GOGC
The GOGC variable sets the initial 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.
Default Value
The default is GOGC=100, which means garbage collection will not be triggered until the heap has grown by 100% since the previous collection. Effectively GOGC=100 (the default) means the garbage collector will run each time the live heap doubles.
- Setting this value higher, say
GOGC=200, will delay the start of a garbage collection cycle until the live heap has grown to 200% of the previous size. - Setting the value lower, say
GOGC=20will cause the garbage collector to be triggered more often as less new data can be allocated on the heap before triggering a collection.
Setting GOGC=off disables the garbage collector entirely. The runtime/debug package’s SetGCPercent function allows changing this percentage at run time. See https://golang.org/pkg/runtime/debug/#SetGCPercent.
// NextGC is the target heap size of the next GC cycle.
//
// The garbage collector's goal is to keep HeapAlloc ≤ NextGC.
// At the end of each GC cycle, the target for the next cycle
// is computed based on the amount of reachable data and the
// value of GOGC.
NextGC uint64
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.
GOMAXPROCS()
func GOMAXPROCS(n int) int
GOMAXPROCS sets the maximum number of logical processors (M-P-G model) that can be executing simultaneously and returns the previous setting. It defaults to the value of runtime.NumCPU. If n < 1, it does not change the current setting. This call will go away when the scheduler improves.
NumCPU()
func NumCPU() int
NumCPU returns the number of logical CPUs usable by the current process.
The set of available CPUs is checked by querying the operating system at process startup. Changes to operating system CPU allocation after process startup are not reflected.