blocks|key|643393|text|您没有提到特定的操作系统，但大多数情况下，数据在堆栈中传输，直到到达IP为止，此时数据几乎被发送回来。这是一个大规模的过度简化，但意味着整个进程通常是CPU绑定，因此它的性能直接联系到CPU速度和堆栈效率。实际上，现代CPU和开放源码软件应该能够比40+40Gbps更快地“反弹”回送流量--这是我今天能买到的最快的网卡。希望这能有所帮助。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|entityMap^0^^$0|@$1|2|3|4|5|6|7|C|8|@]|9|@]|A|$]]]|B|$]]

You don't mention a particular OS but for most all that happens is that the data travels down the stack until it gets to IP at which point it's pretty much sent back. That's a massive oversimplification but means that the entire process is usually CPU bound so its performance is therefore directly linked to CPU speed plus stack efficiency. In practical terms modern CPUs and OSs should be able to 'bounce' loopback traffic considerably faster than 40Gbps - which is the fastest NIC I think I'm capable of buying today. Hope this helps.

blocks|key|643381|text|所有127.xx.xx.xx流量都不会到达物理网络，而是由内核中的循环回适配器处理。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|entityMap^0^^$0|@$1|2|3|4|5|6|7|C|8|@]|9|@]|A|$]]]|B|$]]

All 127.xx.xx.xx traffic never hits the physical network, it gets processed by a loop back adapter in the kernel.

blocks|key|5890080|text|您可能对微软在Windows+8和Windows+2012中添加的“回环快速路径”功能感兴趣。请参见：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5890081|http://blogs.technet.com/b/wincat/archive/2012/12/05/fast-tcp-loopback-performance-and-low-latency-with-windows-server-2012-tcp-loopback-fast-path.aspx|offset|length|5890082|它还说明了环回在优化和不优化的情况下所采取的路径。|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|47|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|G|5|6|7|S|8|@]|9|@]|A|$]]]|H|$I|$5|J|K|L|A|$M|C]]]]

You may be interested in the "Loopback Fast Path" feature Microsoft added in Windows 8 and Windows Server 2012. See: 

<a href="http://blogs.technet.com/b/wincat/archive/2012/12/05/fast-tcp-loopback-performance-and-low-latency-with-windows-server-2012-tcp-loopback-fast-path.aspx" rel="nofollow noreferrer">http://blogs.technet.com/b/wincat/archive/2012/12/05/fast-tcp-loopback-performance-and-low-latency-with-windows-server-2012-tcp-loopback-fast-path.aspx</a>

It also provides an illustration of the path taken by the loopback with and without the optimization.

blocks|key|5890004|text|任何其他本地ip都不会比127.0.0.1更快。本地ip速度快，因为它不使用物理设备和2层(它从来没有击中你的网卡)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5890005|iperf+-c+109.191.109.xxx+1111+-t+5
iperf:+ignoring+extra+argument+--+1111
------------------------------------------------------------
Client+connecting+to+109.191.109.241,+TCP+port+5001
TCP+window+size:+49.7+KByte+(default)
------------------------------------------------------------
[++3]+local+109.191.109.xxx+port+32840+connected+with+109.191.109.xxx+port+5001
[+ID]+Interval+++++++Transfer+++++Bandwidth
[++3]++0.0-+5.0+sec++4.72+GBytes++8.12+Gbits/sec

$+iperf+-c+127.0.0.1+1111+-t+5
iperf:+ignoring+extra+argument+--+1111
------------------------------------------------------------
Client+connecting+to+127.0.0.1,+TCP+port+5001
TCP+window+size:+49.7+KByte+(default)
------------------------------------------------------------
[++3]+local+127.0.0.1+port+56482+connected+with+127.0.0.1+port+5001
[+ID]+Interval+++++++Transfer+++++Bandwidth
[++3]++0.0-+5.0+sec++4.62+GBytes++7.94+Gbits/sec|code-block|syntax|javascript|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|I|8|@]|9|@]|A|$E|F]]]|G|$]]

127.0.0.1 is no faster any other local ip. The local ip fast, because it doesn't use physical device and 2-layers.( It never hits your NIC)

<pre><code>iperf -c 109.191.109.xxx 1111 -t 5
iperf: ignoring extra argument -- 1111
------------------------------------------------------------
Client connecting to 109.191.109.241, TCP port 5001
TCP window size: 49.7 KByte (default)
------------------------------------------------------------
[ 3] local 109.191.109.xxx port 32840 connected with 109.191.109.xxx port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0- 5.0 sec 4.72 GBytes 8.12 Gbits/sec

