk #2 FAILED at 7 2 out of 2 hunks FAILED -- saving rejects to file bb.rej b not tracked! patch failed, unable to continue (try -v) patch failed, rejects left in working directory errors during apply, please fix and qrefresh changebb [2] $ cat a a $ cat c c $ cat bb.rej --- bb +++ bb @@ -1,3 +1,5 @@ +b +b a a a @@ -8,3 +10,5 @@ a a a +c +c $ cd .. $ echo "[diff]" >> $HGRCPATH $ echo "git=1" >> $HGRCPATH $ hg init git $ cd git $ $PYTHON ../writelines.py b 1 '\x00' $ hg ci -Am addb adding b $ echo a > a $ $PYTHON ../writelines.py b 1 '\x01' 1 '\x00' $ echo c > c $ hg add a c $ hg qnew -f changeb $ hg qpop popping changeb patch queue now empty $ hg rm b $ hg ci -Am rmb Push git patch with missing target: $ hg qpush applying changeb unable to find 'b' for patching (use '--prefix' to apply patch relative to the current directory) 1 out of 1 hunks FAILED -- saving rejects to file b.rej patch failed, unable to continue (try -v) patch failed, rejects left in working directory errors during apply, please fix and qrefresh changeb [2] $ hg st ? b.rej Display added files: $ cat a a $ cat c c Display rejections: $ cat b.rej --- b +++ b GIT binary patch literal 2 Jc${No0000400IC2 $ cd .. Test push creating directory during git copy or rename: $ hg init missingdir $ cd missingdir $ echo a > a $ hg ci -Am adda adding a $ mkdir d $ hg copy a d/a2 $ hg mv a d/a $ hg qnew -g -f patch $ hg qpop popping patch patch queue now empty $ hg qpush applying patch now at: patch $ cd ..