Video Memory Allocation

[amitsaha]

How do I find out using a command or reading from a file, what is the allocation for the video memory is? Yes, I can subtract the available memory from my total memory. Any other solution?

Also, how can I change it?

Thanks.

[Deteros]

Hi amitsaha,

> How do I find out using a command or reading from a file,
> what is the allocation for the video memory is?

You could read /boot/config.txt and look for
gpu_mem=, gpu_mem_256= or gpu_mem_512=
If not existing, then the default is 64,
compare http://elinux.org/RPi_config.txt

I assume the GPU memory is set during boot
and cannot be changed during runtime.

[amitsaha]

Hi amitsaha,

> How do I find out using a command or reading from a file,
> what is the allocation for the video memory is?

You could read /boot/config.txt and look for
gpu_mem=, gpu_mem_256= or gpu_mem_512=
If not existing, then the default is 64,
compare http://elinux.org/RPi_config.txt

I assume the GPU memory is set during boot
and cannot be changed during runtime.

Ah. Thanks a lot. I could do that by setting the gpu_mem_512 variable. By default, it was allocating 64 MB as shared memory.

Another query: Now, I have 466 MB for OS memory and 32 MB for shared graphics. Where am I missing the remaining 14 MB of my 512 MB memory?

Thanks for any ideas.

[Deteros]

Hi amitsaha,

> Another query: Now, I have 466 MB for OS memory and 32 MB for shared graphics.
> Where am I missing the remaining 14 MB of my 512 MB memory?

Available memory is 477648k = 466 MByte.

If you study the kernel log messages (on my system in /var/log/messages)
you'll find (I have the same config then you: 512 MB with 32 MB shared graphics):

[ 0.000000] Memory: 480MB = 480MB total
[ 0.000000] Memory: 477476k/477476k available, 14044k reserved, 0K highmem
-> Linux reserves 14044k
...
[ 8.554283] Freeing init memory: 172K
-> frees 172k, thus free memory is now 477476k+172k = 477648k - same as above.

[amitsaha]

Hi Deteros,

Hi amitsaha,

> Another query: Now, I have 466 MB for OS memory and 32 MB for shared graphics.
> Where am I missing the remaining 14 MB of my 512 MB memory?

Available memory is 477648k = 466 MByte.

If you study the kernel log messages (on my system in /var/log/messages)
you'll find (I have the same config then you: 512 MB with 32 MB shared graphics):

[ 0.000000] Memory: 480MB = 480MB total
[ 0.000000] Memory: 477476k/477476k available, 14044k reserved, 0K highmem
-> Linux reserves 14044k
...
[ 8.554283] Freeing init memory: 172K
-> frees 172k, thus free memory is now 477476k+172k = 477648k - same as above.

Thank you for your reply. I had a feeling that it must be the reserved memory. Thank you for confirming this. I also checked it myself.


Thanks.

[amitsaha]

And this is a great post explaining about the memory allocation: http://winfred-lu.blogspot.com.au/2011/ ... -mips.html

[jamesh]

If you start to use CMA (beta at the moment) then the sharing between Arm and GPU is dynamic- the GPU gives up memory to the Arm and vica versa as required.