go

Why is atomic.StoreUint32 preferred over a normal assignment in sync.Once?

由 喜夏-厌秋 提交于 2021-02-07 04:15:26
问题 While reading the source codes of Go, I have a question about the code in src/sync/once.go: func (o *Once) Do(f func()) { // Note: Here is an incorrect implementation of Do: // // if atomic.CompareAndSwapUint32(&o.done, 0, 1) { // f() // } // // Do guarantees that when it returns, f has finished. // This implementation would not implement that guarantee: // given two simultaneous calls, the winner of the cas would // call f, and the second would return immediately, without // waiting for the

Why is atomic.StoreUint32 preferred over a normal assignment in sync.Once?

由 你说的曾经没有我的故事 提交于 2021-02-07 04:05:36
问题 While reading the source codes of Go, I have a question about the code in src/sync/once.go: func (o *Once) Do(f func()) { // Note: Here is an incorrect implementation of Do: // // if atomic.CompareAndSwapUint32(&o.done, 0, 1) { // f() // } // // Do guarantees that when it returns, f has finished. // This implementation would not implement that guarantee: // given two simultaneous calls, the winner of the cas would // call f, and the second would return immediately, without // waiting for the

Go 1.13 RSS keeps on increasing, suspected scavenging issue

由 元气小坏坏 提交于 2021-02-07 03:41:13
问题 We are experiencing RSS that keeps on increasing in one of our Go service. We are suspecting it's due to scavenger not returning memory to OS properly (or OS not taking back the memory due to use of MADV_FREE). Checked via pprof, no memory leak detected. We tried some experiment with the following simple Go program: Go version: go1.13.4 linux/amd64 (tried with go1.13.1 too) package main import ( "fmt" "time" ) func allocate(s int) { a := make([]byte, s * 1024 * 1024) for i := 0;i < len(a); i

How to access fields of a JSON in GO

由 我与影子孤独终老i 提交于 2021-02-07 03:08:17
问题 Hi everyone I'm trying to see what the proper way of accessing fields of a json object from a http.get request in go. I first do an http.get call get the JSON and then print it (which works) but is there a way to access just a field? for example: response, err:= http.Get("URL") //Error checking is done between contents, err:=ioutil.Readall(response.Body) //Now at this point I have a json that looks like {"id": "someID", "name": "someName", "test": [{"Name":"Test1", "Result": "Success"}, {

详解Go中内存分配源码实现

由 匆匆过客 提交于 2021-02-07 02:44:30
转载请声明出处哦~，本篇文章发布于luozhiyun的博客： https://www.luozhiyun.com 本文使用的go的源码15.7 介绍 Go 语言的内存分配器就借鉴了 TCMalloc 的设计实现高速的内存分配，它的核心理念是使用多级缓存将对象根据大小分类，并按照类别实施不同的分配策略。TCMalloc 相关的信息可以看这里： http://goog-perftools.sourceforge.net/doc/tcmalloc.html。 即如果要分配的对象是个小对象（<= 32k），在每个线程中都会有一个无锁的小对象缓存，可以直接高效的无锁的方式进行分配； 如下：对象被分到不同的内存大小组中的链表中。 如果是个大对象（>32k），那么页堆进行分配。如下： 虽然go内存分配器最初是基于tcmalloc的，但是现在已经有了很大的不同。所以上面的一些结构会有些许变化，下面再慢慢絮叨。 因为内存分配的源码比较复杂，为了方便大家调试，所以在进行源码分析之前，先看看是如何断点汇编来进行调试的。 断点调试汇编 目前Go语言支持GDB、LLDB和Delve几种调试器。只有Delve是专门为Go语言设计开发的调试工具。而且Delve本身也是采用Go语言开发，对Windows平台也提供了一样的支持。本节我们基于Delve简单解释如何调试Go汇编程序。项目地址： https:/

关于JS

由 柔情痞子 提交于 2021-02-07 00:02:36
主流浏览器的内核 IE：trident Chrome：webkit/blink firefox：Gecko Opera：presto Safari：webkit 引入JS的方式 页面内嵌标签（可在head内或body内） 外部引入（常用方法） JS基本语法 变量： 变量声明：声明，赋值分解。单一var。 （var a=100） 命名规则：变量名必须以英文字母，*，$开头* 变量名可以包括英文字母，，$，数字 不可以用系统的关键字，保留字作为变量名 值类型（数据类型）： 不可改变的原始值（栈数据）：Number，Boolean，String，undefined，null 栈内存和栈内存之间赋值是拷贝（互不影响） 引用值（堆数据）：array，Object，function，..data，RegExp typeof()可查看数据类型（返回number，string，boolean，object，undefined，function） 类型转换：显式类型转换：Number(mix) 转换不了的就显示为NaN parseInt(string,radix) string以radix进制为基底转换为10进制 parseFloat(string) num.toString(radix) num转为radix进制 String(mix) Boolean() 隐式类型转换：isNaN()

How to log Stackdriver log messages correlated by trace id using stdout Go 1.11

由 邮差的信 提交于 2021-02-06 11:57:10
问题 I'm using Google App Engine Standard Environment with the Go 1.11 runtime. The documentation for Go 1.11 says "Write your application logs using stdout for output and stderr for errors". The migration from Go 1.9 guide also suggests not calling the Google Cloud Logging library directly but instead logging via stdout. https://cloud.google.com/appengine/docs/standard/go111/writing-application-logs With this in mind, I've written a small HTTP Service (code below) to experiment logging to

How to log Stackdriver log messages correlated by trace id using stdout Go 1.11

由 ≡放荡痞女 提交于 2021-02-06 11:56:08
问题 I'm using Google App Engine Standard Environment with the Go 1.11 runtime. The documentation for Go 1.11 says "Write your application logs using stdout for output and stderr for errors". The migration from Go 1.9 guide also suggests not calling the Google Cloud Logging library directly but instead logging via stdout. https://cloud.google.com/appengine/docs/standard/go111/writing-application-logs With this in mind, I've written a small HTTP Service (code below) to experiment logging to

From []byte to char*

由 一世执手 提交于 2021-02-06 10:16:50
问题 I want to wrap a C function that takes a char* pointing to (the first element of) a non-empty buffer of bytes. I'm trying to wrap that in a Go function using CGo so that I can pass it a []byte , but I don't know how to do the conversion. A simplified version of the C function's signature is void foo(char const *buf, size_t n); I tried passing a pointer to the first byte in the slice with C.foo(&b[0], C.size_t(n)) That doesn't compile, though: cannot use &b[0] (type *byte) as type *_Ctype_char

what is the golang equivalent of a Java synchronized() block?

由 半腔热情 提交于 2021-02-06 09:57:08
问题 Java provides a very convenient idiom for synchronizing critical portions of code: synchronized(someObject) { // do something really important all by myself with nobody bothering me } Or public synchronized void doSomething() { // ... } What is the go equivalent? (A quick search reveals: golang.org/pkg/sync/ - which seems (maybe I'm wrong) a bit too low level for general use.) (Example of why I care about this: I need to send a message to multiple listeners via channels. Channels provide a
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