Message-ID: <Y5CREfc21UJqER7G@kernel.org>
Date:   Wed, 7 Dec 2022 10:11:45 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        John Garry <john.g.garry@...cle.com>,
        Sumanth Korikkar <sumanthk@...ux.ibm.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v4] perf jevents: Parse metrics during conversion

Em Tue, Dec 06, 2022 at 10:10:19PM -0800, Ian Rogers escreveu:
> On Tue, Dec 6, 2022 at 9:59 PM Ian Rogers <irogers@...gle.com> wrote:
> >
> > Currently the 'MetricExpr' json value is passed from the json
> > file to the pmu-events.c. This change introduces an expression
> > tree that is parsed into. The parsing is done largely by using
> > operator overloading and python's 'eval' function. Two advantages
> > in doing this are:
> >
> > 1) Broken metrics fail at compile time rather than relying on
> >    `perf test` to detect. `perf test` remains relevant for checking
> >    event encoding and actual metric use.
> >
> > 2) The conversion to a string from the tree can minimize the metric's
> >    string size, for example, preferring 1e6 over 1000000, avoiding
> >    multiplication by 1 and removing unnecessary whitespace. On x86
> >    this reduces the string size by 2,930bytes (0.07%).
> >
> > In future changes it would be possible to programmatically
> > generate the json expressions (a single line of text and so a
> > pain to write manually) for an architecture using the expression
> > tree. This could avoid copy-pasting metrics for all architecture
> > variants.
> >
> > Signed-off-by: Ian Rogers <irogers@...gle.com>
> >
> > v4. Doesn't simplify "0*SLOTS" to 0, as the pattern is used to fix
> >     Intel metrics with topdown events.
> 
> Just noticed Arnaldo took v3:
> https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/commit/?h=tmp.perf/core&id=b4a8116e53023a6d4edc24a3252a845d203dd119
> So I'll post the Intel slots fix separately.

tmp.perf/core stuff can be replaced, I'll replace v3 with v4 there.

Thanks!

- Arnaldo
 
> Thanks,
> Ian
> 
> > v3. Avoids generic types on standard types like set that aren't
> >     supported until Python 3.9, fixing an issue with Python 3.6
> >     reported-by John Garry. v3 also fixes minor pylint issues and adds
> >     a call to Simplify on the read expression tree.
> > v2. Improvements to type information.
> > ---
> >  tools/perf/pmu-events/Build          |   2 +-
> >  tools/perf/pmu-events/jevents.py     |  12 +-
> >  tools/perf/pmu-events/metric.py      | 501 +++++++++++++++++++++++++++
> >  tools/perf/pmu-events/metric_test.py | 153 ++++++++
> >  4 files changed, 664 insertions(+), 4 deletions(-)
> >  create mode 100644 tools/perf/pmu-events/metric.py
> >  create mode 100644 tools/perf/pmu-events/metric_test.py
> >
> > diff --git a/tools/perf/pmu-events/Build b/tools/perf/pmu-events/Build
> > index 04ef95174660..15b9e8fdbffa 100644
> > --- a/tools/perf/pmu-events/Build
> > +++ b/tools/perf/pmu-events/Build
> > @@ -21,7 +21,7 @@ $(OUTPUT)pmu-events/pmu-events.c: pmu-events/empty-pmu-events.c
> >         $(call rule_mkdir)
> >         $(Q)$(call echo-cmd,gen)cp $< $@
> >  else
> > -$(OUTPUT)pmu-events/pmu-events.c: $(JSON) $(JSON_TEST) $(JEVENTS_PY)
> > +$(OUTPUT)pmu-events/pmu-events.c: $(JSON) $(JSON_TEST) $(JEVENTS_PY) pmu-events/metric.py
> >         $(call rule_mkdir)
> >         $(Q)$(call echo-cmd,gen)$(PYTHON) $(JEVENTS_PY) $(JEVENTS_ARCH) pmu-events/arch $@
> >  endif
> > diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py
> > index 0daa3e007528..4c398e0eeb2f 100755
> > --- a/tools/perf/pmu-events/jevents.py
> > +++ b/tools/perf/pmu-events/jevents.py
> > @@ -4,6 +4,7 @@
> >  import argparse
> >  import csv
> >  import json
> > +import metric
> >  import os
> >  import sys
> >  from typing import (Callable, Dict, Optional, Sequence, Set, Tuple)
> > @@ -268,9 +269,10 @@ class JsonEvent:
> >      self.metric_name = jd.get('MetricName')
