golang 获取服务运行信息 服务监控

// A MemStats records statistics about the memory allocator. 记录内存分配器的信息
type MemStats struct {
    // General statistics.
    // Alloc is bytes of allocated heap objects.
    // 堆空间分配的字节数
    // This is the same as HeapAlloc (see below).
    Alloc uint64
    // TotalAlloc is cumulative bytes allocated for heap objects.
    //
    // TotalAlloc increases as heap objects are allocated, but
    // unlike Alloc and HeapAlloc, it does not decrease when
    // objects are freed. 从服务开始运行至今分配器为分配的堆空间总和
    TotalAlloc uint64
    // Sys is the total bytes of memory obtained from the OS.
    //
    // Sys is the sum of the XSys fields below. Sys measures the
    // virtual address space reserved by the Go runtime for the
    // heap, stacks, and other internal data structures. It's
    // likely that not all of the virtual address space is backed
    // by physical memory at any given moment, though in general
    // it all was at some point. 服务现在使用的内存
    Sys uint64
    // Lookups is the number of pointer lookups performed by the
    // runtime.
    //
    // This is primarily useful for debugging runtime internals. 被runtime监视的指针数
    Lookups uint64
    // Mallocs is the cumulative count of heap objects allocated. 服务malloc的次数
    // The number of live objects is Mallocs - Frees.
    Mallocs uint64
    // Frees is the cumulative count of heap objects freed. 服务回收的heap objects
    Frees uint64
    // Heap memory statistics.
    //
    // Interpreting the heap statistics requires some knowledge of
    // how Go organizes memory. Go divides the virtual address
    // space of the heap into "spans", which are contiguous
    // regions of memory 8K or larger. A span may be in one of
    // three states:
    //
    // An "idle" span contains no objects or other data. The
    // physical memory backing an idle span can be released back
    // to the OS (but the virtual address space never is), or it
    // can be converted into an "in use" or "stack" span.
    //
    // An "in use" span contains at least one heap object and may
    // have free space available to allocate more heap objects.
    //
    // A "stack" span is used for goroutine stacks. Stack spans
    // are not considered part of the heap. A span can change
    // between heap and stack memory; it is never used for both
    // simultaneously.
    // HeapAlloc is bytes of allocated heap objects.
    //
    // "Allocated" heap objects include all reachable objects, as
    // well as unreachable objects that the garbage collector has
    // not yet freed. Specifically, HeapAlloc increases as heap
    // objects are allocated and decreases as the heap is swept
    // and unreachable objects are freed. Sweeping occurs
    // incrementally between GC cycles, so these two processes
    // occur simultaneously, and as a result HeapAlloc tends to
    // change smoothly (in contrast with the sawtooth that is
    // typical of stop-the-world garbage collectors).
    //服务分配的堆内存
    HeapAlloc uint64
    // HeapSys is bytes of heap memory obtained from the OS.
    //
    // HeapSys measures the amount of virtual address space
    // reserved for the heap. This includes virtual address space
    // that has been reserved but not yet used, which consumes no
    // physical memory, but tends to be small, as well as virtual
    // address space for which the physical memory has been
    // returned to the OS after it became unused (see HeapReleased
    // for a measure of the latter).
    //
    // HeapSys estimates the largest size the heap has had.
    //系统分配的堆内存
    HeapSys uint64
    // HeapIdle is bytes in idle (unused) spans.
    //
    // Idle spans have no objects in them. These spans could be
    // (and may already have been) returned to the OS, or they can
    // be reused for heap allocations, or they can be reused as
    // stack memory.
    //
    // HeapIdle minus HeapReleased estimates the amount of memory
    // that could be returned to the OS, but is being retained by
    // the runtime so it can grow the heap without requesting more
    // memory from the OS. If this difference is significantly
    // larger than the heap size, it indicates there was a recent
    // transient spike in live heap size.
    //申请但是为分配的堆内存，（或者回收了的堆内存）
    HeapIdle uint64
    // HeapInuse is bytes in in-use spans.
    //
    // In-use spans have at least one object in them. These spans
    // can only be used for other objects of roughly the same
    // size.
    //
    // HeapInuse minus HeapAlloc esimates the amount of memory
    // that has been dedicated to particular size classes, but is
    // not currently being used. This is an upper bound on
    // fragmentation, but in general this memory can be reused
    // efficiently.
    //正在使用的堆内存
    HeapInuse uint64
    // HeapReleased is bytes of physical memory returned to the OS.
    //
    // This counts heap memory from idle spans that was returned
    // to the OS and has not yet been reacquired for the heap.
    //返回给OS的堆内存，类似C/C++中的free。
    HeapReleased uint64
    // HeapObjects is the number of allocated heap objects.
    //
    // Like HeapAlloc, this increases as objects are allocated and
    // decreases as the heap is swept and unreachable objects are
    // freed.
    //堆内存块申请的量
    HeapObjects uint64
    // Stack memory statistics.
    //
    // Stacks are not considered part of the heap, but the runtime
    // can reuse a span of heap memory for stack memory, and
    // vice-versa.
    // StackInuse is bytes in stack spans.
    //
    // In-use stack spans have at least one stack in them. These
    // spans can only be used for other stacks of the same size.
