github.com/lzhfromustc/gofuzz@v0.0.0-20211116160056-151b3108bbd1/runtime/metrics/doc.go (about) 1 // Copyright 2020 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 /* 6 Package metrics provides a stable interface to access implementation-defined 7 metrics exported by the Go runtime. This package is similar to existing functions 8 like runtime.ReadMemStats and debug.ReadGCStats, but significantly more general. 9 10 The set of metrics defined by this package may evolve as the runtime itself 11 evolves, and also enables variation across Go implementations, whose relevant 12 metric sets may not intersect. 13 14 Interface 15 16 Metrics are designated by a string key, rather than, for example, a field name in 17 a struct. The full list of supported metrics is always available in the slice of 18 Descriptions returned by All. Each Description also includes useful information 19 about the metric. 20 21 Thus, users of this API are encouraged to sample supported metrics defined by the 22 slice returned by All to remain compatible across Go versions. Of course, situations 23 arise where reading specific metrics is critical. For these cases, users are 24 encouraged to use build tags, and although metrics may be deprecated and removed, 25 users should consider this to be an exceptional and rare event, coinciding with a 26 very large change in a particular Go implementation. 27 28 Each metric key also has a "kind" that describes the format of the metric's value. 29 In the interest of not breaking users of this package, the "kind" for a given metric 30 is guaranteed not to change. If it must change, then a new metric will be introduced 31 with a new key and a new "kind." 32 33 Metric key format 34 35 As mentioned earlier, metric keys are strings. Their format is simple and well-defined, 36 designed to be both human and machine readable. It is split into two components, 37 separated by a colon: a rooted path and a unit. The choice to include the unit in 38 the key is motivated by compatibility: if a metric's unit changes, its semantics likely 39 did also, and a new key should be introduced. 40 41 For more details on the precise definition of the metric key's path and unit formats, see 42 the documentation of the Name field of the Description struct. 43 44 A note about floats 45 46 This package supports metrics whose values have a floating-point representation. In 47 order to improve ease-of-use, this package promises to never produce the following 48 classes of floating-point values: NaN, infinity. 49 50 Supported metrics 51 52 Below is the full list of supported metrics, ordered lexicographically. 53 54 /gc/cycles/automatic:gc-cycles 55 Count of completed GC cycles generated by the Go runtime. 56 57 /gc/cycles/forced:gc-cycles 58 Count of completed GC cycles forced by the application. 59 60 /gc/cycles/total:gc-cycles 61 Count of all completed GC cycles. 62 63 /gc/heap/allocs-by-size:bytes 64 Distribution of all objects allocated by approximate size. 65 66 /gc/heap/frees-by-size:bytes 67 Distribution of all objects freed by approximate size. 68 69 /gc/heap/goal:bytes 70 Heap size target for the end of the GC cycle. 71 72 /gc/heap/objects:objects 73 Number of objects, live or unswept, occupying heap memory. 74 75 /gc/pauses:seconds 76 Distribution individual GC-related stop-the-world pause latencies. 77 78 /memory/classes/heap/free:bytes 79 Memory that is completely free and eligible to be returned to 80 the underlying system, but has not been. This metric is the 81 runtime's estimate of free address space that is backed by 82 physical memory. 83 84 /memory/classes/heap/objects:bytes 85 Memory occupied by live objects and dead objects that have 86 not yet been marked free by the garbage collector. 87 88 /memory/classes/heap/released:bytes 89 Memory that is completely free and has been returned to 90 the underlying system. This metric is the runtime's estimate of 91 free address space that is still mapped into the process, but 92 is not backed by physical memory. 93 94 /memory/classes/heap/stacks:bytes 95 Memory allocated from the heap that is reserved for stack 96 space, whether or not it is currently in-use. 97 98 /memory/classes/heap/unused:bytes 99 Memory that is reserved for heap objects but is not currently 100 used to hold heap objects. 101 102 /memory/classes/metadata/mcache/free:bytes 103 Memory that is reserved for runtime mcache structures, but 104 not in-use. 105 106 /memory/classes/metadata/mcache/inuse:bytes 107 Memory that is occupied by runtime mcache structures that 108 are currently being used. 109 110 /memory/classes/metadata/mspan/free:bytes 111 Memory that is reserved for runtime mspan structures, but 112 not in-use. 113 114 /memory/classes/metadata/mspan/inuse:bytes 115 Memory that is occupied by runtime mspan structures that are 116 currently being used. 117 118 /memory/classes/metadata/other:bytes 119 Memory that is reserved for or used to hold runtime 120 metadata. 121 122 /memory/classes/os-stacks:bytes 123 Stack memory allocated by the underlying operating system. 124 125 /memory/classes/other:bytes 126 Memory used by execution trace buffers, structures for 127 debugging the runtime, finalizer and profiler specials, and 128 more. 129 130 /memory/classes/profiling/buckets:bytes 131 Memory that is used by the stack trace hash map used for 132 profiling. 133 134 /memory/classes/total:bytes 135 All memory mapped by the Go runtime into the current process 136 as read-write. Note that this does not include memory mapped 137 by code called via cgo or via the syscall package. 138 Sum of all metrics in /memory/classes. 139 140 /sched/goroutines:goroutines 141 Count of live goroutines. 142 */ 143 package metrics