view tests/test-logtoprocess.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 no-windows

ATTENTION: logtoprocess runs commands asynchronously. Be sure to append "| cat"
to hg commands, to wait for the output, if you want to test its output.
Otherwise the test will be flaky.

Test if logtoprocess correctly captures command-related log calls.

  $ hg init
  $ cat > $TESTTMP/foocommand.py << EOF
  > from __future__ import absolute_import
  > from mercurial import registrar
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > configtable = {}
  > configitem = registrar.configitem(configtable)
  > configitem('logtoprocess', 'foo',
  >     default=None,
  > )
  > @command(b'foo', [])
  > def foo(ui, repo):
  >     ui.log('foo', 'a message: %(bar)s\n', bar='spam')
  > EOF
  $ cp $HGRCPATH $HGRCPATH.bak
  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > logtoprocess=
  > foocommand=$TESTTMP/foocommand.py
  > [logtoprocess]
  > command=echo 'logtoprocess command output:';
  >     echo "\$EVENT";
  >     echo "\$MSG1";
  >     echo "\$MSG2"
  > commandfinish=echo 'logtoprocess commandfinish output:';
  >     echo "\$EVENT";
  >     echo "\$MSG1";
  >     echo "\$MSG2";
  >     echo "\$MSG3"
  > foo=echo 'logtoprocess foo output:';
  >     echo "\$EVENT";
  >     echo "\$MSG1";
  >     echo "\$OPT_BAR"
  > EOF

Running a command triggers both a ui.log('command') and a
ui.log('commandfinish') call. The foo command also uses ui.log.

Use sort to avoid ordering issues between the various processes we spawn:
  $ hg foo | cat | sort
  
  
  
   (chg !)
  0
  a message: spam
  command
  command (chg !)
  commandfinish
  foo
  foo
  foo
  foo
  foo exited 0 after * seconds (glob)
  logtoprocess command output:
  logtoprocess command output: (chg !)
  logtoprocess commandfinish output:
  logtoprocess foo output:
  serve --cmdserver chgunix * (glob) (chg !)
  serve --cmdserver chgunix * (glob) (chg !)
  spam

Confirm that logging blocked time catches stdio properly:
  $ cp $HGRCPATH.bak $HGRCPATH
  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > logtoprocess=
  > pager=
  > [logtoprocess]
  > uiblocked=echo "\$EVENT stdio \$OPT_STDIO_BLOCKED ms command \$OPT_COMMAND_DURATION ms"
  > [ui]
  > logblockedtimes=True
  > EOF

  $ hg log | cat
  uiblocked stdio [0-9]+.[0-9]* ms command [0-9]+.[0-9]* ms (re)