    //
    // There is no StackIdle because unused stack spans are
    // returned to the heap (and hence counted toward HeapIdle).
    //正在使用的栈
    StackInuse uint64
    // StackSys is bytes of stack memory obtained from the OS.
    //
    // StackSys is StackInuse, plus any memory obtained directly
    // from the OS for OS thread stacks (which should be minimal).
    //系统分配的作为运行栈的内存
    StackSys uint64
    // Off-heap memory statistics.
    //
    // The following statistics measure runtime-internal
    // structures that are not allocated from heap memory (usually
    // because they are part of implementing the heap). Unlike
    // heap or stack memory, any memory allocated to these
    // structures is dedicated to these structures.
    //
    // These are primarily useful for debugging runtime memory
    // overheads.
    // MSpanInuse is bytes of allocated mspan structures. 用于测试用的结构体使用的字节数
    MSpanInuse uint64
    // MSpanSys is bytes of memory obtained from the OS for mspan
    // structures. 系统为测试用的结构体分配的字节数
    MSpanSys uint64
    // MCacheInuse is bytes of allocated mcache structures. mcache结构体申请的字节数
    MCacheInuse uint64
    // MCacheSys is bytes of memory obtained from the OS for
    // mcache structures. 操作系统申请的堆空间用于mcache的量
    MCacheSys uint64
    // BuckHashSys is bytes of memory in profiling bucket hash tables.用于剖析桶散列表的堆空间
    BuckHashSys uint64
    // GCSys is bytes of memory in garbage collection metadata. 垃圾回收标记元信息使用的内存
    GCSys uint64
    // OtherSys is bytes of memory in miscellaneous off-heap
    // runtime allocations. golang系统架构占用的额外空间
    OtherSys uint64
    // Garbage collector statistics.
    // 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. 垃圾回收器检视的内存大小
    NextGC uint64
    // LastGC is the time the last garbage collection finished, as
    // nanoseconds since 1970 (the UNIX epoch).
    // 垃圾回收器最后一次执行时间。
    LastGC uint64
    // PauseTotalNs is the cumulative nanoseconds in GC
    // stop-the-world pauses since the program started.
    //
    // During a stop-the-world pause, all goroutines are paused
    // and only the garbage collector can run.
    // 垃圾回收或者其他信息收集导致服务暂停的次数。
    PauseTotalNs uint64
    // PauseNs is a circular buffer of recent GC stop-the-world
    // pause times in nanoseconds.
    //
    // The most recent pause is at PauseNs[(NumGC+255)%256]. In
    // general, PauseNs[N%256] records the time paused in the most
    // recent N%256th GC cycle. There may be multiple pauses per
    // GC cycle; this is the sum of all pauses during a cycle. 一个循环队列，记录最近垃圾回收系统中断的时间
    PauseNs [256]uint64
    // PauseEnd is a circular buffer of recent GC pause end times,
    // as nanoseconds since 1970 (the UNIX epoch).
    //
    // This buffer is filled the same way as PauseNs. There may be
    // multiple pauses per GC cycle; this records the end of the
    // last pause in a cycle. 一个循环队列，记录最近垃圾回收系统中断的时间开始点。
    PauseEnd [256]uint64
    // NumGC is the number of completed GC cycles.
    //垃圾回收的内存大小
    NumGC uint32
    // NumForcedGC is the number of GC cycles that were forced by
    // the application calling the GC function.
    //服务调用runtime.GC()强制使用垃圾回收的次数。
    NumForcedGC uint32
    // GCCPUFraction is the fraction of this program's available
    // CPU time used by the GC since the program started.
    //
    // GCCPUFraction is expressed as a number between 0 and 1,
    // where 0 means GC has consumed none of this program's CPU. A
    // program's available CPU time is defined as the integral of
    // GOMAXPROCS since the program started. That is, if
    // GOMAXPROCS is 2 and a program has been running for 10
    // seconds, its "available CPU" is 20 seconds. GCCPUFraction
    // does not include CPU time used for write barrier activity.
    //
    // This is the same as the fraction of CPU reported by
    // GODEBUG=gctrace=1.
    //垃圾回收占用服务CPU工作的时间总和。如果有100个goroutine，垃圾回收的时间为1S,那么久占用了100S
    GCCPUFraction float64
    // EnableGC indicates that GC is enabled. It is always true,
    // even if GOGC=off.
    //是否启用GC
    EnableGC bool
    // DebugGC is currently unused.
    DebugGC bool
    // BySize reports per-size class allocation statistics.
    //
    // BySize[N] gives statistics for allocations of size S where
    // BySize[N-1].Size < S ≤ BySize[N].Size.
    //
    // This does not report allocations larger than BySize[60].Size.
    //内存分配器使用情况
    BySize [61]struct {
        // Size is the maximum byte size of an object in this
        // size class.
        Size uint32
        // Mallocs is the cumulative count of heap objects
        // allocated in this size class. The cumulative bytes
        // of allocation is Size*Mallocs. The number of live
        // objects in this size class is Mallocs - Frees.
        Mallocs uint64
        // Frees is the cumulative count of heap objects freed
        // in this size class.
        Frees uint64
    }
}