# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project

"""
Analytic flops/memory estimation module for transformer components,
to help derive MFU (Model Flops Utilization) stats for a running model.
"""

import json
import time
from abc import ABC, abstractmethod
from collections.abc import Iterable
from dataclasses import asdict, dataclass
from typing import Any, Protocol

import torch
from pydantic import BaseModel, Field, ValidationError, model_validator
from typing_extensions import Self

import vllm.envs as envs
from vllm.config import VllmConfig
from vllm.logger import init_logger
from vllm.utils.torch_utils import (
    STR_DTYPE_TO_TORCH_DTYPE,
    get_dtype_size,
    get_kv_cache_torch_dtype,
)
from vllm.v1.core.sched.output import SchedulerOutput

logger = init_logger(__name__)


class InvalidComponent(Exception):
    """
    Custom exception to indicate that a certain ComponentMetric is not
    applicable to the given VllmConfig.
    """

    pass


#### Basic Data Types ####


@dataclass
class DebugPerfStats:
    ## Stats for debugging the metrics calculation
    calc_duration: float = 0.0  # time spent calculating these stats
    num_prefill_requests: int = 0
    num_decode_requests: int = 0
    context_breakdown: dict[str, int] | None = None
    num_flops_per_gpu_breakdown: dict[str, int] | None = None
    num_read_bytes_per_gpu_breakdown: dict[str, int] | None = None
    num_write_bytes_per_gpu_breakdown: dict[str, int] | None = None


@dataclass
class PerfStats:
    num_flops_per_gpu: int = 0
    num_read_bytes_per_gpu: int = 0
    num_write_bytes_per_gpu: int = 0
    debug_stats: DebugPerfStats | None = None


@dataclass
class ExecutionContext:
    """
    Represents an execution context for a batch of requests.

    This class aggregates statistics across multiple requests in a batch,
    separately tracking prefill and decode phases.

    Example)
    - Batch with one full prefill (2048 tokens) and one decode (1 token, 8192 context):
      ctx = ExecutionContext()
      ctx.add(2048, 2048, is_prefill=True)
      ctx.add(1, 8192, is_prefill=False)
    """

    # Prefill phase statistics
    num_prefill_requests: int = 0
    prefill_num_tokens: int = 0  # sum of num_tokens for prefill requests
    prefill_context_len: int = 0  # sum of context_len for prefill requests
    prefill_token_context_product: int = 0  # sum of (num_tokens * context_len)

    # Decode phase statistics
    num_decode_requests: int = 0
    decode_num_tokens: int = 0  # sum of num_tokens for decode requests
    decode_context_len: int = 0  # sum of context_len for decode requests
    decode_token_context_product: int = 0  # sum of (num_tokens * context_len)

    def add(self, num_tokens: int, context_len: int, is_prefill: bool) -> None:
        """Add a single request's statistics to this batch context."""
        if is_prefill:
            self.num_prefill_requests += 1
            self.prefill_num_tokens += num_tokens
            self.prefill_context_len += context_len
            self.prefill_token_context_product += num_tokens * context_len
        else:
            self.num_decode_requests += 1
            self.decode_num_tokens += num_tokens
            self.decode_context_len += context_len
            self.decode_token_context_product += num_tokens * context_len

    def total_num_tokens(self) -> int:
        """Total number of tokens across all requests in the batch."""
        return self.prefill_num_tokens + self.decode_num_tokens

    def total_token_context_product(self) -> int:
        """Total sum of (num_tokens * context_len) across all requests."""
        return self.prefill_token_context_product + self.decode_token_context_product

    def num_logits_tokens(self) -> int:
        """Number of tokens that require logits computation (unembedding).

        For prefill, only the last token per request needs logits.
        For decode, all tokens need logits.
        """
        return self.num_prefill_requests + self.decode_num_tokens

    @classmethod
    def from_single_request(
        cls, num_tokens: int, context_len: int, is_prefill: bool
    ) -> "ExecutionContext":
        """Create an ExecutionContext from a single request.

        This is a convenience method primarily for testing.
        """
        ctx = cls()
        ctx.add(num_tokens, context_len, is_prefill)
        return ctx


class ParsedArgs:
    """
    Syntactic sugar so that Parsers can use dot notations
    to access/update the parsed arguments.

    e.g.)
        args = ParsedArgs()
        args.x = 3
        args.y = args.x + 1
    """

    def __getattr__(self, name: str) -> Any:
        raise AttributeError(f"'{type(self).__name__}' has no attribute '{name}'")

    def __setattr__(self, name: str, value: Any) -> None:
        object.__setattr__(self, name, value)

    def model_dump(self) -> dict[str, Any]:
        return vars(self).copy()


#### Abstract ####


class Parser(Protocol):
    def parse(self, args: ParsedArgs, vllm_config: VllmConfig) -> ParsedArgs:
        """
        Parse the vllm config and update the current ParsedArgs and pass it on.
        If the parser isn't applicable to the vllm_config, it will do nothing.
        """
        ...


