Messages in this thread | | | Date | Tue, 05 Oct 1999 18:07:05 -0700 | From | Zachary Amsden <> | Subject | Re: predictable IP ID |
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>IMHO it's not possible to lockup a machine due OOM using an userspace >application. This because userspace will be swapped out or will generate >faults and you'll get a SIGKILL before you'll have filled all the memory >with vmas. > >The network instead doesn't run from userspace and data structures gets >allocated per irq demand and you can't kill the source of the memory >allocation as it's not on your machine. > >Andrea
Which is yet another good reason to implement early demux/lazy processing. Basically, all packet processing is punted over to the socket structure from the device driver. If the socket queue is overfull, we drop the packet. If we get a packet for an unbound service, we can either drop or pass it along to a kernel response thread. If we get a new connection request, it gets delivered to the listen()ing socket. By tailoring the backlog and priorities of each of these threads, we can tailor overload charateristics of the box for optimal performance. With some protocols it may be possible to do early demux in hardware, without even interrupting the CPU for flood attacks. Of course, network performance will still suffer due to collisions, but your box won't fall over and die.
Zach Amsden zamsden@engr.sgi.com
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