runtime.adjustdefers在pprof输出中意味着什么？

我们正在运行一个Go程序，该程序大部分时间用于GC。我们使用了内存配置文件，并执行了“go tool pprof -alloc_objects”。然后，我在打印机控制台上做了一个'top5'，以下是它显示的内容：runtime.adjustdefers在pprof输出中意味着什么？

我的问题是，runtime.adjustdefers是什么意思？

(pprof) top5 
4576708929 of 7330217181 total (62.44%) 
Dropped 765 nodes (cum <= 36651085) 
Showing top 5 nodes out of 88 (cum >= 970919101) 
     flat flat% sum%  cum cum% 
2035058528 27.76% 27.76% 2035058528 27.76% runtime.adjustdefers 
996366409 13.59% 41.36% 1284278077 17.52% github.com/pelletier/go-buffruneio.init 
627682563 8.56% 49.92% 916069310 12.50% github.com/prometheus/common/expfmt.MetricFamilyToText 
509166106 6.95% 56.86% 509166106 6.95% encoding/csv.(*Reader).ReadAll 
408435323 5.57% 62.44% 970919101 13.25% golang.org/x/net/html.init

来源

2017-04-20 Joe Lin

The Go Programming Language Specification

Defer statements

A “推迟” 语句调用它的执行被推迟到此刻周围的函数返回的功能，要么是因为周围函数执行return语句，其功能体达到了的末尾，或者是因为相应的门厅是恐慌。

go/src/runtime/stack.go：

func adjustdefers(gp *g, adjinfo *adjustinfo) { 
    // Adjust defer argument blocks the same way we adjust active stack frames. 
    tracebackdefers(gp, adjustframe, noescape(unsafe.Pointer(adjinfo))) 

    // Adjust pointers in the Defer structs. 
    // Defer structs themselves are never on the stack. 
    for d := gp._defer; d != nil; d = d.link { 
     adjustpointer(adjinfo, unsafe.Pointer(&d.fn)) 
     adjustpointer(adjinfo, unsafe.Pointer(&d.sp)) 
     adjustpointer(adjinfo, unsafe.Pointer(&d._panic)) 
    } 
}

go/src/runtime/stack.go：

// Copies gp's stack to a new stack of a different size. 
// Caller must have changed gp status to Gcopystack. 
// 
// If sync is true, this is a self-triggered stack growth and, in 
// particular, no other G may be writing to gp's stack (e.g., via a 
// channel operation). If sync is false, copystack protects against 
// concurrent channel operations. 
func copystack(gp *g, newsize uintptr, sync bool) { 
    // . . . 
    // allocate new stack 
    new := stackalloc(uint32(newsize)) 
    if stackPoisonCopy != 0 { 
     fillstack(new, 0xfd) 
    } 
    // . . . 
    // Compute adjustment. 
    var adjinfo adjustinfo 
    adjinfo.old = old 
    adjinfo.delta = new.hi - old.hi 
    // . . . 
    // Adjust remaining structures that have pointers into stacks. 
    // We have to do most of these before we traceback the new 
    // stack because gentraceback uses them. 
    adjustctxt(gp, &adjinfo) 
    adjustdefers(gp, &adjinfo) 
    adjustpanics(gp, &adjinfo) 
    if adjinfo.sghi != 0 { 
     adjinfo.sghi += adjinfo.delta 
    } 
    // . . . 
}

从我的代码的读取，当一个够程小号调整大小adjustdefers对延迟函数进行指针调整。

你说你正在运行一个Go程序，它大部分时间都在做GC。第二高的包是github.com/pelletier/go-buffruneio。代码看起来效率低下。这是阅读符文的简单基准。

package main 

import (
    "bufio" 
    "bytes" 
    "io" 
    "testing" 

    "github.com/pelletier/go-buffruneio" 
) 

var buf = make([]byte, 64*1024) 

func BenchmarkBuffruneio(b *testing.B) { 
    b.ReportAllocs() 
    for i := 0; i < b.N; i++ { 
     r := buffruneio.NewReader(bytes.NewBuffer(buf[:cap(buf)])) 
     for { 
      rune, _, err := r.ReadRune() 
      if err == io.EOF || rune == buffruneio.EOF { 
       break 
      } 
     } 
    } 
} 

func BenchmarkBufio(b *testing.B) { 
    b.ReportAllocs() 
    for i := 0; i < b.N; i++ { 
     r := bufio.NewReader(bytes.NewBuffer(buf[:cap(buf)])) 
     for { 
      _, _, err := r.ReadRune() 
      if err == io.EOF { 
       break 
      } 
     } 
    } 
}

输出：

$ go test -v -bench=. 
goos: linux 
goarch: amd64 
pkg: so/runes 
BenchmarkBuffruneio-2  200 9395482 ns/op 4198721 B/op 131078 allocs/op 
BenchmarkBufio-2   3000  333731 ns/op  4208 B/op   2 allocs/op 
PASS 
ok  so/runes 3.878s 
$

来源

2017-04-20 12:29:02 peterSO

runtime.adjustdefers在pprof输出中意味着什么？

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