class ParserChain:
    """
    Applies chain of parser in a sequential order.
    Later parsers might overwrite results from previous parsers,
    so parsers should be chained in the appropriate order if they
    are not mutually exclusive.
    """

    def __init__(self, *parsers: Parser) -> None:
        self.parsers = list(parsers)

    def add_parser(self, parser: Parser) -> None:
        self.parsers.append(parser)

    def parse(self, vllm_config: VllmConfig) -> ParsedArgs:
        args = ParsedArgs()
        for parser in self.parsers:
            args = parser.parse(args, vllm_config)
        return args


_COMPONENT_METRICS_REGISTRY: dict[str, type["ComponentMetrics"]] = {}


class ComponentMetrics(BaseModel, ABC):
    """
    Each concrete ComponentMetrics class is associated with:
    - fields that are required for metric derivation
      (fields are specified/validated through pydantic model)
    - parser to parse VllmConfig into fields
    - metric methods that derive flops/bytes for a given execution context
    """

    @classmethod
    @abstractmethod
    def component_type(cls) -> str: ...

    @classmethod
    @abstractmethod
    def get_parser(cls) -> ParserChain:
        """
        Return a ParserChain that provides values for all required fields.
        The returned parser chain must populate ParsedArgs with values for every
        field defined on this ComponentMetrics class. Missing fields will cause
        a ValidationError when from_vllm_config() is called.
        See individual Parser docstrings for which args they provide, and field
        comments on ComponentMetrics subclasses for which parser provides each field.
        """
        ...

    def __init_subclass__(cls):
        _COMPONENT_METRICS_REGISTRY[cls.component_type()] = cls

    @classmethod
    def from_vllm_config(cls, vllm_config: VllmConfig) -> Self:
        """
        Instantiate this class from VllmConfig.
        Raises ValidationError if parsing fails.
        """

        parser = cls.get_parser()
        parsed_args = parser.parse(vllm_config)
        try:
            return cls.model_validate(parsed_args.model_dump())
        except ValidationError as e:
            raise InvalidComponent(f"Invalid {cls.component_type()} config: {e}") from e

    @classmethod
    def registered_metrics(cls) -> Iterable[type["ComponentMetrics"]]:
        return iter(_COMPONENT_METRICS_REGISTRY.values())

    @abstractmethod
    def get_num_flops_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]: ...

    @abstractmethod
    def get_read_bytes_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]: ...

    @abstractmethod
    def get_write_bytes_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]: ...

    def get_num_flops(self, ctx: ExecutionContext, per_gpu: bool = True) -> int:
        return sum(self.get_num_flops_breakdown(ctx, per_gpu).values())

    def get_read_bytes(self, ctx: ExecutionContext, per_gpu: bool = True) -> int:
        return sum(self.get_read_bytes_breakdown(ctx, per_gpu).values())

    def get_write_bytes(self, ctx: ExecutionContext, per_gpu: bool = True) -> int:
        return sum(self.get_write_bytes_breakdown(ctx, per_gpu).values())


#### parsers ####


class BaseConfigParser(Parser):
    """
    Parses base model configuration.
    Provides: vocab_size, hidden_size, num_attention_heads, num_hidden_layers,
    weight_byte_size, activation_byte_size, dp_size, tp_size, pp_size, enable_ep
    """

    def parse(self, args: ParsedArgs, vllm_config: VllmConfig) -> ParsedArgs:
        model_config = vllm_config.model_config

        args.vocab_size = model_config.get_vocab_size()
        args.hidden_size = model_config.get_hidden_size()
        # NOTE: model_config.get_attention_heads() divide by TP
        # so we access field manually here to get total num_heads
        args.num_attention_heads = get_required(
            model_config.hf_text_config, "num_attention_heads"
        )
        args.num_hidden_layers = get_required(
            model_config.hf_text_config, "num_hidden_layers"
        )

        model_dtype = vllm_config.model_config.dtype

        if isinstance(model_dtype, torch.dtype):
            torch_dtype = model_dtype
        elif isinstance(model_dtype, str) and model_dtype in STR_DTYPE_TO_TORCH_DTYPE:
            torch_dtype = STR_DTYPE_TO_TORCH_DTYPE[model_dtype]
        else:
            # FIXME: handle this better
            logger.warning(
                "Unknown model_dtype %s, defaulting to bfloat16",
                model_dtype,
            )
            torch_dtype = torch.bfloat16

        args.weight_byte_size = get_dtype_size(torch_dtype)