> >      self.metric_group = jd.get('MetricGroup')
> >      self.metric_constraint = jd.get('MetricConstraint')
> > -    self.metric_expr = jd.get('MetricExpr')
> > -    if self.metric_expr:
> > -      self.metric_expr = self.metric_expr.replace('\\', '\\\\')
> > +    self.metric_expr = None
> > +    if 'MetricExpr' in jd:
> > +       self.metric_expr = metric.ParsePerfJson(jd['MetricExpr']).Simplify()
> > +
> >      arch_std = jd.get('ArchStdEvent')
> >      if precise and self.desc and '(Precise Event)' not in self.desc:
> >        extra_desc += ' (Must be precise)' if precise == '2' else (' (Precise '
> > @@ -322,6 +324,10 @@ class JsonEvent:
> >      s = ''
> >      for attr in _json_event_attributes:
> >        x = getattr(self, attr)
> > +      if x and attr == 'metric_expr':
> > +        # Convert parsed metric expressions into a string. Slashes
> > +        # must be doubled in the file.
> > +        x = x.ToPerfJson().replace('\\', '\\\\')
> >        s += f'{x}\\000' if x else '\\000'
> >      return s
> >
> > diff --git a/tools/perf/pmu-events/metric.py b/tools/perf/pmu-events/metric.py
> > new file mode 100644
> > index 000000000000..cc451a265751
> > --- /dev/null
> > +++ b/tools/perf/pmu-events/metric.py
> > @@ -0,0 +1,501 @@
> > +# SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
> > +"""Parse or generate representations of perf metrics."""
> > +import ast
> > +import decimal
> > +import json
> > +import re
> > +from typing import Dict, List, Optional, Set, Union
> > +
> > +
> > +class Expression:
> > +  """Abstract base class of elements in a metric expression."""
> > +
> > +  def ToPerfJson(self) -> str:
> > +    """Returns a perf json file encoded representation."""
> > +    raise NotImplementedError()
> > +
> > +  def ToPython(self) -> str:
> > +    """Returns a python expr parseable representation."""
> > +    raise NotImplementedError()
> > +
> > +  def Simplify(self):
> > +    """Returns a simplified version of self."""
> > +    raise NotImplementedError()
> > +
> > +  def Equals(self, other) -> bool:
> > +    """Returns true when two expressions are the same."""
> > +    raise NotImplementedError()
> > +
> > +  def __str__(self) -> str:
> > +    return self.ToPerfJson()
> > +
> > +  def __or__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('|', self, other)
> > +
> > +  def __ror__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('|', other, self)
> > +
> > +  def __xor__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('^', self, other)
> > +
> > +  def __and__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('&', self, other)
> > +
> > +  def __lt__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('<', self, other)
> > +
> > +  def __gt__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('>', self, other)
> > +
> > +  def __add__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('+', self, other)
> > +
> > +  def __radd__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('+', other, self)
> > +
> > +  def __sub__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('-', self, other)
> > +
> > +  def __rsub__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('-', other, self)
> > +
> > +  def __mul__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('*', self, other)
> > +
> > +  def __rmul__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('*', other, self)
> > +
> > +  def __truediv__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('/', self, other)
> > +
> > +  def __rtruediv__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('/', other, self)
> > +
> > +  def __mod__(self, other: Union[int, float, 'Expression']) -> 'Operator':
> > +    return Operator('%', self, other)
> > +
> > +
> > +def _Constify(val: Union[bool, int, float, Expression]) -> Expression:
> > +  """Used to ensure that the nodes in the expression tree are all Expression."""
