src/runtime/metrics/doc.go - go - Git at Google

 // Copyright 2020 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 /*
 Package metrics provides a stable interface to access implementation-defined
 metrics exported by the Go runtime. This package is similar to existing functions
 like runtime.ReadMemStats and debug.ReadGCStats, but significantly more general.

 The set of metrics defined by this package may evolve as the runtime itself
 evolves, and also enables variation across Go implementations, whose relevant
 metric sets may not intersect.

 # Interface

 Metrics are designated by a string key, rather than, for example, a field name in
 a struct. The full list of supported metrics is always available in the slice of
 Descriptions returned by All. Each Description also includes useful information
 about the metric.

 Thus, users of this API are encouraged to sample supported metrics defined by the
 slice returned by All to remain compatible across Go versions. Of course, situations
 arise where reading specific metrics is critical. For these cases, users are
 encouraged to use build tags, and although metrics may be deprecated and removed,
 users should consider this to be an exceptional and rare event, coinciding with a
 very large change in a particular Go implementation.

 Each metric key also has a "kind" that describes the format of the metric's value.
 In the interest of not breaking users of this package, the "kind" for a given metric
 is guaranteed not to change. If it must change, then a new metric will be introduced
 with a new key and a new "kind."

 # Metric key format

 As mentioned earlier, metric keys are strings. Their format is simple and well-defined,
 designed to be both human and machine readable. It is split into two components,
 separated by a colon: a rooted path and a unit. The choice to include the unit in
 the key is motivated by compatibility: if a metric's unit changes, its semantics likely
 did also, and a new key should be introduced.

 For more details on the precise definition of the metric key's path and unit formats, see
 the documentation of the Name field of the Description struct.

 # A note about floats

 This package supports metrics whose values have a floating-point representation. In
 order to improve ease-of-use, this package promises to never produce the following
 classes of floating-point values: NaN, infinity.

 # Supported metrics

 Below is the full list of supported metrics, ordered lexicographically.

 	/cgo/go-to-c-calls:calls
 		Count of calls made from Go to C by the current process.

 	/cpu/classes/gc/mark/assist:cpu-seconds
 		Estimated total CPU time goroutines spent performing GC tasks
 		to assist the GC and prevent it from falling behind the application.
 		This metric is an overestimate, and not directly comparable to
 		system CPU time measurements. Compare only with other /cpu/classes
 		metrics.

 	/cpu/classes/gc/mark/dedicated:cpu-seconds
 		Estimated total CPU time spent performing GC tasks on
 		processors (as defined by GOMAXPROCS) dedicated to those tasks.
 		This includes time spent with the world stopped due to the GC.
 		This metric is an overestimate, and not directly comparable to
 		system CPU time measurements. Compare only with other /cpu/classes
 		metrics.

 	/cpu/classes/gc/mark/idle:cpu-seconds
 		Estimated total CPU time spent performing GC tasks on
 		spare CPU resources that the Go scheduler could not otherwise find
 		a use for. This should be subtracted from the total GC CPU time to
 		obtain a measure of compulsory GC CPU time.
 		This metric is an overestimate, and not directly comparable to
 		system CPU time measurements. Compare only with other /cpu/classes
 		metrics.

 	/cpu/classes/gc/pause:cpu-seconds
 		Estimated total CPU time spent with the application paused by
 		the GC. Even if only one thread is running during the pause, this is
 		computed as GOMAXPROCS times the pause latency because nothing else
 		can be executing. This is the exact sum of samples in /gc/pause:seconds
 		if each sample is multiplied by GOMAXPROCS at the time it is taken.
 		This metric is an overestimate, and not directly comparable to
 		system CPU time measurements. Compare only with other /cpu/classes
 		metrics.

 	/cpu/classes/gc/total:cpu-seconds
 		Estimated total CPU time spent performing GC tasks.
 		This metric is an overestimate, and not directly comparable to
 		system CPU time measurements. Compare only with other /cpu/classes
 		metrics. Sum of all metrics in /cpu/classes/gc.

 	/cpu/classes/idle:cpu-seconds
 		Estimated total available CPU time not spent executing any Go or Go
 		runtime code. In other words, the part of /cpu/classes/total:cpu-seconds
 		that was unused.
 		This metric is an overestimate, and not directly comparable to
 		system CPU time measurements. Compare only with other /cpu/classes
 		metrics.