$ iperf -c 127.0.0.1 1111 -t 5
iperf: ignoring extra argument -- 1111
------------------------------------------------------------
Client connecting to 127.0.0.1, TCP port 5001
TCP window size: 49.7 KByte (default)
------------------------------------------------------------
[ 3] local 127.0.0.1 port 56482 connected with 127.0.0.1 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0- 5.0 sec 4.62 GBytes 7.94 Gbits/sec
</code></pre>

blocks|key|5889962|text|这取决于您正在运行的操作系统，但是Windows+2000有一个错误，在环回适配器上的请求会很慢。对你来说有些没用的琐事！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5889963|有关更多信息，请参阅此kb文章。|offset|length|entityMap|0|LINK|mutability|MUTABLE|url|http://support.microsoft.com/kb/294769^0|0|B|4|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@$D|O|E|P|1|Q]]|A|$]]]|F|$G|$5|H|I|J|A|$K|L]]]]

It depends on what OS you're running, but Windows 2000 had a bug in it where requests on the loopback adaptor would be slow. There's some useless trivia for you!

Please see this <a href="http://support.microsoft.com/kb/294769" rel="nofollow noreferrer">kb article</a> for more information.

blocks|key|5890290|text|如前所述，至少在Linux机器上，本地主机和任何其他本地地址都绕过NIC驱动程序--它直接由内核IP堆栈(sidenote:许多以太网硬件MAC根本无法读取传出数据包)提供服务。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5890291|在回环界面上可以达到什么速度？我通过iperf3+-s+&+iperf3+-c+localhost在以下机器上运行了一些测试：|offset|length|style|CODE|5890292|旧英特尔i7-860@2.8+GHz实现23+Gb/s|unordered-list-item|5890293|最新英特尔奔腾G+3260@3.3+GHz实现26+Gb/s|5890294|Ryzen+7+1700@3.0+GHz实现29.4+Gb/s|5890295|上述三台机器的CPU利用率约为150%25+(即:使用了1.5个核心)。一个更快的处理器(具有更高的单线程速度)显然会提供更好的性能。无论如何，在这种速度下，内存复制操作是一个重要的瓶颈:使用“零拷贝传输”(iperf3+-Z+-c+localhost)在Ryzen机器上重新运行相同的测试，导致>38+Gb/s。|entityMap^0|0|I|V|0|0|0|0|2U|M^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@$D|T|E|U|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|J|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|J|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|Y|8|@$D|Z|E|10|F|G]]|9|@]|A|$]]]|Q|$]]

As stated above, on Linux machine at least, both localhost and any other local address bypasses the NIC drivers - it is directly served by the kernel IP stack (sidenote: many ethernet hardware MAC are simply not capable of reading back an outgoing packet).
What speed can be achieved over a loopback interface? I run some test via <code>iperf3 -s &amp; iperf3 -c localhost</code> on the following machines:
<ul>
<li>an old Intel i7-860@2.8 GHz achieves 23 Gb/s</li>
<li>a more recent Intel Pentium G3260@3.3 GHz achieves 26 Gb/s</li>
<li>a Ryzen 7 1700@3.0 GHz achieves 29.4 Gb/s</li>
</ul>
All three machines above had a CPU utilization of about 150% (ie: 1.5 cores were used). A faster processor (with higher single-thread speed) will obviously give greater performance. Anyway, at these speed memory copy operations are a significant bottleneck: re-running the same test on the Ryzen machine using a &quot;zero-copy transfer&quot; (<code>iperf3 -Z -c localhost</code>) resulted in &gt;38 Gb/s

blocks|key|5890034|text|我宁愿说你是从它的名字中找到你的答案。其名称是：“Loopback地址”，这本身意味着网络从来不干预进程，并且请求本身是在本地循环回来的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|entityMap^0^^$0|@$1|2|3|4|5|6|7|C|8|@]|9|@]|A|$]]]|B|$]]

I'd rather say that you find your answer in it's name itself. The name says: "Local Loopback Address", which in itself means that the network never intervenes in the process and the request is in itself looped back locally.

blocks|key|643534|text|如果你在Linux上..。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|643535|输入"ifconfig+-a“作为根..。|643536|注意所有NICs...notice上的“中断”行--在"lo"...that上没有“中断”行，这意味着它甚至没有一个中断分配给它，所以非常快;-)|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|H|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|I|8|@]|9|@]|A|$]]]|F|$]]

If you are on Linux...

type in "ifconfig -a" as root...

