Thank you! I change the code as your suggestion, it reduce 10% cpu usage.
在 2020年5月21日星期四 UTC+8下午1:04:34，Ian Lance Taylor写道：
>
> On Wed, May 20, 2020 at 9:26 PM <qing...@gmail.com <javascript:>> 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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