 	/cpu/classes/scavenge/assist:cpu-seconds
 		Estimated total CPU time spent returning unused memory to the
 		underlying platform in response eagerly in response to memory pressure.
 		This metric is an overestimate, and not directly comparable to
 		system CPU time measurements. Compare only with other /cpu/classes
 		metrics.

 	/cpu/classes/scavenge/background:cpu-seconds
 		Estimated total CPU time spent performing background tasks
 		to return unused memory to the underlying platform.
 		This metric is an overestimate, and not directly comparable to
 		system CPU time measurements. Compare only with other /cpu/classes
 		metrics.

 	/cpu/classes/scavenge/total:cpu-seconds
 		Estimated total CPU time spent performing tasks that return
 		unused memory to the underlying platform.
 		This metric is an overestimate, and not directly comparable to
 		system CPU time measurements. Compare only with other /cpu/classes
 		metrics. Sum of all metrics in /cpu/classes/scavenge.

 	/cpu/classes/total:cpu-seconds
 		Estimated total available CPU time for user Go code or the Go runtime, as
 		defined by GOMAXPROCS. In other words, GOMAXPROCS integrated over the
 		wall-clock duration this process has been executing for.
 		This metric is an overestimate, and not directly comparable to
 		system CPU time measurements. Compare only with other /cpu/classes
 		metrics. Sum of all metrics in /cpu/classes.

 	/cpu/classes/user:cpu-seconds
 		Estimated total CPU time spent running user Go code. This may
 		also include some small amount of time spent in the Go runtime.
 		This metric is an overestimate, and not directly comparable to
 		system CPU time measurements. Compare only with other /cpu/classes
 		metrics.

 	/gc/cycles/automatic:gc-cycles
 		Count of completed GC cycles generated by the Go runtime.

 	/gc/cycles/forced:gc-cycles
 		Count of completed GC cycles forced by the application.

 	/gc/cycles/total:gc-cycles
 		Count of all completed GC cycles.

 	/gc/heap/allocs-by-size:bytes
 		Distribution of heap allocations by approximate size.
 		Note that this does not include tiny objects as defined by /gc/heap/tiny/allocs:objects,
 		only tiny blocks.

 	/gc/heap/allocs:bytes
 		Cumulative sum of memory allocated to the heap by the application.

 	/gc/heap/allocs:objects
 		Cumulative count of heap allocations triggered by the application.
 		Note that this does not include tiny objects as defined by /gc/heap/tiny/allocs:objects,
 		only tiny blocks.

 	/gc/heap/frees-by-size:bytes
 		Distribution of freed heap allocations by approximate size.
 		Note that this does not include tiny objects as defined by /gc/heap/tiny/allocs:objects,
 		only tiny blocks.

 	/gc/heap/frees:bytes
 		Cumulative sum of heap memory freed by the garbage collector.

 	/gc/heap/frees:objects
 		Cumulative count of heap allocations whose storage was freed by the garbage collector.
 		Note that this does not include tiny objects as defined by /gc/heap/tiny/allocs:objects,
 		only tiny blocks.

 	/gc/heap/goal:bytes
 		Heap size target for the end of the GC cycle.

 	/gc/heap/objects:objects
 		Number of objects, live or unswept, occupying heap memory.

 	/gc/heap/tiny/allocs:objects
 		Count of small allocations that are packed together into blocks.
 		These allocations are counted separately from other allocations
 		because each individual allocation is not tracked by the runtime,
 		only their block. Each block is already accounted for in
 		allocs-by-size and frees-by-size.

 	/gc/limiter/last-enabled:gc-cycle
 		GC cycle the last time the GC CPU limiter was enabled.
 		This metric is useful for diagnosing the root cause of an out-of-memory
 		error, because the limiter trades memory for CPU time when the GC's CPU
 		time gets too high. This is most likely to occur with use of SetMemoryLimit.
 		The first GC cycle is cycle 1, so a value of 0 indicates that it was never enabled.

 	/gc/pauses:seconds
 		Distribution individual GC-related stop-the-world pause latencies.

 	/gc/stack/starting-size:bytes
 		The stack size of new goroutines.

 	/memory/classes/heap/free:bytes
 		Memory that is completely free and eligible to be returned to
 		the underlying system, but has not been. This metric is the
 		runtime's estimate of free address space that is backed by
 		physical memory.

 	/memory/classes/heap/objects:bytes
 		Memory occupied by live objects and dead objects that have
 		not yet been marked free by the garbage collector.