        # FIXME: handle this better by parsing whether activations use
        # bf16, fp32, etc...
        args.activation_byte_size = 2

        args.dp_size = vllm_config.parallel_config.data_parallel_size
        args.tp_size = vllm_config.parallel_config.tensor_parallel_size
        args.pp_size = vllm_config.parallel_config.pipeline_parallel_size
        args.enable_ep = vllm_config.parallel_config.enable_expert_parallel

        return args


#### Attention ####


class BaseAttentionConfigParser(Parser):
    """
    Parses attention-specific configuration.
    Provides: num_key_value_heads, head_dim, cache_byte_size
    """

    def parse(self, args: ParsedArgs, vllm_config: VllmConfig) -> ParsedArgs:
        model_config = vllm_config.model_config

        args.num_key_value_heads = model_config.get_total_num_kv_heads()
        args.head_dim = model_config.get_head_size()

        model_dtype = vllm_config.model_config.dtype
        cache_dtype = vllm_config.cache_config.cache_dtype

        kv_cache_torch_dtype = get_kv_cache_torch_dtype(cache_dtype, model_dtype)
        args.cache_byte_size = get_dtype_size(kv_cache_torch_dtype)

        return args


class AttentionQuantizationConfigParser(Parser):
    """
    Parses quantization configuration for attention layers.
    Overrides: weight_byte_size
    """

    def parse(self, args: ParsedArgs, vllm_config: VllmConfig) -> ParsedArgs:
        cfg = vllm_config.quant_config

        if cfg is None:
            return args

        quant_method = cfg.get_name()
        if quant_method in ["fp8", "fbgemm_fp8"]:
            # FIXME: This is a hacky coarse-grained fp8 quantization detection.
            # FIXME: These configs also have concept of "ignored layers" and we
            # need to solve the same problem as above.
            args.weight_byte_size = 1
        elif quant_method == "mxfp4":
            # FIXME: Also has "ignored layers" issue above
            args.weight_byte_size = 0.5
        else:
            # FIXME: Add more parsing logic for different quant methods.
            raise InvalidComponent

        return args


class AttentionMetrics(ComponentMetrics):
    # From BaseConfigParser
    num_hidden_layers: int = Field(..., gt=0)
    hidden_size: int = Field(..., gt=0)
    num_attention_heads: int = Field(..., gt=0)
    activation_byte_size: int = Field(..., gt=0)
    tp_size: int = Field(..., gt=0)
    pp_size: int = Field(..., gt=0)

    # From BaseAttentionConfigParser
    num_key_value_heads: int = Field(..., gt=0)
    head_dim: int = Field(..., gt=0)
    cache_byte_size: int = Field(..., gt=0)

    # From BaseConfig Parser, overridden by AttentionQuantizationConfigParser
    weight_byte_size: int | float = Field(..., gt=0)

    # TODO: discern cases where we have mixture of different attention layer types
    # such as SWA, MLA, etc.

    @classmethod
    def component_type(cls) -> str:
        return "attn"

    @classmethod
    def get_parser(cls) -> ParserChain:
        return ParserChain(
            BaseConfigParser(),
            BaseAttentionConfigParser(),
            AttentionQuantizationConfigParser(),
        )

    def get_num_flops_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]:
        L, D, q, kv, d = (
            self.num_hidden_layers,
            self.hidden_size,
            self.num_attention_heads,
            self.num_key_value_heads,
            self.head_dim,
        )
        T = ctx.total_num_tokens()
        TC = ctx.total_token_context_product()

        if per_gpu:
            L //= self.pp_size
            # tensor parallel along heads
            q = max(1, q // self.tp_size)
            kv = max(1, kv // self.tp_size)

        return {
            "qkv_proj": 2 * T * D * (q + 2 * kv) * d * L,
            "attn_qk": 2 * q * TC * d * L,
            "attn_av": 2 * q * TC * d * L,
            "out_proj": 2 * T * D * q * d * L,
        }

    def get_read_bytes_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]:
        L, D, q, kv, d = (
            self.num_hidden_layers,
            self.hidden_size,
            self.num_attention_heads,
            self.num_key_value_heads,
            self.head_dim,
        )
        T = ctx.total_num_tokens()

        if per_gpu:
            L //= self.pp_size
            # tensor parallel along heads
            q = max(1, q // self.tp_size)
            kv = max(1, kv // self.tp_size)

        read_bytes = {}

        read_bytes["qkv_input"] = T * D * self.activation_byte_size * L
        read_bytes["qkv_weight"] = int(D * (q + 2 * kv) * d * self.weight_byte_size * L)

        # Attention input reads differ between prefill and decode
        # Prefill: read Q, K, V activations (all in activation_byte_size)
        if ctx.prefill_num_tokens > 0:
            read_bytes["attn_input"] = (
                (ctx.prefill_num_tokens * q + 2 * ctx.prefill_context_len * kv)
                * d
                * self.activation_byte_size
                * L
            )

        # Decode: read Q activations + read K, V from cache (in cache_byte_size)
        if ctx.decode_num_tokens > 0:
            read_bytes["attn_input"] = read_bytes.get("attn_input", 0) + (
                ctx.decode_num_tokens * q * d * self.activation_byte_size * L
                + 2 * ctx.decode_context_len * kv * d * self.cache_byte_size * L
            )

        read_bytes["out_input"] = T * q * d * self.activation_byte_size * L
        read_bytes["out_weight"] = int(q * d * D * self.weight_byte_size * L)

        return read_bytes

    def get_write_bytes_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]:
        """Calculate write memory traffic for attention layers."""
        L, D, q, kv, d = (
            self.num_hidden_layers,
            self.hidden_size,
            self.num_attention_heads,
            self.num_key_value_heads,
            self.head_dim,
        )
        T = ctx.total_num_tokens()

        if per_gpu:
            L //= self.pp_size
            # tensor parallel along heads
            q = max(1, q // self.tp_size)
            kv = max(1, kv // self.tp_size)

        return {
            "qkv_output": T * (q + 2 * kv) * d * self.activation_byte_size * L,
            "kv_cache": 2 * T * kv * d * self.cache_byte_size * L,
            "out_output": T * D * self.activation_byte_size * L,
        }


