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underwhelmd
Posts: 94
Joined: Fri Jul 08, 2016 10:05 pm
Location: East Coast, Canada

Re: Extra 16M memory on Pi2/Pi3

Wed Aug 02, 2017 3:43 pm

The following is a Pi3 that I just use for kodi. It's running jesse lite, from a USB drive. I made the changes to config and all is well, no crashes.

Code: Select all

[email protected]_three:~ $ uname -a
Linux thing_three 4.9.35-v7+ #1014 SMP Fri Jun 30 14:47:43 BST 2017 armv7l GNU/Linux

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[email protected]_three:~ $ vcgencmd get_mem arm
arm=688M
[email protected]_three:~ $ vcgencmd get_mem gpu
gpu=320M
[email protected]_three:~ $ sudo pico /boot/config.txt
reboot

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[email protected]_three:~ $ vcgencmd get_mem arm
arm=704M
[email protected]_three:~ $ vcgencmd get_mem gpu
gpu=320M
Thank you..

runboy93
Posts: 352
Joined: Tue Feb 28, 2017 1:17 pm
Location: Finland
Contact: Website

Re: Extra 16M memory on Pi2/Pi3

Wed Aug 02, 2017 5:25 pm

underwhelmd wrote:
Wed Aug 02, 2017 3:43 pm
The following is a Pi3 that I just use for kodi. It's running jesse lite, from a USB drive. I made the changes to config and all is well, no crashes.

Code: Select all

[email protected]_three:~ $ uname -a
Linux thing_three 4.9.35-v7+ #1014 SMP Fri Jun 30 14:47:43 BST 2017 armv7l GNU/Linux

Code: Select all

[email protected]_three:~ $ vcgencmd get_mem arm
arm=688M
[email protected]_three:~ $ vcgencmd get_mem gpu
gpu=320M
[email protected]_three:~ $ sudo pico /boot/config.txt
reboot

Code: Select all

[email protected]_three:~ $ vcgencmd get_mem arm
arm=704M
[email protected]_three:~ $ vcgencmd get_mem gpu
gpu=320M
Thank you..
I heard there were some crash with Kodi system, but that seem to be rare case also.

"Extra" 16M is always a bonus, for arm or gpu.

"sudo nano /boot/config.txt"

total_mem=1024

I use Raspbian and I use arm=768 gpu=256 (maybe even 128 is enough...)

SD card overclock + max 1.35GHz or 1.4GHz CPU overclock (aluminum passive cooling case) and everything feels good.

RonR
Posts: 788
Joined: Tue Apr 12, 2016 10:29 pm
Location: US

Re: Extra 16M memory on Pi2/Pi3

Wed Aug 02, 2017 6:26 pm

dom wrote:
Tue Aug 01, 2017 3:23 pm
But with this layout the arm can't see the reloc as it's in the top 16M, so we move it down by 10M, hence the missing 10M you see.
Something still doesn't compute.

With gpu_mem=32:

[email protected]:~# vcgencmd get_mem arm
arm=992M
[email protected]:~# vcgencmd get_mem gpu
gpu=32M

Total=1024

With any value of gpu_mem less than 32, the gpu is only allocated 16M (and 10M disappears from the total).

With gpu_mem=31:

[email protected]:~# vcgencmd get_mem arm
arm=998M
[email protected]:~# vcgencmd get_mem gpu
gpu=16M

Total= 1014

With gpu_mem=34:

[email protected]:~# vcgencmd get_mem arm
arm=990M
[email protected]:~# vcgencmd get_mem gpu
gpu=34M

Total=1024

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rpdom
Posts: 16100
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: Extra 16M memory on Pi2/Pi3

Wed Aug 02, 2017 6:59 pm

As dom said, if you allocate less than 32MB to the GPU, some of it needs to be moved down by 10MB or the ARM cannot access it. The top few MB of the ARM address bus is reserved for peripheral access, while the GPU can use it as RAM.

RonR
Posts: 788
Joined: Tue Apr 12, 2016 10:29 pm
Location: US

Re: Extra 16M memory on Pi2/Pi3

Wed Aug 02, 2017 7:16 pm

From: https://www.raspberrypi.org/documentati ... /memory.md

Memory options in config.txt

gpu_mem

GPU memory in megabytes. This sets the memory split between the CPU and GPU; the CPU gets the remaining memory. Minimum value is 16; maximum value is 192, 448, or 944, depending on whether you are using a 256M, 512MB, or 1024MB Pi. The default value is 64.

======

This apparently needs to be expanded upon to say:

Setting any value from 16 - 31 will result in 16MB of GPU memory being used and 10MB of overall memory being lost.

runboy93
Posts: 352
Joined: Tue Feb 28, 2017 1:17 pm
Location: Finland
Contact: Website

Re: Extra 16M memory on Pi2/Pi3

Wed Aug 02, 2017 8:36 pm

What use you need so less GPU memory? server or similar?

RonR
Posts: 788
Joined: Tue Apr 12, 2016 10:29 pm
Location: US

Re: Extra 16M memory on Pi2/Pi3

Wed Aug 02, 2017 8:57 pm

runboy93 wrote:
Wed Aug 02, 2017 8:36 pm
What use you need so less GPU memory? server or similar?
I run only headless (no video/keyboard/mouse attached) RPi's, accessed only via SSH. No need for any GPU memory.

User avatar
rpdom
Posts: 16100
Joined: Sun May 06, 2012 5:17 am
Location: Chelmsford, Essex, UK

Re: Extra 16M memory on Pi2/Pi3

Thu Aug 03, 2017 5:41 am

RonR wrote:
Wed Aug 02, 2017 8:57 pm
I run only headless (no video/keyboard/mouse attached) RPi's, accessed only via SSH. No need for any GPU memory.
Well, you need at least that 16MB of GPU memory or the Pi won't run at all. The GPU is in charge of the system. But yes, minimal GPU memory is good for headless in most cases (I sometimes do video transcoding on on of my headless Pis using omxtx, so it needs 64MB GPU RAM for that)

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