Dear Rick,
First thank you SO SO SO MUCH for your kindly telling. It's really useful
for me to solve problems.
From the test summary listed, I can see that we have similar systems except
that you are using MontaVista while I am using the general open-source
kernel. Also I enabled all the features which could improve the
performance, including DRE, CSUM offload and SGDMA,etc.
- Are Checksum offload, SGDMA, and DRE enabled in the plb_temac?
Yes. All features are enabled.
- Are you using the TCP_SENDFILE option of netperf? Your UDP numbers are
similar already to what we saw in Linux 2.6, and your TCP numbers are
similar to what we saw *without* the sendfile option.
Perhaps no. I just understand that sendfile option is so important to
improve performance. At first I thought it will achieve a same performance
with TCP_STREAM, until I saw the article to explain how to use sendfile()
to optimize data transfer. So I will try this soon.
After some reading of the articles on performance improving, here come
other problems. So I will appreciate you so much if you can clarify them
for me.
1. Results are from PLB_TEMAC, not GSRD. You would likely see similar
throughput rates with GSRD and Linux.
Problem 1: From the website for GSRD, I know that it uses a different
structure than PLB, where a Multi port mem controller and DMA are added to
release the CPU from move data between Memory and TEMAC. So can GSRD
achieve a higher performance than PLB_TEMAC, or similar performance like
what you said above? If their performance is similar, what's the advantage
for GSRD? Could you please explain some differences between these two
structures?
2. Assuming you have everything tuned for SGDMA based on previous emails,
I would suspect the bottleneck is the 300MHz CPU *when* running Linux. In
Linux 2.6 we've not spent any time trying to tune the TCP/Ethernet
parameters on the target board or the host, so there could be some
optimizations that can be done at that level. In the exact same system we
can achieve over 800Mbps using the Treck TCP/IP stack, and with VxWorks it
was over 600Mbps.
Problem 2. I read XAPP546 of High performance TCP/IP on xilinx FPGA devices
using the Treck embedded TCP/IP stack. I notice that the features of Treck
TCP/IP stack include: Zero-copy send and receive, Jumbo-frame support, CSUM
offload, etc. which could achieve a much higher performance than not using
it. However in the Xilinx TEMAC core V3.00, these features are all
supported: Zero-copy is supported by sendfile() when using Netperf;
Jumbo-frame is also supported; CSUM offload and DRE are also supported by
the hardware. So does this mean I can achieve a similarly high performance
with PLB_TEMAC V3.00 and without Treck TCP/IP stack? I mean if all the
features of Treck stack have been included in the PLB_TEMAC cores, what's
the use for Treck stack?
Maybe my questions are a little stupid. But I am really confused on them.
So thank you so much if you can explain them to me. Thanks a lot.
BR
Ming
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