I have problem with clear GPU memory

29 次查看（过去 30 天）
Vitaly Bur
Vitaly Bur 2020-10-29
评论： Vitaly Bur 2020-11-2
After executing this code, the GPU memory is use by 2 GB. Only the D matrix in GPU memory...
A=fix(gpuArray(rand(1,1000))*99)+1;
B=fix(gpuArray(rand(1,1000))*99)+1;
C=gpuArray(rand(100000,100));
E=C(:,A);
F=C(:,B);
D=E.*F;
clear E F C A B
However, if I execute this code.
D=gpuArray(rand(100000,1000));
There we see D matrix (same size) in GPU memory, but now it only use 1 GB of GPU memory. Why is there a difference? and how to clear the memory in the first variant?
  2 个评论
Raymond Norris
Raymond Norris 2020-10-29
Hi Vitaly,
I don't have a GPU at my disposal. Your code, A..D, consumes 2.37 GB. D alone is 763 MB. So I think that aligns with what you're seeing, except I'm not sure why you think only D is in the GPU memory.
Have you called reset to clear the GPU?
reset(gpuDevice)
Are you using nvidia-smi to check if the memory goes up and down?
Raymond
Vitaly Bur
Vitaly Bur 2020-10-30
编辑：Vitaly Bur 2020-10-30
Hi, Raymond!
If add in first code a clear D - the GPU memory is reset to 0.
I see the difference between the variants under the same conditions - before starting the program, of course, I reset memory to 0 and everything is cleared to 0.
When the program ends or when I interrupt its execution, everything is reset to 0. The problem is that along with D, a copy of it is stored in memory, or something else that I don't need.
I using the task Manager: GPU memory.
If I use CPU such problem is not present.
look at the charts. You can see that clear works on the CPU and clear memory. But the clear command doesn't work on the GPU. On the GPU, memory is cleared when all variables are cleared. So it shouldn't be?

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

Joss Knight
Joss Knight 2020-11-2
MATLAB does not clear all GPU memory unless all variables are released because allocating memory is a performance bottleneck. So MATLAB instead pools memory for later allocations.
To force the GPU to release all memory, you can call reset(gpuDevice).
  7 个评论
显示 5更早的评论
Joss Knight
Joss Knight 2020-11-2
Oh I see now. This is just because D hasn't been evaluated yet, which means E and F are still being held in memory, as is C because E and F are just slices of C which means it's being held in memory until we attempt to modify them. We use a lazy evaluation optimization and you haven't actually required D to be used or displayed. Insert gather(D) or wait(gpu) to force evaluation, and the memory will be freed.
Vitaly Bur
Vitaly Bur 2020-11-2
Thanks.A miracle happened - the use of wait(gpu) solved the problem.
gpu=gpuDevice();
reset(gpu);
gpu=gpuDevice();
disp(gpu)
feature('GpuAllocPoolSizeKb',0);
A=fix(gpuArray(rand(1,1000))*99)+1;
B=fix(gpuArray(rand(1,1000))*99)+1;
C=gpuArray(rand(100000,100));
E=C(:,A);
F=C(:,B);
D=E.*F;
wait(gpu)
pause
clear E F C A B
pause
clear D
pause
D=gpuArray(rand(100000,1000));
pause

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 GPU Computing in MATLAB 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by