From:
address@hidden
[mailto:address@hidden On Behalf Of address@hidden
Sent: Tuesday, January 22, 2008
2:14 PM
To: Mailing list for lwIP users
Subject: Re: [lwip-users] Which
opt.h options effect TCP receive throughput?
Bill,
Now
that you have a baseline, why not try sending PPC-->PPC and PC-->PC to
get an idea of where any slowness might be? You might not even want to
store the received data, just drop it on the floor.
Andy
"Bill Auerbach"
<address@hidden>
Sent
by: address@hidden
01/22/2008 02:09 PM
Please
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[lwip-users] Which opt.h options effect TCP
receive throughput?
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Hello,
I’m still benchmarking lwIP TCP (PPC Power Arch)
while receiving 2MB files to the PPC. I’m using raw api (call
backs) and NO_SYS. 98% of the processor is processing lwIP timers and
checking for Ethernet packets and the callbacks are doing the work. I
have not moved to Jumbo (Huge) frames yet – I want to get standard
packets as fast as possible.
Interestingly, copying from the pbufs to contiguous memory
is using about 10% of the bandwidth *including*
using DMA to move the data (it was 40% with memcpy and 20% with an optimized
memcpy).
Right now I’m at 464MbS for a 2MB transfer.
Finally the question of the subject line: Which lwIP options most effect
receive throughput? Is it just these, which I’ve set as follows:
#define TCP_WND
(64*1024-1)
#define TCP_MSS
(8*1024)
One thing I notice is there is an ACK sent for every 2 packets
received. Does this sound right? (2874 received, 1437 sent).
I tried a direct point to point link (PC to PPC box) with
no change in the results. So the router is giving this burst everything
– in fact I see no intervening packets in wireshark from the first to
last TCP packet in my transfer (this surprised me actually).
What is the theoretical limit with TCP? Is it the PC
slowing things down, or am I simply close to “as good as it gets”?
Thanks,
Bill Auerbach
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