dpcpp program performance gets drop by adding compile option '-g'

[Jim]

Hi all

I found dpcpp program performance gets drop by adding compile option '-g'.

And I also test the related cuda program, nvcc does not have this problem.

The program source code has been uploaded.

The compile cmdline is :

dpcpp -o a -O2 ./convSep_nocg.dp.cpp

dpcpp -o a_g -g -O2 ./convSep_nocg.dp.cpp

Program 'a_g' spend near 2x time vs 'a'. 

# ./a 10240 10240 1000
[./a] - Starting...
Image Width x Height = 10240 x 10240

Allocating and initializing host arrays...
Allocating and initializing CUDA arrays...
Running GPU convolution (1000 identical iterations)...

convolutionSeparable, Throughput = 1321.5942 MPixels/sec, Time = 0.07934 s, Size = 104857600 Pixels, NumDevsUsed = 1, Workgroup = 0

Reading back GPU results...

Checking the results...
 ...running convolutionRowCPU()
 ...running convolutionColumnCPU()
 ...comparing the results
 ...Relative L2 norm: 0.000000E+00

Shutting down...


# ./a_g 10240 10240 1000
[./a_g] - Starting...
Image Width x Height = 10240 x 10240

Allocating and initializing host arrays...
Allocating and initializing CUDA arrays...
Running GPU convolution (1000 identical iterations)...

convolutionSeparable, Throughput = 773.0526 MPixels/sec, Time = 0.13564 s, Size = 104857600 Pixels, NumDevsUsed = 1, Workgroup = 0

Reading back GPU results...

Checking the results...
 ...running convolutionRowCPU()
 ...running convolutionColumnCPU()
 ...comparing the results
 ...Relative L2 norm: 0.000000E+00

Shutting down...

OS Version: Ubuntu 18.04.3 LTS

linux-kernel: 4.15.18

oneAPI Basekit Version: 2021.1-beta06

CPU: Intel(R) Xeon(R) CPU E3-1585 v5 @ 3.50GHz

GPU: Intel Corporation Iris Pro Graphics P580

[PrasanthD_intel]

Hi Jim,

When we use -g debug flag in dpcpp, it generates debug information for both host as well as device part of the code. 

Enabling -g option creates another section called debug section. So this will, in turn, create overhead during compilation, hence there could be a considerable increase during run time.

For more information, you refer to this link.

https://software.intel.com/content/www/us/en/develop/documentation/get-started-with-debugging-dpcpp-linux/top.html

However, when -g flag is passed to nvcc compiler it generates debug information only for the host. To generate debug information for the device there is a different flag that needs to be passed to the nvcc compiler.

Regards

Prasanth

[GouthamK_Intel]

Hi Jim,

Could you please let us know if your issue is resolved.

If not do let us know. So that we will be able to help you regarding the same.

Regards

--Goutham

[PrasanthD_intel]

Hi Jim,

This issue has been resolved and we will no longer respond to this thread. If you require additional assistance from Intel, please start a new thread. Any further interaction in this thread will be considered community only

Regards

Prasanth