> > +  if isinstance(val, bool):
> > +    return Constant(1 if val else 0)
> > +  if isinstance(val, (int, float)):
> > +    return Constant(val)
> > +  return val
> > +
> > +
> > +# Simple lookup for operator precedence, used to avoid unnecessary
> > +# brackets. Precedence matches that of python and the simple expression parser.
> > +_PRECEDENCE = {
> > +    '|': 0,
> > +    '^': 1,
> > +    '&': 2,
> > +    '<': 3,
> > +    '>': 3,
> > +    '+': 4,
> > +    '-': 4,
> > +    '*': 5,
> > +    '/': 5,
> > +    '%': 5,
> > +}
> > +
> > +
> > +class Operator(Expression):
> > +  """Represents a binary operator in the parse tree."""
> > +
> > +  def __init__(self, operator: str, lhs: Union[int, float, Expression],
> > +               rhs: Union[int, float, Expression]):
> > +    self.operator = operator
> > +    self.lhs = _Constify(lhs)
> > +    self.rhs = _Constify(rhs)
> > +
> > +  def Bracket(self,
> > +              other: Expression,
> > +              other_str: str,
> > +              rhs: bool = False) -> str:
> > +    """If necessary brackets the given other value.
> > +
> > +    If ``other`` is an operator then a bracket is necessary when
> > +    this/self operator has higher precedence. Consider: '(a + b) * c',
> > +    ``other_str`` will be 'a + b'. A bracket is necessary as without
> > +    the bracket 'a + b * c' will evaluate 'b * c' first. However, '(a
> > +    * b) + c' doesn't need a bracket as 'a * b' will always be
> > +    evaluated first. For 'a / (b * c)' (ie the same precedence level
> > +    operations) then we add the bracket to best match the original
> > +    input, but not for '(a / b) * c' where the bracket is unnecessary.
> > +
> > +    Args:
> > +      other (Expression): is a lhs or rhs operator
> > +      other_str (str): ``other`` in the appropriate string form
> > +      rhs (bool):  is ``other`` on the RHS
> > +
> > +    Returns:
> > +      str: possibly bracketed other_str
> > +    """
> > +    if isinstance(other, Operator):
> > +      if _PRECEDENCE.get(self.operator, -1) > _PRECEDENCE.get(
> > +          other.operator, -1):
> > +        return f'({other_str})'
> > +      if rhs and _PRECEDENCE.get(self.operator, -1) == _PRECEDENCE.get(
> > +          other.operator, -1):
> > +        return f'({other_str})'
> > +    return other_str
> > +
> > +  def ToPerfJson(self):
> > +    return (f'{self.Bracket(self.lhs, self.lhs.ToPerfJson())} {self.operator} '
> > +            f'{self.Bracket(self.rhs, self.rhs.ToPerfJson(), True)}')
> > +
> > +  def ToPython(self):
> > +    return (f'{self.Bracket(self.lhs, self.lhs.ToPython())} {self.operator} '
> > +            f'{self.Bracket(self.rhs, self.rhs.ToPython(), True)}')
> > +
> > +  def Simplify(self) -> Expression:
> > +    lhs = self.lhs.Simplify()
> > +    rhs = self.rhs.Simplify()
> > +    if isinstance(lhs, Constant) and isinstance(rhs, Constant):
> > +      return Constant(ast.literal_eval(lhs + self.operator + rhs))
> > +
> > +    if isinstance(self.lhs, Constant):
> > +      if self.operator in ('+', '|') and lhs.value == '0':
> > +        return rhs
> > +
> > +      # Simplify multiplication by 0 except for the slot event which
> > +      # is deliberately introduced using this pattern.
