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Overview ¶
Package gctune centralizes the process-wide GC knobs that the rest of the runtime deliberately refuses to touch. It is the single place allowed to flip a global runtime setting (GOGC, the soft memory limit) so the dangerous mutation lives behind a small, audited API rather than scattered `runtime/debug` calls.
It complements compiler/debug, which only *reads* GC/heap stats and explicitly leaves the mutating knobs "at the caller's risk". gctune is that caller.
Two consumers use it:
- cmd (host-side perf flags: -gc-percent, -mem-limit), applied once at startup via Apply.
- the Lua `collectgarbage` builtin (vm/stdlib.go), which maps Lua's option strings onto Collect/Stop/Restart/SetPercent/HeapBytes.
All mutating entry points are guarded by a single mutex and share package state, matching the fact that Go has exactly one collector per process.
Index ¶
Constants ¶
const DefaultPercent = 100
DefaultPercent mirrors Go's default GOGC. Restart and the "remembered" percent fall back to it when GC has never been explicitly configured.
Variables ¶
This section is empty.
Functions ¶
func Apply ¶
func Apply(o Options)
Apply installs the requested knobs. Intended to be called once, early, from the host (cmd) before any script runs.
func HeapBytes ¶
func HeapBytes() uint64
HeapBytes returns the bytes of live heap objects currently allocated. Backs collectgarbage("count"). Note: ReadMemStats briefly stops the world, so this is a reporting call, not a hot-path metric.
func IsRunning ¶
func IsRunning() bool
IsRunning reports whether the collector is currently enabled. Backs collectgarbage("isrunning").
func Restart ¶
func Restart()
Restart re-enables the collector at the last enabled percent. Backs collectgarbage("restart").
func SetMemoryLimit ¶
SetMemoryLimit sets the soft heap limit in bytes and returns the previous limit. Passing a negative value queries the current limit without changing it (the runtime/debug contract).
func SetPercent ¶
SetPercent sets GOGC and returns the previous value. A negative pct disables the GC (and is not remembered as the restart target). Backs collectgarbage("setpause", n).
Types ¶
type Options ¶
type Options struct {
// Percent sets GOGC. Zero leaves it at the current value; a negative value
// disables the GC entirely (equivalent to collectgarbage("stop")).
Percent int
// MemoryLimit sets the soft heap limit in bytes. Zero leaves the current
// limit untouched.
MemoryLimit int64
}
Options configures the process GC at startup. A zero field leaves that knob untouched, so callers can pass only what they want to override.
Source Files