view mercurial/lsprofcalltree.py @ 45390:7d24201b6447

worker: don't expose readinto() on _blockingreader since pickle is picky

The `pickle` module expects the input to be buffered and a whole
object to be available when `pickle.load()` is called, which is not
necessarily true when we send data from workers back to the parent
process (i.e., it seems like a bad assumption for the `pickle` module
to make). We added a workaround for that in
https://phab.mercurial-scm.org/D8076, which made `read()` continue
until all the requested bytes have been read.

As we found out at work after a lot of investigation (I've spent the
last two days on this), the native version of `pickle.load()` has
started calling `readinto()` on the input since Python 3.8. That
started being called in
https://github.com/python/cpython/commit/91f4380cedbae32b49adbea2518014a5624c6523
(and only by the C version of `pickle.load()`)). Before that, it was
only `read()` and `readline()` that were called. The problem with that
was that `readinto()` on our `_blockingreader` was simply delegating
to the underlying, *unbuffered* object. The symptom we saw was that
`hg fix` started failing sometimes on Python 3.8 on Mac. It failed
very relyable in some cases. I still haven't figured out under what
circumstances it fails and I've been unable to reproduce it in test
cases (I've tried writing larger amounts of data, using different
numbers of workers, and making the formatters sleep). I have, however,
been able to reproduce it 3-4 times on Linux, but then it stopped
reproducing on the following few hundred attempts.

To fix the problem, we can simply remove the implementation of
`readinto()`, since the unpickler will then fall back to calling
`read()`. The fallback was added a bit later, in
https://github.com/python/cpython/commit/b19f7ecfa3adc6ba1544225317b9473649815b38. However,
that commit also added checking that what `read()` returns is a
`bytes`, so we also need to convert the `bytearray` we use into
that. I was able to add a test for that failure at least.

Differential Revision: https://phab.mercurial-scm.org/D8928

"""
lsprofcalltree.py - lsprof output which is readable by kcachegrind

Authors:
    * David Allouche <david <at> allouche.net>
    * Jp Calderone & Itamar Shtull-Trauring
    * Johan Dahlin

This software may be used and distributed according to the terms
of the GNU General Public License, incorporated herein by reference.
"""

from __future__ import absolute_import

from . import pycompat


def label(code):
    if isinstance(code, str):
        # built-in functions ('~' sorts at the end)
        return b'~' + pycompat.sysbytes(code)
    else:
        return b'%s %s:%d' % (
            pycompat.sysbytes(code.co_name),
            pycompat.sysbytes(code.co_filename),
            code.co_firstlineno,
        )


class KCacheGrind(object):
    def __init__(self, profiler):
        self.data = profiler.getstats()
        self.out_file = None

    def output(self, out_file):
        self.out_file = out_file
        out_file.write(b'events: Ticks\n')
        self._print_summary()
        for entry in self.data:
            self._entry(entry)

    def _print_summary(self):
        max_cost = 0
        for entry in self.data:
            totaltime = int(entry.totaltime * 1000)
            max_cost = max(max_cost, totaltime)
        self.out_file.write(b'summary: %d\n' % max_cost)

    def _entry(self, entry):
        out_file = self.out_file

        code = entry.code
        if isinstance(code, str):
            out_file.write(b'fi=~\n')
        else:
            out_file.write(b'fi=%s\n' % pycompat.sysbytes(code.co_filename))

        out_file.write(b'fn=%s\n' % label(code))

        inlinetime = int(entry.inlinetime * 1000)
        if isinstance(code, str):
            out_file.write(b'0 %d\n' % inlinetime)
        else:
            out_file.write(b'%d %d\n' % (code.co_firstlineno, inlinetime))

        # recursive calls are counted in entry.calls
        if entry.calls:
            calls = entry.calls
        else:
            calls = []

        if isinstance(code, str):
            lineno = 0
        else:
            lineno = code.co_firstlineno

        for subentry in calls:
            self._subentry(lineno, subentry)

        out_file.write(b'\n')

    def _subentry(self, lineno, subentry):
        out_file = self.out_file
        code = subentry.code
        out_file.write(b'cfn=%s\n' % label(code))
        if isinstance(code, str):
            out_file.write(b'cfi=~\n')
            out_file.write(b'calls=%d 0\n' % subentry.callcount)
        else:
            out_file.write(b'cfi=%s\n' % pycompat.sysbytes(code.co_filename))
            out_file.write(
                b'calls=%d %d\n' % (subentry.callcount, code.co_firstlineno)
            )

        totaltime = int(subentry.totaltime * 1000)
        out_file.write(b'%d %d\n' % (lineno, totaltime))