英文:
runtime.duffcopy is called a lot
问题
当我对我的应用程序进行分析并运行top命令时，我看到以下输出：
显示前10个节点中的31个节点（cum >= 0.12s）
flat flat% sum% cum cum%
13.93s 63.00% 63.00% 13.93s 63.00% runtime.duffcopy
我很难知道它是何时以及为什么被调用的，是否有什么方法可以改进它？您是否需要查看调用这些函数的函数，或者是否有任何一般性的经验法则我应该考虑？
我已经阅读到命名返回值可以改进这个问题，但这是一个相当大的函数，测试了很多条件（返回true或false），所以不知道是否实施这个方法是一个好主意。
谢谢。
英文:
When profiling my app, and run top, I see
Showing top 10 nodes out of 31 (cum >= 0.12s)
flat flat% sum% cum cum%
13.93s 63.00% 63.00% 13.93s 63.00% runtime.duffcopy
I am struggling to know when and why it is called and if there is something I can do to improve this? Would you need to see the function from where these calls are made from or is there any general rule-of-thumb that I should think about?
I have read that named return values can improve this, but its quite a big function testing a lot of conditions (returning true or false), so don't know if its a good idea to implement that.
Thanks
答案1
得分: 12
我刚刚解决了这个问题。我查看了汇编输出，发现我有一个循环：
for _, v := range c.Items
一个Item对象相对较大，所以我用下面的循环替换了上面的循环：
for index := 0; index < len(c.Items); index++
并且直接访问对象，如c.Items[index]。现在顶部显示：
350ms 4.85% 60.47% 350ms 4.85% runtime.duffcopy
整体执行时间从12秒减少到4秒。非常不错 
英文:
Think I just solved it. I had a look at the assembly output and saw that I had a
for _, v := range c.Items
an Item is a relatively big object, so I replaced above loop with
for index := 0; index < len(c.Items); index++
and used direct access of the objects like c.Items[index]. Top now shows:
350ms 4.85% 60.47% 350ms 4.85% runtime.duffcopy
The overall execution time was cut from 12s to 4s. Quite nice
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