#### Ffn ####


class BaseFfnConfigParser(Parser):
    """
    Parses FFN and MoE configuration.
    Provides: intermediate_size, num_experts, num_experts_per_tok,
    moe_intermediate_size, num_shared_experts, num_moe_layers
    """

    def parse(self, args: ParsedArgs, vllm_config: VllmConfig) -> ParsedArgs:
        cfg = vllm_config.model_config.hf_config
        if hasattr(cfg, "text_config") and cfg.text_config is not None:
            cfg = cfg.text_config

        args.intermediate_size = getattr(cfg, "intermediate_size", args.hidden_size * 4)

        # Try different naming conventions.
        args.num_experts = vllm_config.model_config.get_num_experts()
        args.num_experts_per_tok = getattr_from_list(
            cfg, ["num_experts_per_tok", "moe_topk"], 0
        )
        args.moe_intermediate_size = getattr_from_list(
            cfg, ["moe_intermediate_size", "intermediate_size"], 0
        )
        args.num_shared_experts = getattr_from_list(
            cfg, ["n_shared_experts", "num_shared_experts"], 0
        )

        is_moe = args.num_experts != 0
        # Assume all MoE layers by default
        args.num_moe_layers = args.num_hidden_layers if is_moe else 0

        return args


class FfnParallelParser(Parser):
    """
    Parses FFN parallelism configuration.

    Provides: ffn_tp_size, ffn_ep_size
    """

    def parse(self, args: ParsedArgs, vllm_config: VllmConfig) -> ParsedArgs:
        # NOTE: ffn tp_size does not equal the tp_size parameter directly.
        # e.g.) If we use DP2TP4, ffn will use TP8 (or EP8 if EP is enabled.)
        if args.enable_ep:
            ffn_tp_size, ffn_ep_size = 1, args.dp_size * args.tp_size
        else:
            ffn_tp_size, ffn_ep_size = args.dp_size * args.tp_size, 1

        args.ffn_tp_size = ffn_tp_size
        args.ffn_ep_size = ffn_ep_size

        return args


class InterleaveMoeLayerStepParser(Parser):
    """
    Parses interleave_moe_layer_step field for models like Llama4.

    Overrides: num_moe_layers
    """

    def parse(self, args: ParsedArgs, vllm_config: VllmConfig) -> ParsedArgs:
        cfg = vllm_config.model_config.hf_config
        if hasattr(cfg, "text_config") and cfg.text_config is not None:
            cfg = cfg.text_config

        if (
            hasattr(cfg, "interleave_moe_layer_step")
            and cfg.interleave_moe_layer_step > 0
        ):
            args.num_moe_layers = len(
                [
                    layer
                    for layer in range(args.num_hidden_layers)
                    if (layer + 1) % cfg.interleave_moe_layer_step == 0
                ]
            )

        return args


class MoeLayerFreqParser(Parser):
    """
    Parses moe_layer_freq and first_k_dense_replace fields for models like Deepseek.

    Overrides: num_moe_layers
    """

    def parse(self, args: ParsedArgs, vllm_config: VllmConfig) -> ParsedArgs:
        cfg = vllm_config.model_config.hf_config
        if hasattr(cfg, "text_config") and cfg.text_config is not None:
            cfg = cfg.text_config

        if hasattr(cfg, "moe_layer_freq") and hasattr(cfg, "first_k_dense_replace"):
            args.num_moe_layers = len(
                [
                    layer
                    for layer in range(args.num_hidden_layers)
                    if layer >= cfg.first_k_dense_replace
                    and layer % cfg.moe_layer_freq == 0
                ]
            )

        return args


class FfnQuantizationConfigParser(Parser):
    """
    Parses quantization configuration for FFN layers.

    Overrides: weight_byte_size
    """

    def parse(self, args: ParsedArgs, vllm_config: VllmConfig) -> ParsedArgs:
        cfg = vllm_config.quant_config

        if cfg is None:
            return args

        quant_method = cfg.get_name()
        if quant_method in ["fp8", "fbgemm_fp8"]:
            # FIXME: This is a hacky coarse-grained fp8 quantization detection.
            # (there might be more quantization methods for fp8).
            # FIXME: These configs also have concept of "ignored layers" and we
            # need to solve the same problem as above.
            args.weight_byte_size = 1
            pass
        elif quant_method == "mxfp4":
            # FIXME: Also has "ignored layers" issue above
            args.weight_byte_size = 0.5
        else:
            # FIXME: Add more parsing logic for different quant methods.
            raise InvalidComponent

        return args


class FfnMetrics(ComponentMetrics):
    # From BaseConfigParser
    num_hidden_layers: int = Field(..., gt=0)
    hidden_size: int = Field(..., gt=0)
    activation_byte_size: int = Field(..., gt=0)
    pp_size: int = Field(..., gt=0)