> > +      if self.operator == '*' and lhs.value == '0' and (
> > +          not isinstance(rhs, Event) or 'slots' not in rhs.name.lower()):
> > +        return Constant(0)
> > +
> > +      if self.operator == '*' and lhs.value == '1':
> > +        return rhs
> > +
> > +    if isinstance(rhs, Constant):
> > +      if self.operator in ('+', '|') and rhs.value == '0':
> > +        return lhs
> > +
> > +      if self.operator == '*' and rhs.value == '0':
> > +        return Constant(0)
> > +
> > +      if self.operator == '*' and self.rhs.value == '1':
> > +        return lhs
> > +
> > +    return Operator(self.operator, lhs, rhs)
> > +
> > +  def Equals(self, other: Expression) -> bool:
> > +    if isinstance(other, Operator):
> > +      return self.operator == other.operator and self.lhs.Equals(
> > +          other.lhs) and self.rhs.Equals(other.rhs)
> > +    return False
> > +
> > +
> > +class Select(Expression):
> > +  """Represents a select ternary in the parse tree."""
> > +
> > +  def __init__(self, true_val: Union[int, float, Expression],
> > +               cond: Union[int, float, Expression],
> > +               false_val: Union[int, float, Expression]):
> > +    self.true_val = _Constify(true_val)
> > +    self.cond = _Constify(cond)
> > +    self.false_val = _Constify(false_val)
> > +
> > +  def ToPerfJson(self):
> > +    true_str = self.true_val.ToPerfJson()
> > +    cond_str = self.cond.ToPerfJson()
> > +    false_str = self.false_val.ToPerfJson()
> > +    return f'({true_str} if {cond_str} else {false_str})'
> > +
> > +  def ToPython(self):
> > +    return (f'Select({self.true_val.ToPython()}, {self.cond.ToPython()}, '
> > +            f'{self.false_val.ToPython()})')
> > +
> > +  def Simplify(self) -> Expression:
> > +    cond = self.cond.Simplify()
> > +    true_val = self.true_val.Simplify()
> > +    false_val = self.false_val.Simplify()
> > +    if isinstance(cond, Constant):
> > +      return false_val if cond.value == '0' else true_val
> > +
> > +    if true_val.Equals(false_val):
> > +      return true_val
> > +
> > +    return Select(true_val, cond, false_val)
> > +
> > +  def Equals(self, other: Expression) -> bool:
> > +    if isinstance(other, Select):
> > +      return self.cond.Equals(other.cond) and self.false_val.Equals(
> > +          other.false_val) and self.true_val.Equals(other.true_val)
> > +    return False
> > +
> > +
> > +class Function(Expression):
> > +  """A function in an expression like min, max, d_ratio."""
> > +
> > +  def __init__(self,
> > +               fn: str,
> > +               lhs: Union[int, float, Expression],
> > +               rhs: Optional[Union[int, float, Expression]] = None):
> > +    self.fn = fn
> > +    self.lhs = _Constify(lhs)
> > +    self.rhs = _Constify(rhs)
> > +
> > +  def ToPerfJson(self):
> > +    if self.rhs:
> > +      return f'{self.fn}({self.lhs.ToPerfJson()}, {self.rhs.ToPerfJson()})'
> > +    return f'{self.fn}({self.lhs.ToPerfJson()})'
> > +
> > +  def ToPython(self):
> > +    if self.rhs:
> > +      return f'{self.fn}({self.lhs.ToPython()}, {self.rhs.ToPython()})'
> > +    return f'{self.fn}({self.lhs.ToPython()})'
> > +
> > +  def Simplify(self) -> Expression:
> > +    lhs = self.lhs.Simplify()
> > +    rhs = self.rhs.Simplify() if self.rhs else None
> > +    if isinstance(lhs, Constant) and isinstance(rhs, Constant):
> > +      if self.fn == 'd_ratio':
> > +        if rhs.value == '0':
> > +          return Constant(0)
> > +        Constant(ast.literal_eval(f'{lhs} / {rhs}'))
> > +      return Constant(ast.literal_eval(f'{self.fn}({lhs}, {rhs})'))
> > +
> > +    return Function(self.fn, lhs, rhs)
> > +
> > +  def Equals(self, other: Expression) -> bool:
> > +    if isinstance(other, Function):
> > +      return self.fn == other.fn and self.lhs.Equals(
> > +          other.lhs) and self.rhs.Equals(other.rhs)
> > +    return False
> > +
> > +
> > +def _FixEscapes(s: str) -> str:
> > +  s = re.sub(r'([^\\]),', r'\1\\,', s)
> > +  return re.sub(r'([^\\])=', r'\1\\=', s)
> > +
> > +
> > +class Event(Expression):
> > +  """An event in an expression."""
