view tests/test-diff-upgrade.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

#require execbit

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > autodiff = $TESTDIR/autodiff.py
  > [diff]
  > nodates = 1
  > EOF

  $ hg init repo
  $ cd repo



make a combination of new, changed and deleted file

  $ echo regular > regular
  $ echo rmregular > rmregular
  $ $PYTHON -c "open('bintoregular', 'wb').write(b'\0')"
  $ touch rmempty
  $ echo exec > exec
  $ chmod +x exec
  $ echo rmexec > rmexec
  $ chmod +x rmexec
  $ echo setexec > setexec
  $ echo unsetexec > unsetexec
  $ chmod +x unsetexec
  $ echo binary > binary
  $ $PYTHON -c "open('rmbinary', 'wb').write(b'\0')"
  $ hg ci -Am addfiles
  adding binary
  adding bintoregular
  adding exec
  adding regular
  adding rmbinary
  adding rmempty
  adding rmexec
  adding rmregular
  adding setexec
  adding unsetexec
  $ echo regular >> regular
  $ echo newregular >> newregular
  $ rm rmempty
  $ touch newempty
  $ rm rmregular
  $ echo exec >> exec
  $ echo newexec > newexec
  $ echo bintoregular > bintoregular
  $ chmod +x newexec
  $ rm rmexec
  $ chmod +x setexec
  $ chmod -x unsetexec
  $ $PYTHON -c "open('binary', 'wb').write(b'\0\0')"
  $ $PYTHON -c "open('newbinary', 'wb').write(b'\0')"
  $ rm rmbinary
  $ hg addremove -s 0
  adding newbinary
  adding newempty
  adding newexec
  adding newregular
  removing rmbinary
  removing rmempty
  removing rmexec
  removing rmregular

git=no: regular diff for all files

  $ hg autodiff --git=no
  diff -r a66d19b9302d binary
  Binary file binary has changed
  diff -r a66d19b9302d bintoregular
  Binary file bintoregular has changed
  diff -r a66d19b9302d exec
  --- a/exec
  +++ b/exec
  @@ -1,1 +1,2 @@
   exec
  +exec
  diff -r a66d19b9302d newbinary
  Binary file newbinary has changed
  diff -r a66d19b9302d newexec
  --- /dev/null
  +++ b/newexec
  @@ -0,0 +1,1 @@
  +newexec
  diff -r a66d19b9302d newregular
  --- /dev/null
  +++ b/newregular
  @@ -0,0 +1,1 @@
  +newregular
  diff -r a66d19b9302d regular
  --- a/regular
  +++ b/regular
  @@ -1,1 +1,2 @@
   regular
  +regular
  diff -r a66d19b9302d rmbinary
  Binary file rmbinary has changed
  diff -r a66d19b9302d rmexec
  --- a/rmexec
  +++ /dev/null
  @@ -1,1 +0,0 @@
  -rmexec
  diff -r a66d19b9302d rmregular
  --- a/rmregular
  +++ /dev/null
  @@ -1,1 +0,0 @@
  -rmregular

git=yes: git diff for single regular file

  $ hg autodiff --git=yes regular
  diff --git a/regular b/regular
  --- a/regular
  +++ b/regular
  @@ -1,1 +1,2 @@
   regular
  +regular

git=auto: regular diff for regular files and non-binary removals

  $ hg autodiff --git=auto regular newregular rmregular rmexec
  diff -r a66d19b9302d newregular
  --- /dev/null
  +++ b/newregular
  @@ -0,0 +1,1 @@
  +newregular
  diff -r a66d19b9302d regular
  --- a/regular
  +++ b/regular
  @@ -1,1 +1,2 @@
   regular
  +regular
  diff -r a66d19b9302d rmexec
  --- a/rmexec
  +++ /dev/null
  @@ -1,1 +0,0 @@
  -rmexec
  diff -r a66d19b9302d rmregular
  --- a/rmregular
  +++ /dev/null
  @@ -1,1 +0,0 @@
  -rmregular