    # From FfnParallelParser
    ffn_tp_size: int = Field(..., gt=0)
    ffn_ep_size: int = Field(..., gt=0)

    # From BaseFfnConfigParser
    intermediate_size: int = Field(..., gt=0)
    num_experts: int = Field(0)
    num_experts_per_tok: int = Field(1)
    moe_intermediate_size: int = Field(0)
    num_shared_experts: int = Field(0)

    # From BaseConfigParser, can be overridden InterleaveMoeLayerStep or MoeLayerFreq
    num_moe_layers: int = Field(..., ge=0)

    # FIXME: might have to make this more granular
    # (i.e. dense_weight_byte_size, moe_routed_weight_byte_size,
    # moe_shared_weight_byte_size)
    # since it can differ from byte size of other components (e.g. attn)
    # and can differ even from each other.

    # From BaseConfigParser, can be overridden by FfnQuantizationConfigParser
    weight_byte_size: int | float = Field(..., gt=0)

    @model_validator(mode="after")
    def validate_moe_fields(self) -> Self:
        """Validate that MoE-related fields are properly set when num_moe_layers > 0."""
        if self.num_moe_layers > 0:
            assert self.num_experts, f"{self.num_experts=}"
            assert self.num_experts_per_tok, f"{self.num_experts_per_tok=}"
            assert self.moe_intermediate_size, f"{self.moe_intermediate_size=}"
        return self

    @classmethod
    def component_type(cls) -> str:
        return "ffn"

    @classmethod
    def get_parser(cls) -> ParserChain:
        return ParserChain(
            BaseConfigParser(),
            FfnParallelParser(),
            BaseFfnConfigParser(),
            InterleaveMoeLayerStepParser(),
            MoeLayerFreqParser(),
            FfnQuantizationConfigParser(),
        )

    def get_num_flops_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]:
        """Calculate flops breakdown for FFN layers."""
        L, D, DI = self.num_hidden_layers, self.hidden_size, self.intermediate_size
        Lm, E, MI, S = (
            self.num_moe_layers,
            self.num_experts_per_tok,
            self.moe_intermediate_size,
            self.num_shared_experts,
        )
        T = ctx.total_num_tokens()

        Ld = L - Lm

        num_activated_tokens = T * E if E else 0

        if per_gpu:
            Ld //= self.pp_size
            Lm //= self.pp_size

            DI //= self.ffn_tp_size
            if MI is not None:
                MI //= self.ffn_tp_size
            if E:
                num_activated_tokens //= self.ffn_ep_size

        flops = {}

        # Dense FFN layers (SwiGLU: 3 linear layers: up, gate, down)
        if Ld:
            flops["dense_ffn"] = 2 * D * 3 * DI * T * Ld

        # MoE routed experts (each token activates E experts)
        if Lm and E:
            flops["routed_ffn"] = 2 * D * 3 * MI * num_activated_tokens * Lm

        # MoE shared experts (all S shared experts run for every token)
        if Lm and S:
            flops["shared_ffn"] = 2 * D * 3 * MI * S * T * Lm

        return flops

    def get_read_bytes_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]:
        """Calculate read memory traffic for FFN layers."""
        L, D, DI = self.num_hidden_layers, self.hidden_size, self.intermediate_size
        Lm, E, MI, S = (
            self.num_moe_layers,
            self.num_experts_per_tok,
            self.moe_intermediate_size,
            self.num_shared_experts,
        )
        T = ctx.total_num_tokens()
        num_experts = self.num_experts

        Ld = L - Lm

        num_activated_tokens = T * E if E else 0

        if per_gpu:
            Ld //= self.pp_size
            Lm //= self.pp_size

            DI //= self.ffn_tp_size
            if MI is not None:
                MI //= self.ffn_tp_size
            if E:
                num_activated_tokens //= self.ffn_ep_size
            if num_experts is not None:
                num_experts //= self.ffn_ep_size

        read_bytes = {}

        # Dense FFN layers (3 GEMMs: up, gate, down projections + SiLU activation)
        if Ld:
            read_bytes["dense_up_gate_input"] = int(
                T * D * self.activation_byte_size * Ld
            )
            read_bytes["dense_up_gate_weights"] = int(
                2 * D * DI * self.weight_byte_size * Ld
            )
            read_bytes["dense_silu_input"] = int(
                2 * T * DI * self.activation_byte_size * Ld
            )
            read_bytes["dense_down_input"] = int(
                T * DI * self.activation_byte_size * Ld
            )
            read_bytes["dense_down_weights"] = int(D * DI * self.weight_byte_size * Ld)

        if Lm:
            # MoE routed expert reads
            if E:
                # FIXME: Assume perfect load balancing for now.
                num_activated_experts = min(num_activated_tokens, num_experts)

                read_bytes["routed_up_gate_input"] = int(
                    num_activated_tokens * D * self.activation_byte_size * Lm
                )
                read_bytes["routed_up_gate_weights"] = int(
                    2 * D * MI * num_activated_experts * self.weight_byte_size * Lm
                )
                read_bytes["routed_silu_input"] = int(
                    2 * num_activated_tokens * MI * self.activation_byte_size * Lm
                )
                read_bytes["routed_down_input"] = int(
                    num_activated_tokens * MI * self.activation_byte_size * Lm
                )
                read_bytes["routed_down_weights"] = int(
                    D * MI * num_activated_experts * self.weight_byte_size * Lm
                )

