Re: [lwip-users] Which opt.h options effect TCP receive throughput?

[Andrew_Kunz]

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>
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01/22/2008 02:09 PM

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Subject	[lwip-users] Which opt.h options effect TCP receive throughput?

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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