mirror of
https://github.com/golang/go
synced 2024-10-05 12:31:23 -06:00
9fb96991e6
Fixes #4434. This proposal replaces the previous CL 6855110. Due to issue 599, 64-bit atomic operations should probably be avoided, so use a sync.Mutex instead. Benchmark comparisons against 025b9d070a85 on linux/386: CL 6855110: benchmark old ns/op new ns/op delta BenchmarkTCPOneShot 710024 727409 +2.45% BenchmarkTCPOneShotTimeout 758178 768620 +1.38% BenchmarkTCPPersistent 223464 228058 +2.06% BenchmarkTCPPersistentTimeout 234494 242600 +3.46% This proposal: benchmark old ns/op new ns/op delta BenchmarkTCPOneShot 710024 718492 +1.19% BenchmarkTCPOneShotTimeout 758178 748783 -1.24% BenchmarkTCPPersistent 223464 227628 +1.86% BenchmarkTCPPersistentTimeout 234494 238321 +1.63% R=rsc, dvyukov, mikioh.mikioh, alex.brainman, bradfitz CC=golang-dev, remyoudompheng https://golang.org/cl/6866050
106 lines
2.4 KiB
Go
106 lines
2.4 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package net
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import (
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"io"
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"os"
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"syscall"
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)
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// maxSendfileSize is the largest chunk size we ask the kernel to copy
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// at a time.
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const maxSendfileSize int = 4 << 20
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// sendFile copies the contents of r to c using the sendfile
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// system call to minimize copies.
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//
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// if handled == true, sendFile returns the number of bytes copied and any
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// non-EOF error.
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//
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// if handled == false, sendFile performed no work.
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func sendFile(c *netFD, r io.Reader) (written int64, err error, handled bool) {
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// FreeBSD uses 0 as the "until EOF" value. If you pass in more bytes than the
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// file contains, it will loop back to the beginning ad nauseum until it's sent
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// exactly the number of bytes told to. As such, we need to know exactly how many
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// bytes to send.
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var remain int64 = 0
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lr, ok := r.(*io.LimitedReader)
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if ok {
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remain, r = lr.N, lr.R
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if remain <= 0 {
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return 0, nil, true
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}
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}
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f, ok := r.(*os.File)
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if !ok {
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return 0, nil, false
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}
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if remain == 0 {
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fi, err := f.Stat()
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if err != nil {
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return 0, err, false
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}
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remain = fi.Size()
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}
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// The other quirk with FreeBSD's sendfile implementation is that it doesn't
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// use the current position of the file -- if you pass it offset 0, it starts
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// from offset 0. There's no way to tell it "start from current position", so
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// we have to manage that explicitly.
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pos, err := f.Seek(0, os.SEEK_CUR)
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if err != nil {
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return 0, err, false
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}
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c.wio.Lock()
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defer c.wio.Unlock()
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if err := c.incref(false); err != nil {
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return 0, err, true
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}
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defer c.decref()
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dst := c.sysfd
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src := int(f.Fd())
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for remain > 0 {
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n := maxSendfileSize
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if int64(n) > remain {
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n = int(remain)
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}
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pos1 := pos
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n, err1 := syscall.Sendfile(dst, src, &pos1, n)
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if n > 0 {
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pos += int64(n)
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written += int64(n)
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remain -= int64(n)
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}
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if n == 0 && err1 == nil {
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break
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}
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if err1 == syscall.EAGAIN {
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if err1 = c.pollServer.WaitWrite(c); err1 == nil {
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continue
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}
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}
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if err1 == syscall.EINTR {
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continue
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}
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if err1 != nil {
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// This includes syscall.ENOSYS (no kernel
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// support) and syscall.EINVAL (fd types which
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// don't implement sendfile together)
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err = &OpError{"sendfile", c.net, c.raddr, err1}
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break
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}
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}
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if lr != nil {
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lr.N = remain
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}
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return written, err, written > 0
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}
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