            # MoE shared expert reads
            if S:
                read_bytes["shared_up_gate_input"] = int(
                    T * D * self.activation_byte_size * Lm
                )
                read_bytes["shared_up_gate_weights"] = int(
                    2 * D * MI * S * self.weight_byte_size * Lm
                )
                read_bytes["shared_silu_input"] = int(
                    2 * T * MI * S * self.activation_byte_size * Lm
                )
                read_bytes["shared_down_input"] = int(
                    T * MI * self.activation_byte_size * Lm
                )
                read_bytes["shared_down_weights"] = int(
                    D * MI * S * self.weight_byte_size * Lm
                )

        return read_bytes

    def get_write_bytes_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]:
        """Calculate write memory traffic for FFN layers."""
        L, D, DI = self.num_hidden_layers, self.hidden_size, self.intermediate_size
        Lm, E, MI, S = (
            self.num_moe_layers,
            self.num_experts_per_tok,
            self.moe_intermediate_size,
            self.num_shared_experts,
        )
        T = ctx.total_num_tokens()

        Ld = L - Lm

        num_activated_tokens = T * E if E else 0

        if per_gpu:
            Ld //= self.pp_size
            Lm //= self.pp_size

            DI //= self.ffn_tp_size
            if MI is not None:
                MI //= self.ffn_tp_size
            if E:
                num_activated_tokens //= self.ffn_ep_size

        write_bytes = {}

        # Dense FFN layers
        if Ld:
            write_bytes["dense_up_gate_output"] = int(
                2 * T * DI * self.activation_byte_size * Ld
            )
            write_bytes["dense_silu_output"] = int(
                T * DI * self.activation_byte_size * Ld
            )
            write_bytes["dense_down_output"] = int(
                T * D * self.activation_byte_size * Ld
            )

        # MoE outputs
        if Lm:
            if E:
                write_bytes["routed_up_gate_output"] = int(
                    2 * num_activated_tokens * MI * self.activation_byte_size * Lm
                )
                write_bytes["routed_silu_output"] = int(
                    num_activated_tokens * MI * self.activation_byte_size * Lm
                )
                write_bytes["routed_down_output"] = int(
                    num_activated_tokens * D * self.activation_byte_size * Lm
                )
            if S:
                write_bytes["shared_up_gate_output"] = int(
                    2 * T * S * MI * self.activation_byte_size * Lm
                )
                write_bytes["shared_silu_output"] = int(
                    T * S * MI * self.activation_byte_size * Lm
                )
                write_bytes["shared_down_output"] = int(
                    T * S * D * self.activation_byte_size * Lm
                )

        return write_bytes


#### Unembed ####


class UnembedMetrics(ComponentMetrics):
    # From BaseConfigParser
    hidden_size: int = Field(..., gt=0)
    vocab_size: int = Field(..., gt=0)
    weight_byte_size: int = Field(..., gt=0)
    activation_byte_size: int = Field(..., gt=0)

    tp_size: int

    @classmethod
    def component_type(cls) -> str:
        return "unembed"

    @classmethod
    def get_parser(cls) -> ParserChain:
        return ParserChain(
            BaseConfigParser(),
        )

    def get_num_flops_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]:
        """Calculate flops breakdown for unembedding layer."""
        D, V = self.hidden_size, self.vocab_size
        T = ctx.num_logits_tokens()

        if per_gpu:
            V //= self.tp_size

        return {
            "unembed": 2 * T * D * V,
        }

    def get_read_bytes_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]:
        """Calculate read memory traffic for unembedding layer."""
        D, V = self.hidden_size, self.vocab_size
        T = ctx.num_logits_tokens()

        if per_gpu:
            V //= self.tp_size

        return {
            "input": T * D * self.activation_byte_size,
            "weight": D * V * self.weight_byte_size,
        }

    def get_write_bytes_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]:
        """Calculate write memory traffic for unembedding layer."""
        V = self.vocab_size
        T = ctx.num_logits_tokens()

        if per_gpu:
            V //= self.tp_size

        return {
            "output": T * V * self.activation_byte_size,
        }


#### ModelMetrics ####


class ModelMetrics:
    def __init__(self, vllm_config: VllmConfig) -> None:
        """
        Parse vllm_config to instantiate metrics for each component.
        is_enabled() will return False if no component metrics could be instantiated.
        """

