On Wed, May 20, 2020 at 9:26 PM <qingyu...@gmail.com> wrote:
>
> Hi all:
> I write a simpile HTTP proxy，and find the most alloctions appear in
> io.copyBuffer
>
>>> (pprof) list io.copyBuffer
>>>
>>> Total: 2.80TB
>>>
>>> ROUTINE ======================== io.copyBuffer in /usr/local/go/src/io/io.go
>>>
>>> 1.03TB 2.47TB (flat, cum) 88.16% of Total
>>>
>>> . . 383: if wt, ok := src.(WriterTo); ok {
>>>
>>> . . 384: return wt.WriteTo(dst)
>>>
>>> . . 385: }
>>>
>>> . . 386: // Similarly, if the writer has a ReadFrom
>>> method, use it to do the copy.
>>>
>>> . . 387: if rt, ok := dst.(ReaderFrom); ok {
>>>
>>> . 3.02GB 388: return rt.ReadFrom(src)
>>>
>>> . . 389: }
>>>
>>> . . 390: if buf == nil {
>>>
>>> . . 391: size := 32 * 1024
>>>
>>> . . 392: if l, ok := src.(*LimitedReader);
>>> ok && int64(size) > l.N {
>>>
>>> . . 393: if l.N < 1 {
>>>
>>> . . 394: size = 1
>>>
>>> . . 395: } else {
>>>
>>> . . 396: size = int(l.N)
>>>
>>> . . 397: }
>>>
>>> . . 398: }
>>>
>>> 1.03TB 1.03TB 399: buf = make([]byte, size)
>>>
>>> . . 400: }
>>>
>>> . . 401: for {
>>>
>>> . 1.43TB 402: nr, er := src.Read(buf)
>>>
>>> . . 403: if nr > 0 {
>>>
>>> . 569.57MB 404: nw, ew :=
>>> dst.Write(buf[0:nr])
>>>
>>> . . 405: if nw > 0 {
>>>
>>> . . 406: written += int64(nw)
>>>
>>> . . 407: }
>>>
>>> . . 408: if ew != nil {
>>>
>>> . . 409: err = ew
>
>
> and this the stacktrace
>>
>> 0: 0 [2057907: 67433496576] @ 0x470169 0x6e508a 0x6e5042 0x6e4ca7 0x6cf82e
>> 0x77bfe9 0x45f7a1
>>
>> # 0x470168 io.copyBuffer+0x2a8
>> /usr/local/go/src/io/io.go:399
>>
>> # 0x6e5089 io.Copy+0x69
>> /usr/local/go/src/io/io.go:364
>>
>> # 0x6e5041 net/http.(*transferWriter).doBodyCopy+0x21
>> /usr/local/go/src/net/http/transfer.go:400
>>
>> # 0x6e4ca6 net/http.(*transferWriter).writeBody+0x426
>> /usr/local/go/src/net/http/transfer.go:348
>>
>> # 0x6cf82d net/http.(*Response).Write+0x42d
>> /usr/local/go/src/net/http/response.go:328
>>
>> # 0x77bfe8 main.handler+0x318
>> /root/ctrip/shendun/main.go:74
The data being copied is presumably coming from the Body field of your
*http.Response. If you set the Body field to a type that implements
the WriteTo method, and set the ContentLength field to the length of
the data, then you can do the write however you like.
Ian
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