> > +
> > +  def __init__(self, name: str, legacy_name: str = ''):
> > +    self.name = _FixEscapes(name)
> > +    self.legacy_name = _FixEscapes(legacy_name)
> > +
> > +  def ToPerfJson(self):
> > +    result = re.sub('/', '@', self.name)
> > +    return result
> > +
> > +  def ToPython(self):
> > +    return f'Event(r"{self.name}")'
> > +
> > +  def Simplify(self) -> Expression:
> > +    return self
> > +
> > +  def Equals(self, other: Expression) -> bool:
> > +    return isinstance(other, Event) and self.name == other.name
> > +
> > +
> > +class Constant(Expression):
> > +  """A constant within the expression tree."""
> > +
> > +  def __init__(self, value: Union[float, str]):
> > +    ctx = decimal.Context()
> > +    ctx.prec = 20
> > +    dec = ctx.create_decimal(repr(value) if isinstance(value, float) else value)
> > +    self.value = dec.normalize().to_eng_string()
> > +    self.value = self.value.replace('+', '')
> > +    self.value = self.value.replace('E', 'e')
> > +
> > +  def ToPerfJson(self):
> > +    return self.value
> > +
> > +  def ToPython(self):
> > +    return f'Constant({self.value})'
> > +
> > +  def Simplify(self) -> Expression:
> > +    return self
> > +
> > +  def Equals(self, other: Expression) -> bool:
> > +    return isinstance(other, Constant) and self.value == other.value
> > +
> > +
> > +class Literal(Expression):
> > +  """A runtime literal within the expression tree."""
> > +
> > +  def __init__(self, value: str):
> > +    self.value = value
> > +
> > +  def ToPerfJson(self):
> > +    return self.value
> > +
> > +  def ToPython(self):
> > +    return f'Literal({self.value})'
> > +
> > +  def Simplify(self) -> Expression:
> > +    return self
> > +
> > +  def Equals(self, other: Expression) -> bool:
> > +    return isinstance(other, Literal) and self.value == other.value
> > +
> > +
> > +def min(lhs: Union[int, float, Expression], rhs: Union[int, float,
> > +                                                       Expression]) -> Function:
> > +  # pylint: disable=redefined-builtin
> > +  # pylint: disable=invalid-name
> > +  return Function('min', lhs, rhs)
> > +
> > +
> > +def max(lhs: Union[int, float, Expression], rhs: Union[int, float,
> > +                                                       Expression]) -> Function:
> > +  # pylint: disable=redefined-builtin
> > +  # pylint: disable=invalid-name
> > +  return Function('max', lhs, rhs)
> > +
> > +
> > +def d_ratio(lhs: Union[int, float, Expression],
> > +            rhs: Union[int, float, Expression]) -> Function:
> > +  # pylint: disable=redefined-builtin
> > +  # pylint: disable=invalid-name
> > +  return Function('d_ratio', lhs, rhs)
> > +
> > +
> > +def source_count(event: Event) -> Function:
> > +  # pylint: disable=redefined-builtin
> > +  # pylint: disable=invalid-name
> > +  return Function('source_count', event)
> > +
> > +
> > +class Metric:
> > +  """An individual metric that will specifiable on the perf command line."""