        self.vllm_config = vllm_config

        self.metrics: list[ComponentMetrics] = []
        for metric_cls in ComponentMetrics.registered_metrics():
            try:
                metric = metric_cls.from_vllm_config(vllm_config)
                self.metrics.append(metric)
                logger.info(
                    "Instantiated ComponentMetrics [%s] with (%s)",
                    metric.component_type(),
                    str(metric),
                )
            except InvalidComponent as e:
                logger.debug(
                    "Failed to instantiate %s from %s",
                    metric_cls.component_type(),
                    str(e),
                )

    def is_enabled(self) -> bool:
        return len(self.metrics) > 0

    def get_num_flops(self, ctx: ExecutionContext, per_gpu: bool = True) -> int:
        return sum(metric.get_num_flops(ctx, per_gpu) for metric in self.metrics)

    def get_read_bytes(self, ctx: ExecutionContext, per_gpu: bool = True) -> int:
        return sum(metric.get_read_bytes(ctx, per_gpu) for metric in self.metrics)

    def get_write_bytes(self, ctx: ExecutionContext, per_gpu: bool = True) -> int:
        return sum(metric.get_write_bytes(ctx, per_gpu) for metric in self.metrics)

    def get_num_flops_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]:
        total = {}
        for metric in self.metrics:
            breakdown = metric.get_num_flops_breakdown(ctx, per_gpu)
            component = metric.component_type()
            prefixed = {f"{component}.{key}": val for key, val in breakdown.items()}
            total.update(prefixed)
        return total

    def get_read_bytes_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]:
        total = {}
        for metric in self.metrics:
            breakdown = metric.get_read_bytes_breakdown(ctx, per_gpu)
            component = metric.component_type()
            prefixed = {f"{component}.{key}": val for key, val in breakdown.items()}
            total.update(prefixed)
        return total

    def get_write_bytes_breakdown(
        self, ctx: ExecutionContext, per_gpu: bool = True
    ) -> dict[str, int]:
        total = {}
        for metric in self.metrics:
            breakdown = metric.get_write_bytes_breakdown(ctx, per_gpu)
            component = metric.component_type()
            prefixed = {f"{component}.{key}": val for key, val in breakdown.items()}
            total.update(prefixed)
        return total

    def get_step_perf_stats_per_gpu(
        self, scheduler_output: SchedulerOutput
    ) -> PerfStats:
        """
        Calculate perf stats for the current step based on scheduled tokens.
        """

        t0 = time.monotonic()

        # Build a single batch context
        ctx = ExecutionContext()

        # Process new requests (these are in prefill phase)
        for new_req in scheduler_output.scheduled_new_reqs:
            req_id = new_req.req_id
            num_tokens = scheduler_output.num_scheduled_tokens.get(req_id, 0)
            if num_tokens == 0:
                continue

            # For new requests, context_len = num_computed_tokens + num_tokens
            # num_computed_tokens represents previously computed tokens in the sequence
            context_len = new_req.num_computed_tokens + num_tokens
            ctx.add(num_tokens, context_len, is_prefill=True)

        # Process cached requests (continuing requests)
        cached_reqs = scheduler_output.scheduled_cached_reqs
        for i, req_id in enumerate(cached_reqs.req_ids):
            num_tokens = scheduler_output.num_scheduled_tokens.get(req_id, 0)
            if num_tokens == 0:
                continue

            # For cached requests, we have the current num_computed_tokens
            num_computed_tokens = cached_reqs.num_computed_tokens[i]
            context_len = num_computed_tokens + num_tokens

            # Cached requests are typically in decode phase (num_tokens == 1)
            # unless they're doing chunked prefill (num_tokens > 1)
            is_prefill = num_tokens > 1
            ctx.add(num_tokens, context_len, is_prefill)

        num_flops_breakdown = self.get_num_flops_breakdown(ctx, True)
        read_bytes_breakdown = self.get_read_bytes_breakdown(ctx, True)
        write_bytes_breakdown = self.get_write_bytes_breakdown(ctx, True)
        perf_stats = PerfStats(
            sum(num_flops_breakdown.values()),
            sum(read_bytes_breakdown.values()),
            sum(write_bytes_breakdown.values()),
        )

        if envs.VLLM_DEBUG_MFU_METRICS:
            perf_stats.debug_stats = DebugPerfStats(
                time.monotonic() - t0,
                ctx.num_prefill_requests,
                ctx.num_decode_requests,
                asdict(ctx),
                num_flops_breakdown,
                read_bytes_breakdown,
                write_bytes_breakdown,
            )

        return perf_stats


#### Logging ####


class PerfMetricsDebugLogging:
    def __init__(self):
        self.reset()

    def reset(self):
        self.total_calc_duration: float = 0.0
        self.total_num_prefill_requests: int = 0
        self.total_num_decode_requests: int = 0
        self.total_num_batches: int = 0
        self.total_context_breakdown: dict[str, int] = {}
        self.total_num_flops_per_gpu_breakdown: dict[str, int] = {}
        self.total_read_bytes_per_gpu_breakdown: dict[str, int] = {}
        self.total_write_bytes_per_gpu_breakdown: dict[str, int] = {}

