Kirc Gover wrote:
Hi Gary, Thanks for your response.
Yes, the bus architecture would be either PCI-X or PCI-Express. Host CPU would
be a high performance multi-core such as Xeon and NICs would be Intel.
One of my concern is on the native forwarding capability of FreeBSD OS and the execution
of critical userland processes. I have experience before that a FreeBSD box configured as
router appears to slow down the userland processes when the traffic load is high. I have
verified this lately on 6.1, running on Athlon64 with 1G NIC cards with PF and ALTQ
(queuing) enabled. I'm not so sure if this is caused by PF or ALTQ. Looking at the
processes using top, it could see that "swi(x) net" process is almost as near
100% cpu utilization. At this state, the box can still forward traffic (not sure yet if
the was a change in throughput) but I could notice the userland processes to be very
slow, like invoking any command from the shell (e.g. ls) will take so long to be
executed and completed. Is this a know limitation or bug?
I'm probably not the best person to address that, but its my
understanding that interrupts will preempt other activity such as
userland processing. Since there is often a requirement to service
interrupts as a matter of priority (e.g. before the receive buffer in
the NIC overflows) I'm not sure theres a way around it. The performance
improvements in 7.x, especially relating to multi-core/CPU environments
might help. The complexity of the PF / ALTQ rules can also have an
impact, although I'm a little surprised that they counted towards
interrupt activity, which your message seems to imply.
Gary
P.S. Please don't top post.
Thanks a lot.
Kirc
Gary Palmer <[EMAIL PROTECTED]> wrote: On Fri, Sep 07, 2007 at 03:06:54AM
+1000, Kirc Gover wrote:
We are in the stage of planning and research for a commercial development of an
edge router that will be based mostly on OpenSource software. I would like to
solicit for information and recommendation if FreeBSD is a suitable OS. The
router is expected to withstand forwarding of sustained traffic from 10Mbps to
1Gbps and maybe more than that. Are there any known limitations of FreeBSD in
terms of architecture and performance? Can I just take out a FreeBSD as is and
put it with the hardware without any specific or major refinements in its code?
I'm very much concerned with its capability in forwarding heavy sustained
traffic. Packet loss should be at minimum and critical userland processes
should working normally even under heavy load. Are there any known specific
limitations of FreeBSD? I have browsed through the archives and found a lot of
hangups, deadlocks and freeze issues. What is the usual or minimum hardware
requirement? Is soekris box enough, or dual core or ASIC
based platforms? I'm aware that there are so many FreeBSD based routers and
network based devices in the market. Is this a way to go over realtime and
embedded OS such as VxWorks and others (mostly commercial) without putting the
licensing cost in picture? I really appreciate any help, suggestions and
recommendations. More power to FreeBSD!
Kirc,
There are two factors to consider:
- bus architecture (PCI, PCI-X, PCI-Express, etc) will dictate the
maximum throughput in bits/sec. Allow some overhead for bus arbitration
activities, and remember that the packet crosses the bus twice, once
on the inbound leg and once on the outbound leg.
- Host CPU (and perhaps to a limited extent the interface cards used)
will dictate the packets per second (PPS)
Most commercial routers run out of packets per second (in real-world
situations, not lab mockups) long before the theoretical maximum
throughput is achieved. Thinks like ICMP ping packets and TCP RST
packets are small (less than 100 bytes usually) but normally take as much
CPU to process & route as a 1500 byte (or larger) packet.
The more you put in the processing path (e.g. packet filters, complex
routing tables) the more you reduce the PPS.
Gary
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