 	/memory/classes/heap/released:bytes
 		Memory that is completely free and has been returned to
 		the underlying system. This metric is the runtime's estimate of
 		free address space that is still mapped into the process, but
 		is not backed by physical memory.

 	/memory/classes/heap/stacks:bytes
 		Memory allocated from the heap that is reserved for stack
 		space, whether or not it is currently in-use.

 	/memory/classes/heap/unused:bytes
 		Memory that is reserved for heap objects but is not currently
 		used to hold heap objects.

 	/memory/classes/metadata/mcache/free:bytes
 		Memory that is reserved for runtime mcache structures, but
 		not in-use.

 	/memory/classes/metadata/mcache/inuse:bytes
 		Memory that is occupied by runtime mcache structures that
 		are currently being used.

 	/memory/classes/metadata/mspan/free:bytes
 		Memory that is reserved for runtime mspan structures, but
 		not in-use.

 	/memory/classes/metadata/mspan/inuse:bytes
 		Memory that is occupied by runtime mspan structures that are
 		currently being used.

 	/memory/classes/metadata/other:bytes
 		Memory that is reserved for or used to hold runtime
 		metadata.

 	/memory/classes/os-stacks:bytes
 		Stack memory allocated by the underlying operating system.

 	/memory/classes/other:bytes
 		Memory used by execution trace buffers, structures for
 		debugging the runtime, finalizer and profiler specials, and
 		more.

 	/memory/classes/profiling/buckets:bytes
 		Memory that is used by the stack trace hash map used for
 		profiling.

 	/memory/classes/total:bytes
 		All memory mapped by the Go runtime into the current process
 		as read-write. Note that this does not include memory mapped
 		by code called via cgo or via the syscall package.
 		Sum of all metrics in /memory/classes.

 	/sched/gomaxprocs:threads
 		The current runtime.GOMAXPROCS setting, or the number of
 		operating system threads that can execute user-level Go code
 		simultaneously.

 	/sched/goroutines:goroutines
 		Count of live goroutines.

 	/sched/latencies:seconds
 		Distribution of the time goroutines have spent in the scheduler
 		in a runnable state before actually running.

 	/sync/mutex/wait/total:seconds
 		Approximate cumulative time goroutines have spent blocked on a
 		sync.Mutex or sync.RWMutex. This metric is useful for identifying
 		global changes in lock contention. Collect a mutex or block
 		profile using the runtime/pprof package for more detailed
 		contention data.
 */
 package metrics
	// Copyright 2020 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	/*
	Package metrics provides a stable interface to access implementation-defined
	metrics exported by the Go runtime. This package is similar to existing functions
	like runtime.ReadMemStats and debug.ReadGCStats, but significantly more general.

	The set of metrics defined by this package may evolve as the runtime itself
	evolves, and also enables variation across Go implementations, whose relevant
	metric sets may not intersect.

	# Interface

	Metrics are designated by a string key, rather than, for example, a field name in
	a struct. The full list of supported metrics is always available in the slice of
	Descriptions returned by All. Each Description also includes useful information
	about the metric.

	Thus, users of this API are encouraged to sample supported metrics defined by the
	slice returned by All to remain compatible across Go versions. Of course, situations
	arise where reading specific metrics is critical. For these cases, users are
	encouraged to use build tags, and although metrics may be deprecated and removed,
	users should consider this to be an exceptional and rare event, coinciding with a
	very large change in a particular Go implementation.

	Each metric key also has a "kind" that describes the format of the metric's value.
	In the interest of not breaking users of this package, the "kind" for a given metric
	is guaranteed not to change. If it must change, then a new metric will be introduced
	with a new key and a new "kind."

	# Metric key format

	As mentioned earlier, metric keys are strings. Their format is simple and well-defined,
	designed to be both human and machine readable. It is split into two components,
	separated by a colon: a rooted path and a unit. The choice to include the unit in
	the key is motivated by compatibility: if a metric's unit changes, its semantics likely
	did also, and a new key should be introduced.

	For more details on the precise definition of the metric key's path and unit formats, see
	the documentation of the Name field of the Description struct.

	# A note about floats

	This package supports metrics whose values have a floating-point representation. In
	order to improve ease-of-use, this package promises to never produce the following
	classes of floating-point values: NaN, infinity.

	# Supported metrics

	Below is the full list of supported metrics, ordered lexicographically.

	/cgo/go-to-c-calls:calls
	Count of calls made from Go to C by the current process.

