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Doesn't look like anyone has really answered your question yet. There are three main reasons the kernel is slow for networking: per-packet dynamic memory alloc

Doesn't look like anyone has really answered your question yet. There are three main reasons the kernel is slow for networking: per-packet dynamic memory allocation, lots of memory copying, and system call overheads. The first two can be improved by modifying the kernel, and I think people are attempting to do this. The system call overheads arise naturally from having the networking code in the kernel. Basically every time you perform a system call the kernel has to save the userspace context, do the system call, and restore the context. This takes time and is bad for cache locality. But as others noted, for most people who aren't cloudflare this doesn't really matter.

acconsta 11y ago
>But as others noted, for most people who aren't cloudflare this doesn't really matter. Aren't most web applications I/O bound? The Arrakis team sped up Memcached and Haproxy quite a lot by bypassing the kernel. It seems like there could be a large market for these techniques as they become easier to use. http://people.inf.ethz.ch/troscoe/pubs/peter-arrakis-osdi14.pdf http://people.inf.ethz.ch/troscoe/pubs/peter-arrakis-osdi14....
- jeffreyrogers 11y ago
  Hmmm, that's a good point. I was thinking more of a typical webapp, but you're probably right that there are certain classes of applications (e.g. caching) that are I/O bound under load.
s1m0n 11y ago
Reason #4: Another problem is that the network kernel was never designed to do internet on the mass scale desired today. Companies like whatsapp devoted lots of time to getting e.g. 2M concurrent TCP connections (considered good) running on a single box, mainly because of the greedy overhead and design of the legacy network kernel. Whereas, in theory it should be possible to have 10M or more concurrent TCP connections on modern average hardware. So from this POV then the legacy network kernel is the bloated memory greedy mess that Java is to software development. See http://c10m.robertgraham.com/p/manifesto.html http://c10m.robertgraham.com/p/manifesto.html

acconsta 11y ago

>But as others noted, for most people who aren't cloudflare this doesn't really matter. Aren't most web applications I/O bound? The Arrakis team sped up Memcached and Haproxy quite a lot by bypassing the kernel. It seems like there could be a large market for these techniques as they become easier to use. http://people.inf.ethz.ch/troscoe/pubs/peter-arrakis-osdi14.pdf http://people.inf.ethz.ch/troscoe/pubs/peter-arrakis-osdi14....

jeffreyrogers 11y ago
Hmmm, that's a good point. I was thinking more of a typical webapp, but you're probably right that there are certain classes of applications (e.g. caching) that are I/O bound under load.

s1m0n 11y ago

Reason #4: Another problem is that the network kernel was never designed to do internet on the mass scale desired today. Companies like whatsapp devoted lots of time to getting e.g. 2M concurrent TCP connections (considered good) running on a single box, mainly because of the greedy overhead and design of the legacy network kernel. Whereas, in theory it should be possible to have 10M or more concurrent TCP connections on modern average hardware. So from this POV then the legacy network kernel is the bloated memory greedy mess that Java is to software development. See http://c10m.robertgraham.com/p/manifesto.html http://c10m.robertgraham.com/p/manifesto.html