On 2018-10-15 12:13, Tom Herbert wrote:
> On Mon, Oct 15, 2018 at 12:06 PM, Templin (US), Fred L
> <fred.l.temp...@boeing.com> wrote:
>
>> Hi Tom,
>>
>> ...
>> From what I saw when I was working with iperf3. By default, it uses 8KB
>> UDP datagram sizes when it runs on Ubuntu. By setting the UDP datagram
>> size to a smaller value (i.e., one that needs less IP fragmentation) it shows
>> a performance decrease. By setting the UDP datagram size to a larger value
>> (i.e., one that needs more IP fragmentation) it shows a performance increase.
> Yes, this because it's better to wake application once than mutiple
> times for smaller packets.
Smaller packets have lower throughput because of many other per-packet
overheads which include the header length overhead relative to the
payload and setup costs for DMA and IP checksum, etc.
The issue of waking the app matters less if using polling, which is more
typical than relying on interrupts for high-speed networking.
Joe
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