Is your NIC using TOE or a kernel based TCP/IP stack.

TCP requires the window size to match the B/W delay product.  By default, it is only set to support high B/W LAN or low B/W WAN.   If you have a high B/W WAN, which you would need for RDMA, then you need to increase the TCP buffers and window size settings accordingly.   If it is TOE, then you will be constrained by  whether they expose these settings and whether there is sufficient memory on the card to  reach your B/W delay product.

From: ewg-bounces-ZwoEplunGu1OwGhvXhtEPSCwEArCW2h5@public.gmane.org [mailto:ewg-bounces-ZwoEplunGu1OwGhvXhtEPSCwEArCW2h5@public.gmane.org] On Behalf Of Tanin
Sent: 04 March 2011 01:21
To: linux-rdma; ewg-ZwoEplunGu1OwGhvXhtEPSCwEArCW2h5@public.gmane.org
Subject: [ewg] iWARP tuning

Dear all,

            We had conducted some tests on long distance data transfer using iWARP. But the performance is bad. Does anyone has some idea on how to tune the iWARP for better performance? Does iWARP support paralell data transfer? Does the buffer size of the card tunable?

Thanks!

--

Best regards,

-----------------------------------------------------------------------------------------------
Li, Tan
PhD Candidate & Research Assistant,
Electrical Engineering,
Stony Brook University, NY

Personal Web Site: https://sites.google.com/site/homepagelitan/Home

Email: fanqielee-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org