I'd like to know the reasons for why the linux kernel (or any other mainstream OS) does not have a feature for zero copy networking ? By zero copy I mean, that an packet/datastream does not get copied for passing to an application in userspace but e.g. uses a memory-pool type of allocator to share the memory between kernel and userspace. I've came up with 3 theory's on my own:
我想知道为什么linux内核（或任何其他主流操作系统）没有零拷贝网络功能的原因？零拷贝我的意思是，没有复制数据包/数据流以传递给用户空间中的应用程序，例如使用内存池类型的分配器来共享内核和用户空间之间的内存。我自己想出了3个理论：
a) I guess there are security concerns. But is there really no way of making memory shared securily between userspace and kernel when they are just used as a buffer ?
a）我猜有安全问题。但当它们仅用作缓冲区时，是否真的没有办法在用户空间和内核之间安全地共享内存？
b) I guess there are stability concerns. But can't we assume that whoever uses zero-copy networking and e.g. needs to instanciate and pass a memory-pool for the kernel call is aware of memory management? Aware enough to avoid leaks ?
b）我猜有稳定性问题。但我们不能假设使用零拷贝网络的人，例如需要instanciate和传递内存池为内核调用是否知道内存管理？意识到足以避免泄漏？
c) It just haven't been done/needed so far. I can't really imagine that nobody requested this feature, as everybody who is using small packet sizes is typically bottlenecked by the "slow" TCP-stack implementation and there are 3rd party tools out there offered for 0-copy networking for usage with special network cards.
c）到目前为止还没有完成/需要。我无法想象没有人要求这个功能，因为每个使用小数据包大小的人通常会受到“慢速”TCP堆栈实施的瓶颈，并且有第三方工具可用于0-copy网络以供特殊用途使用网卡。
Feel free to post any guesses, but please mark whether you are assuming or have a deeper knowledge of the reasons to keep *-quality :-)
随意发布任何猜测，但请标记您是否正在假设或更深入了解保持*质量的原因:-)
1 个解决方案
#1
5
There is 3rd-party zero-copy networking for Linux, it is not a standard feature though.
Linux有第三方零拷贝网络，但它不是标准功能。
Note, that zero-copy with TCP may be inconvenient, because TCP segments carry headers and payload, but applications are only concerned with payload, so that payload but not headers must be copied into a contiguous buffer for your application.
注意，使用TCP进行零拷贝可能不方便，因为TCP段承载头和有效负载，但应用程序只关注有效负载，因此必须将有效负载而不是头部复制到应用程序的连续缓冲区中。
#1
5
There is 3rd-party zero-copy networking for Linux, it is not a standard feature though.
Linux有第三方零拷贝网络，但它不是标准功能。
Note, that zero-copy with TCP may be inconvenient, because TCP segments carry headers and payload, but applications are only concerned with payload, so that payload but not headers must be copied into a contiguous buffer for your application.
注意，使用TCP进行零拷贝可能不方便，因为TCP段承载头和有效负载，但应用程序只关注有效负载，因此必须将有效负载而不是头部复制到应用程序的连续缓冲区中。