profiler.py

import torch.autograd.profiler as prof
from torch.autograd import ProfilerActivity

from enum import Enum
from typing import Any, Callable, Iterable, Optional
from warnings import warn


class ProfilerAction(Enum):
    NONE = 0
    WARMUP = 1
    RECORD = 2
    RECORD_AND_SAVE = 3


def schedule(*, wait: int, warmup: int, active: int):
    """
    Represents profiler behavior: wait for ``wait`` steps, then
    do the warmup for the next ``warmup`` steps, then
    do the active recording for the next ``active`` steps and then
    repeat the cycle staring with the next step.
    """
    def schedule_fn(step: int) -> ProfilerAction:
        assert step >= 0
        num_steps = wait + warmup + active
        mod_step = step % num_steps
        if mod_step < wait:
            return ProfilerAction.NONE
        elif mod_step < wait + warmup:
            return ProfilerAction.WARMUP
        else:
            return ProfilerAction.RECORD if mod_step < num_steps - 1 \
                else ProfilerAction.RECORD_AND_SAVE
    assert wait >= 0 and warmup >= 0 and active > 0, \
        "Invalid profiler schedule arguments"
    if warmup == 0:
        warn("Profiler won't be using warmup, this can skew profiler results")
    return schedule_fn


def _default_schedule_fn(_: int) -> ProfilerAction:
    """
    Default profiler behavior - immediately starts recording the events,
    keeps doing it on every profiler step.
    """
    return ProfilerAction.RECORD


class profile(object):
    """
    Profiler context manager.

    Arguments:

    - ``activities`` - list of activity groups (CPU, CUDA) to use in profiling;
    - ``schedule`` - callable that takes step (int) as a single parameter and returns
      ``ProfilerAction`` value that specifies the profiler action on each step;
    - ``on_trace_ready`` (optional) - callable, called each time the trace is ready
      during the profiling;
    - ``record_shapes`` - save information about operator's input shapes;
    - ``profile_memory`` - track tensor memory allocation/deallocation;
    - ``with_stack`` - save stack traces;
    - ``use_gpu`` - (deprecated, use ``activities``).

    .. note::
        Use ``torch.profiler.schedule`` to generate the callable schedule.
        Non-default schedules are useful when profiling long training jobs
        and allow the user to obtain multiple traces at the different iterations
        of the training process.
        The default schedule simply records all the events continuously for the
        duration of the context manager.

    .. note::
        Enabling shape and stack tracing results in additional overhead.

    Examples:

    .. code-block:: python

        with torch.profiler.profile(
            activities=[
                torch.profiler.ProfilerActivity.CPU,
                torch.profiler.ProfilerActivity.CUDA]
        ) as p:
            code_to_profile()
        print(p.key_averages().table(
            sort_by="self_cuda_time_total", row_limit=-1))

    Usimg the profiler's ``schedule``, ``on_trace_ready`` and ``next_step`` functions:

    .. code-block:: python

        # Non-default profiler schedule allows user to turn profiler on and off
        # on different iterations of the training loop;
        # trace_handler is called every time a new trace becomes available
        def trace_handler(prof):
            print(prof.key_averages().table(
                sort_by="self_cuda_time_total", row_limit=-1))
            # prof.export_chrome_trace("/tmp/test_trace_" + str(prof.step()) + ".json")

        with torch.profiler.profile(
            activities=[
                torch.profiler.ProfilerActivity.CPU,
                torch.profiler.ProfilerActivity.CUDA],

            # In this example with wait=1, warmup=1, active=2,
            # profiler will skip the first step/iteration,
            # start warming up on the second, record
            # the third and the forth iterations,
            # after which the trace will become available
            # and on_trace_ready (when set) is called;
            # the cycle repeats starting with the next step

            schedule=torch.profiler.schedule(
                wait=1,
                warmup=1,
                active=2),
            on_trace_ready=trace_handler
            ) as p:
                for iter in range(N):
                    code_iteration_to_profile(iter)
                    # send a signal to the profiler that the next iteration has started
                    p.next_step()
    """
    def __init__(
            self,
            *,
            activities: Optional[Iterable[ProfilerActivity]] = None,
            schedule: Optional[Callable[[int], ProfilerAction]] = None,
            on_trace_ready: Optional[Callable[..., Any]] = None,
            record_shapes: bool = False,
            profile_memory: bool = False,
            with_stack: bool = False,
            # deprecated:
            use_gpu: Optional[bool] = None):
        if activities:
            self.activities = activities
        else:
            if use_gpu is not None:
                warn("use_gpu is deprecated, use activities argument instead")
                self.activities = set([ProfilerActivity.CPU])
                if use_gpu:
                    self.activities.add(ProfilerActivity.CUDA)
            else:
                raise RuntimeError("Profiler activities are not specified")

        if schedule:
            self.schedule = schedule
            # add step markers into the trace and table view
            self.record_steps = True
        else:
            self.schedule = _default_schedule_fn
            self.record_steps = False
        self.on_trace_ready = on_trace_ready
        self.record_shapes = record_shapes
        self.profile_memory = profile_memory
        self.with_stack = with_stack
        self.step_num = 0
        self.current_action = self.schedule(self.step_num)
        self.profiler: Optional[prof.profile] = None
        self.step_rec_fn: Optional[prof.record_function] = None

