CUDA 4 RC2 Performance Lost

[ikidntu]

Dear Cuda Team,

My application got a performance loss after installing the new driver so I tried to write a smaller program to reproduce the effect. Could you help me investigating the reason ?

The program basically do reduction on both gpu, then send result from gpu1 to gpu0 and reduction with its own result. I separate the result into multiple part for overlapping the computation and communication and synchronize using event and stream.

I attached the code with the post. I use 2 x S2050 with ECC off on redhat 2.6.18-128.1.14.el5

Compile: “nvcc -arch=sm_20 test.cu -o test”

Run:

on RC2 :

cat /proc/driver/nvidia/version

NVRM version: NVIDIA UNIX x86_64 Kernel Module 270.40 Sat Mar 26 13:00:34 PDT 2011

GCC version: gcc version 4.1.2 20080704 (Red Hat 4.1.2-44)

#./test 30000000 > ~/tmp/1

4.71 (sec)

on RC :

cat /proc/driver/nvidia/version

NVRM version: NVIDIA UNIX x86_64 Kernel Module 270.27 Fri Feb 18 17:36:20 PST 2011

GCC version: gcc version 4.1.2 20080704 (Red Hat 4.1.2-44)

#./test 30000000 > ~/tmp/2

3.96 (sec)

#diff ~/tmp/1 ~/tmp/2

… same result

Thanks in advance !
test.cu (3.55 KB)

[njuffa]

Since you already prepared a repro case, it would be helpful if you could file a bug. Thanks!

[ikidntu]

Since you already prepared a repro case, it would be helpful if you could file a bug. Thanks!

Sorry, how could I file a bug ?

Couldn’t found it in The Official NVIDIA Forums | NVIDIA

[ikidntu]

I have submitted the bug through nvdeveloper.nvidia.com. However I couldn’t find the “Bug Status” mentioned in the email. Any idea where it is?