tests/test-profile.t

encoding: fix trim() to be O(n) instead of O(n^2)

`encoding.trim()` iterated over the possible lengths smaller than the
input and created a slice for each. It then calculated the column
width of the result, which is of course O(n), so the overall algorithm
was O(n). This patch rewrites it to iterate over the unicode
characters, keeping track of the length so far. Also, the old
algorithm started from the end of the string, which made it much worse
when the input is large and the limit is small (such as the typical 72
we pass to it).

You can time it by running something like this:

```
time python3 -c 'from mercurial.utils import stringutil; print(stringutil.ellipsis(b"0123456789" * 1000, 5))'
```

That drops from 4.05 s to 83 ms with this patch (and most of that is
of course startup time).

Differential Revision: https://phab.mercurial-scm.org/D12089

test --time

  $ hg --time help -q help 2>&1 | grep time > /dev/null
  $ hg init a
  $ cd a

Function to check that statprof ran
  $ statprofran () {
  >   egrep 'Sample count:|No samples recorded' > /dev/null
  > }

test --profile

  $ hg st --profile 2>&1 | statprofran

Abreviated version

  $ hg st --prof 2>&1 | statprofran

In alias

  $ hg --config "alias.profst=status --profile" profst 2>&1 | statprofran

#if lsprof

  $ prof () {
  >   hg --config profiling.type=ls --profile $@
  > }

  $ prof st 2>../out
  $ grep CallCount ../out > /dev/null || cat ../out

  $ prof --config profiling.output=../out st
  $ grep CallCount ../out > /dev/null || cat ../out

  $ prof --config profiling.output=blackbox --config extensions.blackbox= st
  $ grep CallCount .hg/blackbox.log > /dev/null || cat .hg/blackbox.log

  $ prof --config profiling.format=text st 2>../out
  $ grep CallCount ../out > /dev/null || cat ../out

  $ echo "[profiling]" >> $HGRCPATH
  $ echo "format=kcachegrind" >> $HGRCPATH

  $ prof st 2>../out
  $ grep 'events: Ticks' ../out > /dev/null || cat ../out

  $ prof --config profiling.output=../out st
  $ grep 'events: Ticks' ../out > /dev/null || cat ../out

#endif

#if lsprof serve

Profiling of HTTP requests works

  $ prof --config profiling.format=text --config profiling.output=../profile.log serve -d -p $HGPORT --pid-file ../hg.pid -A ../access.log
  $ cat ../hg.pid >> $DAEMON_PIDS
  $ hg -q clone -U http://localhost:$HGPORT ../clone

A single profile is logged because file logging doesn't append
  $ grep CallCount ../profile.log | wc -l
  \s*1 (re)

#endif

Install an extension that can sleep and guarantee a profiler has time to run

  $ cat >> sleepext_with_a_long_filename.py << EOF
  > import time
  > from mercurial import registrar
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > @command(b'sleep', [], b'hg sleep')
  > def sleep_for_at_least_one_stat_cycle(ui, *args, **kwargs):
  >     t = time.time()  # don't use time.sleep because we need CPU time
  >     while time.time() - t < 0.5:
  >         pass
  > EOF

  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > sleep = `pwd`/sleepext_with_a_long_filename.py
  > EOF

statistical profiler works

  $ hg --profile sleep 2>../out
  $ cat ../out | statprofran

Various statprof formatters work

  $ hg --profile --config profiling.statformat=byline sleep 2>../out || cat ../out
  $ grep -v _path_stat ../out | head -n 3
    %   cumulative      self          
   time    seconds   seconds  name    
  * sleepext_with_a_long_filename.py:*:sleep_for_at_least_one_stat_cycle (glob)
  $ cat ../out | statprofran

  $ hg --profile --config profiling.statformat=bymethod sleep 2>../out || cat ../out
  $ head -n 1 ../out
    %   cumulative      self          
  $ cat ../out | statprofran

Windows real time tracking is broken, only use CPU

#if no-windows
  $ hg --profile --config profiling.time-track=real --config profiling.statformat=hotpath sleep 2>../out || cat ../out
  $ cat ../out | statprofran
  $ grep sleepext_with_a_long_filename.py ../out | head -n 1
  .* [0-9.]+%  [0-9.]+s  sleepext_with_a_long_filename.py:\s*sleep_for_at_least_one_stat_cycle, line \d+:\s+(while|pass).* (re)
#endif

  $ hg --profile --config profiling.time-track=cpu --config profiling.statformat=hotpath sleep 2>../out || cat ../out
  $ cat ../out | statprofran
  $ grep sleepext_with_a_long_filename.py ../out | head -n 1
  .* [0-9.]+%  [0-9.]+s  sleepext_with_a_long_filename.py:\s*sleep_for_at_least_one_stat_cycle, line \d+:\s+(while|pass).* (re)

  $ hg --profile --config profiling.statformat=json sleep 2>../out || cat ../out
  $ cat ../out
  \[\[-?\d+.* (re)

statprof can be used as a standalone module

  $ "$PYTHON" -m mercurial.statprof hotpath
  must specify --file to load
  [1]

  $ cd ..

#if no-chg
profiler extension could be loaded before other extensions

  $ cat > fooprof.py <<EOF
  > from __future__ import absolute_import
  > import contextlib
  > import sys
  > @contextlib.contextmanager
  > def profile(ui, fp):
  >     print('fooprof: start profile')
  >     sys.stdout.flush()
  >     yield
  >     print('fooprof: end profile')
  >     sys.stdout.flush()
  > def extsetup(ui):
  >     ui.write(b'fooprof: loaded\n')
  > EOF

  $ cat > otherextension.py <<EOF
  > from __future__ import absolute_import
  > def extsetup(ui):
  >     ui.write(b'otherextension: loaded\n')
  > EOF

  $ hg init b
  $ cd b
  $ cat >> .hg/hgrc <<EOF
  > [extensions]
  > other = $TESTTMP/otherextension.py
  > fooprof = $TESTTMP/fooprof.py
  > EOF

  $ hg root
  otherextension: loaded
  fooprof: loaded
  $TESTTMP/b
  $ HGPROF=fooprof hg root --profile
  fooprof: loaded
  fooprof: start profile
  otherextension: loaded
  $TESTTMP/b
  fooprof: end profile

  $ HGPROF=other hg root --profile 2>&1 | head -n 2
  otherextension: loaded
  unrecognized profiler 'other' - ignored

  $ HGPROF=unknown hg root --profile 2>&1 | head -n 1
  unrecognized profiler 'unknown' - ignored

  $ cd ..
#endif