Function metric_tags 

pub fn metric_tags(metric: &CtprofMetricDef) -> String

Render a metric’s bracketed gating tags as a single space-separated string. Returns the empty string when sched_class is None, is_dead is false, AND config_gates is empty.

Tag emission order: [<sched_class>] first when sched_class is Some, then [dead] when is_dead, then each config_gate in registry-declared order. Examples:

• nr_wakeups_affine → [cfs-only] [SCHEDSTATS]
• core_forceidle_sum → [SCHED_CORE] [SCHEDSTATS]
• fair_slice_ns → [fair-policy]

Compact rendering: each config_gate is stripped of its CONFIG_ prefix before emission so the rendered cell stays scannable in narrow tables. The data field CtprofMetricDef::config_gates keeps the full CONFIG_X spelling so an operator can grep their kconfig directly. sched_class tags are rendered as-is (already short, e.g. [cfs-only], [fair-policy], [non-ext]).

Pure formatting layer — does not interpret tag values; the metric’s own CtprofMetricDef::sched_class / CtprofMetricDef::config_gates / CtprofMetricDef::is_dead docs are the source of truth for what each spelling means.