[dev.link] all: merge branch 'master' into dev.linkdev.link

Clean merge.

Change-Id: Ia7b2808bc649790198d34c226a61d9e569084dc5

1 files changed, 130 insertions, 0 deletions

diff --git a/src/runtime/metrics/doc.go b/src/runtime/metrics/doc.go
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+// 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, such as how to display it (e.g. gauge vs. counter) and how difficult
+or disruptive it is to obtain it (e.g. do you need to stop the world?).
+
+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
+encouranged 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.
+
+Supported metrics
+
+	/gc/cycles/automatic:gc-cycles
+		Count of completed GC cycles generated by the Go runtime.
+
+	/gc/cycles/forced:gc-cycles
+		Count of completed forced GC cycles.
+
+	/gc/cycles/total:gc-cycles
+		Count of all completed GC cycles.
+
+	/gc/heap/allocs-by-size:objects
+		Distribution of all objects allocated by approximate size.
+
+	/gc/heap/frees-by-size:objects
+		Distribution of all objects freed by approximate size.
+
+	/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/pauses:seconds
+		Distribution individual GC-related stop-the-world pause latencies.
+
+	/memory/classes/heap/free:bytes
+		Memory that is available for allocation, and may be returned
+		to the underlying system.
+
+	/memory/classes/heap/objects:bytes
+		Memory occupied by live objects and dead objects that have
+		not yet been collected.
+
+	/memory/classes/heap/released:bytes
+		Memory that has been returned to the underlying system.
+
+	/memory/classes/heap/stacks:bytes
+		Memory allocated from the heap that is occupied by stacks.
+
+	/memory/classes/heap/unused:bytes
+		Memory that is unavailable for allocation, but cannot be
+		returned to the underlying system.
+
+	/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/goroutines:goroutines
+		Count of live goroutines.
+*/
+package metrics