Notice the "interrupt" line on all NICs...notice there is no "interrupt" line on "lo"...that means it does not even have an interrupt assigned to it, so pretty darn fast ;-)

blocks|key|643578|text|本地主机“本地回送”运行速度与CPU、RAM和芯片组(SATA、IDE等)和计算机的其他本地物理限制一样快。在USB2.0硬盘上的本地主机将产生480+Mbps或更低的速度，因为您正在使用本地硬盘的总线通过本地主机运行本地USB服务器。另一方面，如果您使用的是SSD或每秒产生100千兆字节的数据速率和系统总线，能够处理计算机上的其他活动，那么它将是快速的。没有实际的硬性限制。CPU上处理TCP数据包的开销很小，但即使是i9-10900K+cpu也可能仅限于以低于45.8G/秒的速度运行的数据。萨塔给你的限制是6+Gbps。基于PCIe+x16的SSD可以达到每秒超过60+GBytes的速度！！PCIe+6.0规格把蛋糕带到超过120千兆字节的每一个方向！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|643579|对于本地主机的速度，没有人能具体说明一个单数。有几个因素将影响实际测量的速度，这取决于您的计算机和操作系统及其他软硬件对系统的影响。上面给出的这些数字是理论上的限制，不一定是实际性能的衡量。瓶颈是计算机中最薄弱的环节。通常，数据进出计算机硬盘的速度，有时还可以缓存在RAM中，以提高速度，但这并不总是一件容易的事情，也不是每个操作系统都很容易/可用的选项。|643580|如果您使用的是基于SATA的驱动器，则可能会产生小于10+based+T的性能。如果您使用的是M.2驱动器，您可能会超过该性能。在PCIe+x16总线速度上运行的SSD将产生每秒40G以上的性能，但是您的CPU和内存总线将施加其自身的限制以及整个系统总线。与本地主机回送进程的操作相关的最慢的总线是除了CPU本身之外的最限制因素，CPU本身可能会加载一些可以影响数据速率的内容。i5将比i9-10900K的cpu限制得更多。|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|H|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|I|8|@]|9|@]|A|$]]]|F|$]]

Localhost &quot;local loopback&quot; runs as fast as your CPU, RAM, and chipset (SATA, IDE, etc.), and other local physical limits of the computer. Localhost off a USB 2.0 Hard drive will yield maybe 480 Mbps or less because of the bus of the local hard drive that you are using to run the local webserver via localhost. On the other hand, if you are using SSD or something yielding 100 Gigabytes per second per direction data rate and system bus capable of handling that with other activities on the computer, then it will be fast. There is no actual hard set limit. There is a little overhead on the CPU to process the TCP packet stuff but even an i9-10900K cpu maybe limited to data running at some speed less than 45.8 Gigabytes per second. SATA gives you limits of like 6 Gbps. PCIe x16 based SSD could go to speeds of over 60 GBytes per second per direction!! PCIe 6.0 specs takes the cake to over 120 Gigabytes per direction !!!!
No one can specifically state a singular number as to how fast localhost will be. Several factors will impact the actual measured speed and that is dependent on your computer and the impact of OS and other software and hardware on the system. These numbers given above are theoretical limits not necessarily actual performance measured. The bottleneck is the weakest link in your computer. Usually the speed of data coming to and from your hard drive on the computer and sometimes, you can cache in RAM for some speed improvement but that isn't always an easy thing or an easily/available option for every OS.
You will likely yield less than 10GBase-T performance if you are using a SATA based drive. If you are using an M.2 drive, you might beat that performance. SSDs running on a PCIe x16 bus speed will yield performance above 40gigabits per second but your CPU and memory bus will impose its own limits as well as the overall system bus. The slowest bus that is involved with the operation of localhost loopback process is your most limiting factor other than the CPU itself which maybe loaded down with stuff which can effect data rate. An i5 will be more limiting than the an i9-10900K cpu.

I wonder if it is tied to my NIC at all or if the OS or driver intercepts and immediately returns data sent to the loopback address?

Does the signal actually travel to my NIC then the NIC returns it?

How fast is 127.0.0.1?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我想知道它是否与我的NIC连接在一起，还是操作系统或驱动程序拦截并立即返回发送回环地址的数据？信号会传递到我的NIC然后NIC会返回它吗？

问127.0.0.1有多快？
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