Hi, I am seeking advice on how to best send out huge
number of packets on a gigabit ethernet interface. I
am using kernel 2.4.19. I try to send out as many as
possible 15Kbyte-long ethernet packets to try to
utilize the giga-bit/sec bandwidth. My CPU is really
fast (2 GHz) amd I dump the packets to the interface
in a tight loop in user space. However, I can only
reach around 400 Mbits/sec before the packets get
dropped. The queue discipline (qdisc) seems to be
responsible because the queue length (txqueuelen) is
only 100 by default, and the queue just cannot store
so many packets at once. I can eliminate the packet
drop by raising the queue length to somewhere like
60000 but that is not practical because it uses too
much memory. It seems I need some delay between
sending packets but I cannot sleep for less than 10 ms
(1/Hz) in user space and 10 ms is too long.
I am using raw socket bypassing the IP stack and my
NIC is the Intel Pro1000 (using the e1000.o driver).
What is the best way to send raw ethernet packets,
reaching gigabit range withuut packet drop on Linux?
Thanks for any advice.
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Lk Overrun wrote:
> Hi, I am seeking advice on how to best send out huge
> number of packets on a gigabit ethernet interface. I
> am using kernel 2.4.19. I try to send out as many as
> possible 15Kbyte-long ethernet packets to try to
> utilize the giga-bit/sec bandwidth. My CPU is really
> fast (2 GHz) amd I dump the packets to the interface
> in a tight loop in user space. However, I can only
> reach around 400 Mbits/sec before the packets get
> dropped. The queue discipline (qdisc) seems to be
> responsible because the queue length (txqueuelen) is
> only 100 by default, and the queue just cannot store
> so many packets at once. I can eliminate the packet
> drop by raising the queue length to somewhere like
> 60000 but that is not practical because it uses too
> much memory. It seems I need some delay between
> sending packets but I cannot sleep for less than 10 ms
> (1/Hz) in user space and 10 ms is too long.
>
> I am using raw socket bypassing the IP stack and my
> NIC is the Intel Pro1000 (using the e1000.o driver).
>
> What is the best way to send raw ethernet packets,
> reaching gigabit range withuut packet drop on Linux?
> Thanks for any advice.
Make sure the e1000 driver is tuned, try insmodding it with:
TxDescriptors=1024 RxDescriptors=4096
Also, in your user-space app, check the return code of your
packet-sending call. That can let you know that the kernel
dropped it, and that you need to re-send.
How do you know you are dropping packets? (Ie, are you also
reading on another machine?) Usually it's read that drops
more packets than write.
Good luck,
Ben
>
>
>
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>I try to send out as many as
>possible 15Kbyte-long ethernet packets to try to
> utilize the giga-bit/sec bandwidth
If you just want to generate packets then try pktgen in Linux-2.4.19:
CONFIG_NET_PKTGEN
This module will inject preconfigured packets, at a configurable
rate, out of a given interface. It is used for network interface
stress testing and performance analysis. If you don't understand
what was just said, you don't need it: say N.
Documentation on how to use the packet generator can be found
at <file:Documentation/networking/pktgen.txt>.
This code is also available as a module called pktgen.o ( = code
which can be inserted in and removed from the running kernel
whenever you want). If you want to compile it as a module, say M
here and read <file:Documentation/modules.txt>.