> > +  groups: Set[str]
> > +  expr: Expression
> > +  scale_unit: str
> > +  constraint: bool
> > +
> > +  def __init__(self,
> > +               name: str,
> > +               description: str,
> > +               expr: Expression,
> > +               scale_unit: str,
> > +               constraint: bool = False):
> > +    self.name = name
> > +    self.description = description
> > +    self.expr = expr.Simplify()
> > +    # Workraound valid_only_metric hiding certain metrics based on unit.
> > +    scale_unit = scale_unit.replace('/sec', ' per sec')
> > +    if scale_unit[0].isdigit():
> > +      self.scale_unit = scale_unit
> > +    else:
> > +      self.scale_unit = f'1{scale_unit}'
> > +    self.constraint = constraint
> > +    self.groups = set()
> > +
> > +  def __lt__(self, other):
> > +    """Sort order."""
> > +    return self.name < other.name
> > +
> > +  def AddToMetricGroup(self, group):
> > +    """Callback used when being added to a MetricGroup."""
> > +    self.groups.add(group.name)
> > +
> > +  def Flatten(self) -> Set['Metric']:
> > +    """Return a leaf metric."""
> > +    return set([self])
> > +
> > +  def ToPerfJson(self) -> Dict[str, str]:
> > +    """Return as dictionary for Json generation."""
> > +    result = {
> > +        'MetricName': self.name,
> > +        'MetricGroup': ';'.join(sorted(self.groups)),
> > +        'BriefDescription': self.description,
> > +        'MetricExpr': self.expr.ToPerfJson(),
> > +        'ScaleUnit': self.scale_unit
> > +    }
> > +    if self.constraint:
> > +      result['MetricConstraint'] = 'NO_NMI_WATCHDOG'
> > +
> > +    return result
> > +
> > +
> > +class _MetricJsonEncoder(json.JSONEncoder):
> > +  """Special handling for Metric objects."""
> > +
> > +  def default(self, o):
> > +    if isinstance(o, Metric):
> > +      return o.ToPerfJson()
> > +    return json.JSONEncoder.default(self, o)
> > +
> > +
> > +class MetricGroup:
> > +  """A group of metrics.
> > +
> > +  Metric groups may be specificd on the perf command line, but within
> > +  the json they aren't encoded. Metrics may be in multiple groups
> > +  which can facilitate arrangements similar to trees.
> > +  """
> > +
> > +  def __init__(self, name: str, metric_list: List[Union[Metric,
> > +                                                        'MetricGroup']]):
> > +    self.name = name
> > +    self.metric_list = metric_list
> > +    for metric in metric_list:
> > +      metric.AddToMetricGroup(self)
> > +
> > +  def AddToMetricGroup(self, group):
> > +    """Callback used when a MetricGroup is added into another."""
> > +    for metric in self.metric_list:
> > +      metric.AddToMetricGroup(group)
> > +
> > +  def Flatten(self) -> Set[Metric]:
> > +    """Returns a set of all leaf metrics."""
> > +    result = set()
> > +    for x in self.metric_list:
> > +      result = result.union(x.Flatten())
> > +
> > +    return result
> > +
> > +  def ToPerfJson(self) -> str:
> > +    return json.dumps(sorted(self.Flatten()), indent=2, cls=_MetricJsonEncoder)
> > +
> > +  def __str__(self) -> str:
> > +    return self.ToPerfJson()
> > +
> > +
> > +class _RewriteIfExpToSelect(ast.NodeTransformer):
> > +
> > +  def visit_IfExp(self, node):
> > +    # pylint: disable=invalid-name
> > +    call = ast.Call(
> > +        func=ast.Name(id='Select', ctx=ast.Load()),
> > +        args=[node.body, node.test, node.orelse],
> > +        keywords=[])
> > +    ast.copy_location(call, node.test)
> > +    return call
> > +
> > +
> > +def ParsePerfJson(orig: str) -> Expression:
> > +  """A simple json metric expression decoder.
