debug

Documentation

Overview

Package debug contains facilities for programs to debug themselves while they are running.

Index

• func FreeOSMemory()
• func PrintStack()
• func ReadGCStats(stats *GCStats)
• func SetGCPercent(percent int) int
• func SetMaxStack(bytes int) int
• func SetMaxThreads(threads int) int
• func Stack() []byte
• type GCStats

Functions

func FreeOSMemory

func FreeOSMemory()

FreeOSMemory forces a garbage collection followed by an attempt to return as much memory to the operating system as possible. (Even if this is not called, the runtime gradually returns memory to the operating system in a background task.)

func PrintStack

func PrintStack()

PrintStack prints to standard error the stack trace returned by Stack.

func ReadGCStats

func ReadGCStats(stats *GCStats)

ReadGCStats reads statistics about garbage collection into stats. The number of entries in the pause history is system-dependent; stats.Pause slice will be reused if large enough, reallocated otherwise. ReadGCStats may use the full capacity of the stats.Pause slice. If stats.PauseQuantiles is non-empty, ReadGCStats fills it with quantiles summarizing the distribution of pause time. For example, if len(stats.PauseQuantiles) is 5, it will be filled with the minimum, 25%, 50%, 75%, and maximum pause times.

func SetGCPercent

func SetGCPercent(percent int) int

SetGCPercent sets the garbage collection target percentage: a collection is triggered when the ratio of freshly allocated data to live data remaining after the previous collection reaches this percentage. SetGCPercent returns the previous setting. The initial setting is the value of the GOGC environment variable at startup, or 100 if the variable is not set. A negative percentage disables garbage collection.

func SetMaxStack

func SetMaxStack(bytes int) int

SetMaxStack sets the maximum amount of memory that can be used by a single goroutine stack. If any goroutine exceeds this limit while growing its stack, the program crashes. SetMaxStack returns the previous setting. The initial setting is 1 GB on 64-bit systems, 250 MB on 32-bit systems.

SetMaxStack is useful mainly for limiting the damage done by goroutines that enter an infinite recursion. It only limits future stack growth.

func SetMaxThreads

func SetMaxThreads(threads int) int

SetMaxThreads sets the maximum number of operating system threads that the Go program can use. If it attempts to use more than this many, the program crashes. SetMaxThreads returns the previous setting. The initial setting is 10,000 threads.

The limit controls the number of operating system threads, not the number of goroutines. A Go program creates a new thread only when a goroutine is ready to run but all the existing threads are blocked in system calls, cgo calls, or are locked to other goroutines due to use of runtime.LockOSThread.

SetMaxThreads is useful mainly for limiting the damage done by programs that create an unbounded number of threads. The idea is to take down the program before it takes down the operating system.

func Stack

func Stack() []byte

Stack returns a formatted stack trace of the goroutine that calls it. For each routine, it includes the source line information and PC value, then attempts to discover, for Go functions, the calling function or method and the text of the line containing the invocation.

This function is deprecated. Use package runtime's Stack instead.

Types

type GCStats

type GCStats struct {
	LastGC         time.Time       // time of last collection
	NumGC          int64           // number of garbage collections
	PauseTotal     time.Duration   // total pause for all collections
	Pause          []time.Duration // pause history, most recent first
	PauseQuantiles []time.Duration
}

GCStats collect information about recent garbage collections.