Re: Kernel hooks just to get rid of copy_[to/from]_user() and syscall overhead?

[Gianni Tedesco <gianni@ecsc.co.uk>]

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On Fri, 2003-01-10 at 14:45, Mihnea Balta wrote:
> Hi,
> 
> I have to implement a system which grabs udp packets off a gigabit connection, 
> take some basic action based on what they contain, repack their data with a 
> custom protocol header and send them through a gigabit ethernet interface on 
> broadcast.
> 
> I know how to do this in userspace, but I need to know if doing everyting in 
> the kernel would show a considerable speed improvement due to removing 
> syscall and memory copy overhead. The system will be quite stressed, having 
> to deal with around 15-20000 packets/second.

mmap() packet socket interface eliminates the need for system calls when
traffic is coming in at a high rate.  The kernel -> user copy is also
eliminated, but its just replaced with a kernel -> kernel copy :P

You could perhaps also use linux socket filters to minimize the number
of packets you need to evaluate...

Check out this sample code: http://www.scaramanga.co.uk/code-fu/lincap.c

HTH

-- 
// Gianni Tedesco (gianni at scaramanga dot co dot uk)
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