Derive Macro Payload 

#[derive(Payload)]
{
    // Attributes available to this derive:
    #[payload]
    #[default_args]
    #[default_check]
    #[metric]
    #[include_files]
}

Derive macro that generates a Payload const from an annotated struct for a userspace binary workload (stress-ng, fio, and similar tools test authors compose under a scheduler).

Required struct-level attributes (#[payload(...)])

• binary = "..." — the binary name resolved by the guest’s include-files infrastructure (required). Becomes PayloadKind::Binary(name) (ktstr::test_support::PayloadKind::Binary), and is also auto-prepended to the emitted include_files slice so the binary is packaged into the initramfs without needing a separate #[include_files("...")] entry. Extra auxiliary files (helpers, configs, fixtures) still go on #[include_files(...)].

Optional struct-level attributes

• name = "..." — short name used in logs and sidecar records. Defaults to the binary name.
• output = Json | ExitCode — how the framework extracts metrics from the payload’s stdout. The variant names match the OutputFormat enum and the Polarity kwarg grammar. Defaults to ExitCode.

Optional outer attributes

• #[default_args("--a", "--b", ...)] — variadic string literals appended to the binary’s argv when the payload runs. May repeat across multiple #[default_args(...)] attrs; entries accumulate in source order.
• #[default_check(...)] — one MetricCheck (ktstr::test_support::MetricCheck) construction expression (e.g. min("iops", 1000.0), exit_code_eq(0)). May repeat; entries accumulate in source order. Both min(...) and MetricCheck::min(...) are accepted: the macro prepends ::ktstr::test_support::MetricCheck:: when the expression doesn’t already spell MetricCheck:: on its callee path, so bare constructors work without an import and qualified constructors read naturally in modules that already have MetricCheck in scope.
• #[metric(name = "...", polarity = ..., unit = "...")] — kwarg form. polarity is one of HigherBetter, LowerBetter, TargetValue(f64), Unknown. May repeat; entries accumulate.
• #[include_files("helper", "config.json", ...)] — variadic string literals appended to the emitted include_files slice after the auto-injected binary entry. Each entry passes through the same resolver used by the CLI -i flag (bare names search host PATH; explicit paths must exist; directories are walked). The primary binary is already packaged automatically, so this attribute is only needed for auxiliary files the payload depends on.

Const name derivation

Strip trailing "Payload" suffix (if present), then convert to SCREAMING_SNAKE_CASE. FioPayload → FIO, StressNgPayload → STRESS_NG, Fio (no suffix) → FIO.

Example

use ktstr::prelude::*;

#[derive(Payload)]
#[payload(binary = "fio", output = Json)]
#[default_args("--output-format=json", "--minimal")]
#[default_check(exit_code_eq(0))]
#[metric(name = "jobs.0.read.iops", polarity = HigherBetter, unit = "iops")]
struct FioPayload;