    def __enter__(self):
        self._enter_actions()
        if self.record_steps:
            self.step_rec_fn = prof.record_function("ProfilerStep#" + str(self.step_num))
            self.step_rec_fn.__enter__()
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        if self.record_steps and self.step_rec_fn:
            self.step_rec_fn.__exit__(None, None, None)
        self._exit_actions()

    def next_step(self):
        """
        Signals the profiler that the next profiling step has started.
        """
        if self.record_steps and self.step_rec_fn:
            self.step_rec_fn.__exit__(None, None, None)
        prev_action = self.current_action
        self.step_num += 1
        self.current_action = self.schedule(self.step_num)

        if self.current_action == ProfilerAction.NONE:
            if prev_action == ProfilerAction.NONE:
                pass
            elif prev_action == ProfilerAction.WARMUP:
                warn("Incorrect schedule: WARMUP followed by NONE")
                self._start_trace()
                self._stop_trace()
            elif prev_action == ProfilerAction.RECORD:
                warn("Incorrect schedule: RECORD followed by NONE")
                self._stop_trace()
            else:
                assert prev_action == ProfilerAction.RECORD_AND_SAVE
                self._stop_trace()
                if self.on_trace_ready:
                    self.on_trace_ready(self)
        elif self.current_action == ProfilerAction.WARMUP:
            if prev_action == ProfilerAction.NONE:
                self._start_warmup()
            elif prev_action == ProfilerAction.WARMUP:
                pass
            elif prev_action == ProfilerAction.RECORD:
                warn("Incorrect schedule: RECORD followed by WARMUP")
                self._stop_trace()
            else:
                assert prev_action == ProfilerAction.RECORD_AND_SAVE
                self._stop_trace()
                if self.on_trace_ready:
                    self.on_trace_ready(self)
                self._start_warmup()
        elif self.current_action in \
                [ProfilerAction.RECORD, ProfilerAction.RECORD_AND_SAVE]:
            if prev_action == ProfilerAction.NONE:
                self._start_warmup()
                self._start_trace()
            elif prev_action == ProfilerAction.WARMUP:
                self._start_trace()
            elif prev_action == ProfilerAction.RECORD:
                pass
            else:
                assert prev_action == ProfilerAction.RECORD_AND_SAVE
                self._stop_trace()
                if self.on_trace_ready:
                    self.on_trace_ready(self)
                self._start_warmup()
                self._start_trace()

        if self.record_steps:
            self.step_rec_fn = prof.record_function("ProfilerStep#" + str(self.step_num))
            self.step_rec_fn.__enter__()

    def step(self):
        """
        Returns the current profiling step.
        """
        return self.step_num

    def export_chrome_trace(self, path: str):
        """
        Exports the collected trace in Chrome JSON format.
        """
        assert self.profiler
        return self.profiler.export_chrome_trace(path)

    def export_stacks(self, path: str, metric: str = "self_cpu_time_total"):
        """
        Save stack traces in a file in a format suitable for visualization.

        Arguments:

        - ``path`` - save stacks file to this location;
        - ``metric`` - metric to use: "self_cpu_time_total" or "self_cuda_time_total"

        .. note::
            Example of using FlameGraph tool:

            - git clone https://github.com/brendangregg/FlameGraph
            - cd FlameGraph
            - ./flamegraph.pl --title "CPU time" --countname "us." profiler.stacks > perf_viz.svg
        """
        assert self.profiler
        return self.profiler.export_stacks(path, metric)

    def key_averages(self, group_by_input_shape: bool = False, group_by_stack_n: int = 0):
        """
        Averages events, grouping them by operator name and (optionally) input shapes and
        stack.
        Note: to use shape/stack functionality make sure to set record_shapes/with_stack
        when creating profiler context manager.
        """
        assert self.profiler
        return self.profiler.key_averages(group_by_input_shape, group_by_stack_n)

    def _enter_actions(self):
        if self.current_action == ProfilerAction.WARMUP:
            self._start_warmup()
        elif self.current_action in \
                [ProfilerAction.RECORD, ProfilerAction.RECORD_AND_SAVE]:
            self._start_warmup()
            self._start_trace()

    def _exit_actions(self):
        if self.current_action == ProfilerAction.WARMUP:
            self._start_trace()
            self._stop_trace()
        elif self.current_action in \
                [ProfilerAction.RECORD, ProfilerAction.RECORD_AND_SAVE]:
            self._stop_trace()
            if self.on_trace_ready:
                self.on_trace_ready(self)

    def _start_warmup(self):
        self.profiler = prof.profile(
            use_cuda=(ProfilerActivity.CUDA in self.activities),
            use_cpu=(ProfilerActivity.CPU in self.activities),
            record_shapes=self.record_shapes,
            profile_memory=self.profile_memory,
            with_stack=self.with_stack,
            use_kineto=True,
        )
        self.profiler._prepare_kineto_trace()

    def _start_trace(self):
        assert self.profiler is not None
        self.profiler._start_kineto_trace()

    def _stop_trace(self):
        assert self.profiler is not None
        self.profiler.__exit__(None, None, None)