	/cpu/classes/gc/mark/assist:cpu-seconds
	Estimated total CPU time goroutines spent performing GC tasks
	to assist the GC and prevent it from falling behind the application.
	This metric is an overestimate, and not directly comparable to
	system CPU time measurements. Compare only with other /cpu/classes
	metrics.

	/cpu/classes/gc/mark/dedicated:cpu-seconds
	Estimated total CPU time spent performing GC tasks on
	processors (as defined by GOMAXPROCS) dedicated to those tasks.
	This includes time spent with the world stopped due to the GC.
	This metric is an overestimate, and not directly comparable to
	system CPU time measurements. Compare only with other /cpu/classes
	metrics.

	/cpu/classes/gc/mark/idle:cpu-seconds
	Estimated total CPU time spent performing GC tasks on
	spare CPU resources that the Go scheduler could not otherwise find
	a use for. This should be subtracted from the total GC CPU time to
	obtain a measure of compulsory GC CPU time.
	This metric is an overestimate, and not directly comparable to
	system CPU time measurements. Compare only with other /cpu/classes
	metrics.

	/cpu/classes/gc/pause:cpu-seconds
	Estimated total CPU time spent with the application paused by
	the GC. Even if only one thread is running during the pause, this is
	computed as GOMAXPROCS times the pause latency because nothing else
	can be executing. This is the exact sum of samples in /gc/pause:seconds
	if each sample is multiplied by GOMAXPROCS at the time it is taken.
	This metric is an overestimate, and not directly comparable to
	system CPU time measurements. Compare only with other /cpu/classes
	metrics.

	/cpu/classes/gc/total:cpu-seconds
	Estimated total CPU time spent performing GC tasks.
	This metric is an overestimate, and not directly comparable to
	system CPU time measurements. Compare only with other /cpu/classes
	metrics. Sum of all metrics in /cpu/classes/gc.

	/cpu/classes/idle:cpu-seconds
	Estimated total available CPU time not spent executing any Go or Go
	runtime code. In other words, the part of /cpu/classes/total:cpu-seconds
	that was unused.
	This metric is an overestimate, and not directly comparable to
	system CPU time measurements. Compare only with other /cpu/classes
	metrics.

	/cpu/classes/scavenge/assist:cpu-seconds
	Estimated total CPU time spent returning unused memory to the
	underlying platform in response eagerly in response to memory pressure.
	This metric is an overestimate, and not directly comparable to
	system CPU time measurements. Compare only with other /cpu/classes
	metrics.

	/cpu/classes/scavenge/background:cpu-seconds
	Estimated total CPU time spent performing background tasks
	to return unused memory to the underlying platform.
	This metric is an overestimate, and not directly comparable to
	system CPU time measurements. Compare only with other /cpu/classes
	metrics.

	/cpu/classes/scavenge/total:cpu-seconds
	Estimated total CPU time spent performing tasks that return
	unused memory to the underlying platform.
	This metric is an overestimate, and not directly comparable to
	system CPU time measurements. Compare only with other /cpu/classes
	metrics. Sum of all metrics in /cpu/classes/scavenge.

	/cpu/classes/total:cpu-seconds
	Estimated total available CPU time for user Go code or the Go runtime, as
	defined by GOMAXPROCS. In other words, GOMAXPROCS integrated over the
	wall-clock duration this process has been executing for.
	This metric is an overestimate, and not directly comparable to
	system CPU time measurements. Compare only with other /cpu/classes
	metrics. Sum of all metrics in /cpu/classes.

	/cpu/classes/user:cpu-seconds
	Estimated total CPU time spent running user Go code. This may
	also include some small amount of time spent in the Go runtime.
	This metric is an overestimate, and not directly comparable to
	system CPU time measurements. Compare only with other /cpu/classes
	metrics.

	/gc/cycles/automatic:gc-cycles
	Count of completed GC cycles generated by the Go runtime.

	/gc/cycles/forced:gc-cycles
	Count of completed GC cycles forced by the application.

	/gc/cycles/total:gc-cycles
	Count of all completed GC cycles.

	/gc/heap/allocs-by-size:bytes
	Distribution of heap allocations by approximate size.
	Note that this does not include tiny objects as defined by /gc/heap/tiny/allocs:objects,
	only tiny blocks.

	/gc/heap/allocs:bytes
	Cumulative sum of memory allocated to the heap by the application.

