diff options
Diffstat (limited to 'src/runtime/metrics/doc.go')
| -rw-r--r-- | src/runtime/metrics/doc.go | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/src/runtime/metrics/doc.go b/src/runtime/metrics/doc.go new file mode 100644 index 0000000000..e340f3d0dd --- /dev/null +++ b/src/runtime/metrics/doc.go @@ -0,0 +1,130 @@ +// 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 |