Freebsd IP Forwarding performance (question, and some info)
[7-stable, current, em, smp]
brde at optusnet.com.au
Mon Jul 7 10:00:22 UTC 2008
On Mon, 7 Jul 2008, Andre Oppermann wrote:
> Ingo Flaschberger wrote:
>> I don't think you will be able to route 64byte packets at 1gbit wirespeed
>> (2Mpps) with a current x86 platform.
> You have to take inter-frame gap and other overheads too. That gives
> about 1.244Mpps max on a 1GigE interface.
What are the other overheads? I calculate 1.644Mpps counting the inter-frame
gap, with 64-byte packets and 64-header_size payloads. If the 64 bytes
is for the payload, then the max is much lower.
>> I hoped to reach 1Mpps with the hardware I mentioned some mails before, but
>> 2Mpps is far far away.
>> Currently I get 160kpps via pci-32mbit-33mhz-1,2ghz mobile pentium.
> This is more or less expected. PCI32 is not able to sustain high
> packet rates. The bus setup times kill the speed. For larger packets
> the ratio gets much better and some reasonable throughput can be achieved.
I get about 640 kpps without forwarding (sendto: slightly faster;
recvfrom: slightly slower) on a 2.2GHz A64. Underclocking the memory
from 200MHz to 100MHz only reduces the speed by about 10%, while not
overclocking the CPU by 10% reduces the speed by the same 10%, so the
system is apparently still mainly CPU-bound.
> NetFPGA doesn't have enough TCAM space to be useful for real routing
> (as in Internet sized routing table). The trick many embedded networking
> CPUs use is cache prefetching that is integrated with the network
> controller. The first 64-128bytes of every packet are transferred
> automatically into the L2 cache by the hardware. This allows relatively
> slow CPUs (700 MHz Broadcom BCM1250 in Cisco NPE-G1 or 1.67-GHz Freescale
> 7448 in NPE-G2) to get more than 1Mpps. Until something like this is
> possible on Intel or AMD x86 CPUs we have a ceiling limited by RAM speed.
Does using fa$ter memory (speed and/or latency) help here? 64 bytes
is so small that latency may be more of a problem, especially without
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