	/gc/heap/allocs:objects
	Cumulative count of heap allocations triggered by the application.
	Note that this does not include tiny objects as defined by /gc/heap/tiny/allocs:objects,
	only tiny blocks.

	/gc/heap/frees-by-size:bytes
	Distribution of freed heap allocations by approximate size.
	Note that this does not include tiny objects as defined by /gc/heap/tiny/allocs:objects,
	only tiny blocks.

	/gc/heap/frees:bytes
	Cumulative sum of heap memory freed by the garbage collector.

	/gc/heap/frees:objects
	Cumulative count of heap allocations whose storage was freed by the garbage collector.
	Note that this does not include tiny objects as defined by /gc/heap/tiny/allocs:objects,
	only tiny blocks.

	/gc/heap/goal:bytes
	Heap size target for the end of the GC cycle.

	/gc/heap/objects:objects
	Number of objects, live or unswept, occupying heap memory.

	/gc/heap/tiny/allocs:objects
	Count of small allocations that are packed together into blocks.
	These allocations are counted separately from other allocations
	because each individual allocation is not tracked by the runtime,
	only their block. Each block is already accounted for in
	allocs-by-size and frees-by-size.

	/gc/limiter/last-enabled:gc-cycle
	GC cycle the last time the GC CPU limiter was enabled.
	This metric is useful for diagnosing the root cause of an out-of-memory
	error, because the limiter trades memory for CPU time when the GC's CPU
	time gets too high. This is most likely to occur with use of SetMemoryLimit.
	The first GC cycle is cycle 1, so a value of 0 indicates that it was never enabled.

	/gc/pauses:seconds
	Distribution individual GC-related stop-the-world pause latencies.

	/gc/stack/starting-size:bytes
	The stack size of new goroutines.

	/memory/classes/heap/free:bytes
	Memory that is completely free and eligible to be returned to
	the underlying system, but has not been. This metric is the
	runtime's estimate of free address space that is backed by
	physical memory.

	/memory/classes/heap/objects:bytes
	Memory occupied by live objects and dead objects that have
	not yet been marked free by the garbage collector.

	/memory/classes/heap/released:bytes
	Memory that is completely free and has been returned to
	the underlying system. This metric is the runtime's estimate of
	free address space that is still mapped into the process, but
	is not backed by physical memory.

	/memory/classes/heap/stacks:bytes
	Memory allocated from the heap that is reserved for stack
	space, whether or not it is currently in-use.

	/memory/classes/heap/unused:bytes
	Memory that is reserved for heap objects but is not currently
	used to hold heap objects.

	/memory/classes/metadata/mcache/free:bytes
	Memory that is reserved for runtime mcache structures, but
	not in-use.

	/memory/classes/metadata/mcache/inuse:bytes
	Memory that is occupied by runtime mcache structures that
	are currently being used.

	/memory/classes/metadata/mspan/free:bytes
	Memory that is reserved for runtime mspan structures, but
	not in-use.

	/memory/classes/metadata/mspan/inuse:bytes
	Memory that is occupied by runtime mspan structures that are
	currently being used.

	/memory/classes/metadata/other:bytes
	Memory that is reserved for or used to hold runtime
	metadata.

	/memory/classes/os-stacks:bytes
	Stack memory allocated by the underlying operating system.

	/memory/classes/other:bytes
	Memory used by execution trace buffers, structures for
	debugging the runtime, finalizer and profiler specials, and
	more.

	/memory/classes/profiling/buckets:bytes
	Memory that is used by the stack trace hash map used for
	profiling.

	/memory/classes/total:bytes
	All memory mapped by the Go runtime into the current process
	as read-write. Note that this does not include memory mapped
	by code called via cgo or via the syscall package.
	Sum of all metrics in /memory/classes.

	/sched/gomaxprocs:threads
	The current runtime.GOMAXPROCS setting, or the number of
	operating system threads that can execute user-level Go code
	simultaneously.

	/sched/goroutines:goroutines
	Count of live goroutines.

	/sched/latencies:seconds
	Distribution of the time goroutines have spent in the scheduler
	in a runnable state before actually running.

	/sync/mutex/wait/total:seconds
	Approximate cumulative time goroutines have spent blocked on a
	sync.Mutex or sync.RWMutex. This metric is useful for identifying
	global changes in lock contention. Collect a mutex or block
	profile using the runtime/pprof package for more detailed
	contention data.
	*/
	package metrics