Re: tcp/ip performance problem

[Pekka Savola]

On Wed, 1 Oct 2008, Vitaly Ivanov wrote:
> We have solved this problem. We had tuned TCP/IP stack in Linux Kernel
> but it hadn't helped us because there was very law value backlog in
> listen function
> int listen(int sockfd, int backlog);
> This function is used in nginx and lighttp demons. In nginx this value
> had been set to 511 and in lighttp to 1024. We set both value to 65535
> or -1 and solve our problem. Now we have about 700Mbit per second
> instead 70.

Good catch.  I wonder if there is any way to figure out the listen 
backlog (except using strace) for a socket, e.g. using a system level 
tool?

> But now we got another trouble - our server under heavily load because
> ksoftirqd use 100% CPU. We suppose that this process is "bottle-neck".
> Can we tune this process?

It smells like you're getting so many packets the CPU is filled by 
IRQs.  Take a look at this and maybe google around for "polling" and 
"NAPI":

http://kb.pert.geant2.net/PERTKB/InterruptCoalescence


--
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings
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