> > +
> > +  Converts a json encoded metric expression by way of python's ast and
> > +  eval routine. First tokens are mapped to Event calls, then
> > +  accidentally converted keywords or literals are mapped to their
> > +  appropriate calls. Python's ast is used to match if-else that can't
> > +  be handled via operator overloading. Finally the ast is evaluated.
> > +
> > +  Args:
> > +    orig (str): String to parse.
> > +
> > +  Returns:
> > +    Expression: The parsed string.
> > +  """
> > +  # pylint: disable=eval-used
> > +  py = orig.strip()
> > +  py = re.sub(r'([a-zA-Z][^-+/\* \\\(\),]*(?:\\.[^-+/\* \\\(\),]*)*)',
> > +              r'Event(r"\1")', py)
> > +  py = re.sub(r'#Event\(r"([^"]*)"\)', r'Literal("#\1")', py)
> > +  py = re.sub(r'([0-9]+)Event\(r"(e[0-9]+)"\)', r'\1\2', py)
> > +  keywords = ['if', 'else', 'min', 'max', 'd_ratio', 'source_count']
> > +  for kw in keywords:
> > +    py = re.sub(rf'Event\(r"{kw}"\)', kw, py)
> > +
> > +  parsed = ast.parse(py, mode='eval')
> > +  _RewriteIfExpToSelect().visit(parsed)
> > +  parsed = ast.fix_missing_locations(parsed)
> > +  return _Constify(eval(compile(parsed, orig, 'eval')))
> > diff --git a/tools/perf/pmu-events/metric_test.py b/tools/perf/pmu-events/metric_test.py
> > new file mode 100644
> > index 000000000000..4741b7b6612d
> > --- /dev/null
> > +++ b/tools/perf/pmu-events/metric_test.py
> > @@ -0,0 +1,153 @@
> > +# SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
> > +import unittest
> > +from metric import Constant
> > +from metric import Event
> > +from metric import ParsePerfJson
> > +
> > +
> > +class TestMetricExpressions(unittest.TestCase):
> > +
> > +  def test_Operators(self):
> > +    a = Event('a')
> > +    b = Event('b')
> > +    self.assertEqual((a | b).ToPerfJson(), 'a | b')
> > +    self.assertEqual((a ^ b).ToPerfJson(), 'a ^ b')
> > +    self.assertEqual((a & b).ToPerfJson(), 'a & b')
> > +    self.assertEqual((a < b).ToPerfJson(), 'a < b')
> > +    self.assertEqual((a > b).ToPerfJson(), 'a > b')
> > +    self.assertEqual((a + b).ToPerfJson(), 'a + b')
> > +    self.assertEqual((a - b).ToPerfJson(), 'a - b')
> > +    self.assertEqual((a * b).ToPerfJson(), 'a * b')
> > +    self.assertEqual((a / b).ToPerfJson(), 'a / b')
> > +    self.assertEqual((a % b).ToPerfJson(), 'a % b')
> > +    one = Constant(1)
> > +    self.assertEqual((a + one).ToPerfJson(), 'a + 1')
> > +
> > +  def test_Brackets(self):
> > +    a = Event('a')
> > +    b = Event('b')
> > +    c = Event('c')
> > +    self.assertEqual((a * b + c).ToPerfJson(), 'a * b + c')
> > +    self.assertEqual((a + b * c).ToPerfJson(), 'a + b * c')
> > +    self.assertEqual(((a + a) + a).ToPerfJson(), 'a + a + a')
> > +    self.assertEqual(((a + b) * c).ToPerfJson(), '(a + b) * c')
> > +    self.assertEqual((a + (b * c)).ToPerfJson(), 'a + b * c')
> > +    self.assertEqual(((a / b) * c).ToPerfJson(), 'a / b * c')
> > +    self.assertEqual((a / (b * c)).ToPerfJson(), 'a / (b * c)')
> > +
> > +  def test_ParsePerfJson(self):
> > +    # Based on an example of a real metric.