    def observe(self, debug_stats: DebugPerfStats) -> None:
        self.total_calc_duration += debug_stats.calc_duration
        self.total_num_prefill_requests += debug_stats.num_prefill_requests
        self.total_num_decode_requests += debug_stats.num_decode_requests
        self.total_num_batches += 1

        for dst, src in zip(
            [
                self.total_context_breakdown,
                self.total_num_flops_per_gpu_breakdown,
                self.total_read_bytes_per_gpu_breakdown,
                self.total_write_bytes_per_gpu_breakdown,
            ],
            [
                debug_stats.context_breakdown,
                debug_stats.num_flops_per_gpu_breakdown,
                debug_stats.num_read_bytes_per_gpu_breakdown,
                debug_stats.num_write_bytes_per_gpu_breakdown,
            ],
        ):
            assert isinstance(src, dict)
            for key, val in src.items():
                dst[key] = dst.get(key, 0) + val

    def log(self, log_fn, log_prefix: str, delta_time: float):
        # pretty print breakdowns
        total_num_flops_per_gpu_breakdown = {
            k: f"{v / 1e12:.1f}TF"
            for k, v in self.total_num_flops_per_gpu_breakdown.items()
        }
        total_read_bytes_per_gpu_breakdown = {
            k: f"{v / 1e9:.1f}GB"
            for k, v in self.total_read_bytes_per_gpu_breakdown.items()
        }
        total_write_bytes_per_gpu_breakdown = {
            k: f"{v / 1e9:.1f}GB"
            for k, v in self.total_write_bytes_per_gpu_breakdown.items()
        }

        logger.debug(
            "%sMFU details: %s",
            log_prefix,
            json.dumps(
                {
                    "prefill_reqs": self.total_num_prefill_requests,
                    "decode_reqs": self.total_num_decode_requests,
                    "num_batches": self.total_num_batches,
                    "context_breakdown": self.total_context_breakdown,
                    "flops_breakdown": total_num_flops_per_gpu_breakdown,
                    "num_read_bytes_breakdown": total_read_bytes_per_gpu_breakdown,
                    "num_write_bytes_breakdown": (total_write_bytes_per_gpu_breakdown),
                    "duration": f"{delta_time:.1f}s",
                    "mfu_calc_overhead": (
                        f"{self.total_calc_duration / delta_time:.1%}"
                    ),
                },
                indent=2,
            ),
        )


class PerfMetricsLogging:
    def __init__(self, vllm_config: VllmConfig):
        self.vllm_config = vllm_config
        self.pp_size = vllm_config.parallel_config.pipeline_parallel_size

        self.debug_logging: PerfMetricsDebugLogging | None = None
        if envs.VLLM_DEBUG_MFU_METRICS:
            self.debug_logging = PerfMetricsDebugLogging()

        self.reset()

    def reset(self):
        self.last_log_time = time.monotonic()

        self.total_num_flops_per_gpu: int = 0
        self.total_read_bytes_per_gpu: int = 0
        self.total_write_bytes_per_gpu: int = 0

        if self.debug_logging:
            self.debug_logging.reset()

    def observe(self, perf_stats: PerfStats) -> None:
        self.total_num_flops_per_gpu += perf_stats.num_flops_per_gpu
        self.total_read_bytes_per_gpu += perf_stats.num_read_bytes_per_gpu
        self.total_write_bytes_per_gpu += perf_stats.num_write_bytes_per_gpu

        if self.debug_logging:
            assert perf_stats.debug_stats is not None
            self.debug_logging.observe(perf_stats.debug_stats)

    def log(self, log_fn=logger.info, log_prefix: str = "") -> None:
        if not (
            self.total_num_flops_per_gpu
            or self.total_read_bytes_per_gpu
            or self.total_write_bytes_per_gpu
        ):
            return

        now = time.monotonic()
        delta_time = now - self.last_log_time

        if delta_time <= 0.0:
            avg_tflops_per_gpu = 0.0
            avg_gbps_per_gpu = 0.0
        else:
            avg_tflops_per_gpu = self.total_num_flops_per_gpu / delta_time / 1e12
            avg_gbps_per_gpu = (
                (self.total_read_bytes_per_gpu + self.total_write_bytes_per_gpu)
                / delta_time
                / 1e9
            )

        log_fn(
            "%sMFU: %.1f TF/s/GPU %.1f GB/s/GPU",
            log_prefix,
            avg_tflops_per_gpu,
            avg_gbps_per_gpu,
        )

        if self.debug_logging:
            self.debug_logging.log(log_fn, log_prefix, delta_time)

        self.reset()


## util functions


def get_required(obj: object, attr: str):
    """Get an attr from an object, or throw a InvalidComponentError if it's not set."""
    if not hasattr(obj, attr):
        raise InvalidComponent(f"Missing required attr {attr} in config")
    return getattr(obj, attr)


def getattr_from_list(obj: object, attrs: list[str], default: object = None):
    """Try to get the first attr that exists in the object
    from a list of attrs. Otherwise return None."""
    for attr in attrs:
        if hasattr(obj, attr):
            return getattr(obj, attr)
    return default