Korleis auke TCP listen queue lengde for Linux?

[siDDis]

Many web admins think there are two main types of performance bottlenecks for a web server, the raw data rate of the network connection, and the CPU usage on the server machine. In fact there is a third common bottleneck that's still fairly obscure. If you run into this limit you may find that your web server isn't using much CPU, your network link isn't particularly full, and yet there are consistent complaints of timeouts and "connection refused" errors. It can be a very frustrating situation.

 

Here's the deal: most versions of Unix have very short pending-connection queues. This queue is for connections waiting to be accept()ed, and typically it's of length 5. This puts a severe limit on how many connections/second the server can handle - if one comes in while the queue is full, it gets dropped on the floor and the client gets "connection refused". With only 5 slots in the queue, you'll start to see this behavior at around 3 connections/second. thttpd tries to minimize the effect of this limit by accepting new connections as fast as possible, and saving them in its own internal higher-capacity queue for later processing. Even so, for best performance you really want to make the system's queue longer, more like 32, which will handle maybe 10 to 20 connections/second.

 

Er den 5 i Ubuntu? Korleis sjekke og endre?