> > +    before = '(a + b + c + d) / (2 * e)'
> > +    after = before
> > +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> > +
> > +    # Parsing should handle events with '-' in their name. Note, in
> > +    # the json file the '\' are doubled to '\\'.
> > +    before = r'topdown\-fe\-bound / topdown\-slots - 1'
> > +    after = before
> > +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> > +
> > +    # Parsing should handle escaped modifiers. Note, in the json file
> > +    # the '\' are doubled to '\\'.
> > +    before = r'arb@...nt\=0x81\,umask\=0x1@ + arb@...nt\=0x84\,umask\=0x1@'
> > +    after = before
> > +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> > +
> > +    # Parsing should handle exponents in numbers.
> > +    before = r'a + 1e12 + b'
> > +    after = before
> > +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> > +
> > +  def test_IfElseTests(self):
> > +    # if-else needs rewriting to Select and back.
> > +    before = r'Event1 if #smt_on else Event2'
> > +    after = f'({before})'
> > +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> > +
> > +    before = r'Event1 if 0 else Event2'
> > +    after = f'({before})'
> > +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> > +
> > +    before = r'Event1 if 1 else Event2'
> > +    after = f'({before})'
> > +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> > +
> > +    # Ensure the select is evaluate last.
> > +    before = r'Event1 + 1 if Event2 < 2 else Event3 + 3'
> > +    after = (r'Select(Event(r"Event1") + Constant(1), Event(r"Event2") < '
> > +             r'Constant(2), Event(r"Event3") + Constant(3))')
> > +    self.assertEqual(ParsePerfJson(before).ToPython(), after)
> > +
> > +    before = r'Event1 > 1 if Event2 < 2 else Event3 > 3'
> > +    after = (r'Select(Event(r"Event1") > Constant(1), Event(r"Event2") < '
> > +             r'Constant(2), Event(r"Event3") > Constant(3))')
> > +    self.assertEqual(ParsePerfJson(before).ToPython(), after)
> > +
> > +    before = r'min(a + b if c > 1 else c + d, e + f)'
> > +    after = r'min((a + b if c > 1 else c + d), e + f)'
> > +    self.assertEqual(ParsePerfJson(before).ToPerfJson(), after)
> > +
> > +  def test_ToPython(self):
> > +    # pylint: disable=eval-used
> > +    # Based on an example of a real metric.
> > +    before = '(a + b + c + d) / (2 * e)'
> > +    py = ParsePerfJson(before).ToPython()
> > +    after = eval(py).ToPerfJson()
> > +    self.assertEqual(before, after)
> > +
> > +  def test_Simplify(self):
> > +    before = '1 + 2 + 3'
> > +    after = '6'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +    before = 'a + 0'
> > +    after = 'a'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +    before = '0 + a'
> > +    after = 'a'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +    before = 'a | 0'
> > +    after = 'a'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +    before = '0 | a'
> > +    after = 'a'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +    before = 'a * 0'
> > +    after = '0'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +    before = '0 * a'
> > +    after = '0'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +    before = 'a * 1'
> > +    after = 'a'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +    before = '1 * a'
> > +    after = 'a'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +    before = 'a if 0 else b'
> > +    after = 'b'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +    before = 'a if 1 else b'
> > +    after = 'a'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +    before = 'a if b else a'
> > +    after = 'a'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +    # Pattern used to add a slots event to metrics that require it.
> > +    before = '0 * SLOTS'
> > +    after = '0 * SLOTS'
> > +    self.assertEqual(ParsePerfJson(before).Simplify().ToPerfJson(), after)
> > +
> > +if __name__ == '__main__':
> > +  unittest.main()
> > --
> > 2.39.0.rc0.267.gcb52ba06e7-goog
> >

-- 

- Arnaldo

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