  $ for f in exec newexec setexec unsetexec binary newbinary newempty rmempty rmbinary bintoregular; do
  >     echo
  >     echo '% git=auto: git diff for' $f
  >     hg autodiff --git=auto $f
  > done
  
  % git=auto: git diff for exec
  diff -r a66d19b9302d exec
  --- a/exec
  +++ b/exec
  @@ -1,1 +1,2 @@
   exec
  +exec
  
  % git=auto: git diff for newexec
  diff --git a/newexec b/newexec
  new file mode 100755
  --- /dev/null
  +++ b/newexec
  @@ -0,0 +1,1 @@
  +newexec
  
  % git=auto: git diff for setexec
  diff --git a/setexec b/setexec
  old mode 100644
  new mode 100755
  
  % git=auto: git diff for unsetexec
  diff --git a/unsetexec b/unsetexec
  old mode 100755
  new mode 100644
  
  % git=auto: git diff for binary
  diff --git a/binary b/binary
  index a9128c283485202893f5af379dd9beccb6e79486..09f370e38f498a462e1ca0faa724559b6630c04f
  GIT binary patch
  literal 2
  Jc${Nk0000200961
  
  
  % git=auto: git diff for newbinary
  diff --git a/newbinary b/newbinary
  new file mode 100644
  index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..f76dd238ade08917e6712764a16a22005a50573d
  GIT binary patch
  literal 1
  Ic${MZ000310RR91
  
  
  % git=auto: git diff for newempty
  diff --git a/newempty b/newempty
  new file mode 100644
  
  % git=auto: git diff for rmempty
  diff --git a/rmempty b/rmempty
  deleted file mode 100644
  
  % git=auto: git diff for rmbinary
  diff --git a/rmbinary b/rmbinary
  deleted file mode 100644
  index f76dd238ade08917e6712764a16a22005a50573d..e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
  GIT binary patch
  literal 0
  Hc$@<O00001
  
  
  % git=auto: git diff for bintoregular
  diff --git a/bintoregular b/bintoregular
  index f76dd238ade08917e6712764a16a22005a50573d..9c42f2b6427d8bf034b7bc23986152dc01bfd3ab
  GIT binary patch
  literal 13
  Uc$`bh%qz(+N=+}#Ni5<5043uE82|tP
  


git=warn: regular diff with data loss warnings

  $ hg autodiff --git=warn
  diff -r a66d19b9302d binary
  Binary file binary has changed
  diff -r a66d19b9302d bintoregular
  Binary file bintoregular has changed
  diff -r a66d19b9302d exec
  --- a/exec
  +++ b/exec
  @@ -1,1 +1,2 @@
   exec
  +exec
  diff -r a66d19b9302d newbinary
  Binary file newbinary has changed
  diff -r a66d19b9302d newexec
  --- /dev/null
  +++ b/newexec
  @@ -0,0 +1,1 @@
  +newexec
  diff -r a66d19b9302d newregular
  --- /dev/null
  +++ b/newregular
  @@ -0,0 +1,1 @@
  +newregular
  diff -r a66d19b9302d regular
  --- a/regular
  +++ b/regular
  @@ -1,1 +1,2 @@
   regular
  +regular
  diff -r a66d19b9302d rmbinary
  Binary file rmbinary has changed
  diff -r a66d19b9302d rmexec
  --- a/rmexec
  +++ /dev/null
  @@ -1,1 +0,0 @@
  -rmexec
  diff -r a66d19b9302d rmregular
  --- a/rmregular
  +++ /dev/null
  @@ -1,1 +0,0 @@
  -rmregular
  data lost for: binary
  data lost for: bintoregular
  data lost for: newbinary
  data lost for: newempty
  data lost for: newexec
  data lost for: rmbinary
  data lost for: rmempty
  data lost for: setexec
  data lost for: unsetexec

git=abort: fail on execute bit change

  $ hg autodiff --git=abort regular setexec
  abort: losing data for setexec
  [255]

git=abort: succeed on regular file

  $ hg autodiff --git=abort regular
  diff -r a66d19b9302d regular
  --- a/regular
  +++ b/regular
  @@ -1,1 +1,2 @@
   regular
  +regular

  $ cd ..