[openib-general] RDMA Read performance

[Grant Grundler]

On Thu, Aug 18, 2005 at 01:05:49PM -0600, Galen Shipman wrote:
> Hello,
> 
> I am using RDMA READ for an internal application and I am seeing 
> problems with performance on OpenIB. I am not seeing the same 
> performance problems on like hardware using Mellanox VAPI. Perhaps I am 
> doing something silly.  Attached is a patch to rdma_bw.c where I am 
> seeing only ~192MB/sec which should be closer to 950MB/sec.

Galen,
Normally patches should be attached as "plain text" and
not as:
[-- Attachment #2: rdma_bw_diff --]
[-- Type: application/octet-stream, Encoding: 7bit, Size: 2.4K --]
 
[-- application/octet-stream is unsupported (use 'v' to view this part) --]

The patch also has "white space damage" - ie white space
changes that don't belong in the patch. Just a distraction.


> Any help or ideas are appreciated.

I can try it out on my boxes.
ISTR I was getting ~750 MB/s on the regular rdma_bw.c code.
I agree 192 MB/s seems really low for any PCI-X box.

I have to wonder if your version (using reads) is not getting the
parallelism that writes could acheive. 192MB/s sounds more like
ping-pong with large pages.
Could you run the ibv_pingpong test and report what that gets?

(It's under .../src/userspace/libibverbs/examples/)

grant