GadgetAngel
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pi 4B not showing Video on HDMI0 if memory split set to 896MB

Sun Aug 04, 2019 7:36 pm

Hi,

I downloaded the latest Buster with desktop and placed it on my 32GB SD card, placed it into my raspberry pi 4B and booted the system.

The desktop showed up and I went through the initial setup

I did the following:

sudo apt-get update
sudo apt-get dist-upgrade

reboot

Once I was back, I changed the memory split in my 4GB raspberry pi 4B to 896MB for the GPU

Now, when I had to reboot to set this memory split, my raspberry pi will no longer show the desktop on the HDMI screen I have hooked up.

I only changed the memory split since the previous boot.

With a 4GB raspberry pi , I would not think that setting the GPU to 1024MB would be inconceivable. I want to use the device as a rtsp server for my home security cameras.

I read the section on raspberry pi boot, and no video showing but nothing there fits becauce my ACT ligh is blinking in a random way. I checked to see if the raspberry pi 4B EEPROM was OK and it is. If I pull out everything from off the 4B and boot with out the SD card the 4B detects the SD card is missing.

Any help on this would be appreciated

jamesh
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Sun Aug 04, 2019 8:51 pm

896MB is a crazy number - 128 should be more than enough for most things. I'm assuming this is gpu_mem btw.

So edit the card in another device, change gpu_mem to something sane, and it should spring in to life.
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GadgetAngel
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Sun Aug 04, 2019 9:22 pm

With a raspberry pi 3B+ I can have a maximum GPU memory of 256MB out of 1024MB. That is a 256MB is one quarter of my total memory available or 25%.

Since I bought a 4GB raspberry pi 4B, then I should be able to set the GPU to 1024MB with out an issue. But for some unknown reason the OS will not show the video screen properly.

BTW, 896MB as the default set by the OS. I tried to set the memory split at 1024MB and the OS changed the amount to 896. That is not the number I put in!!!

If this device, is suppose to act as desktop unit. Then asking the OS to allocate 25% of its memory so the GPU can also do some processing is NOT asking too much. In my humble opinion asking raspberry.org to set the boot image to accommodate this is not asking too much. I would like to use the GPU to do some video processing and using 25% of my total memory to do that is a reasonable request, and this MUST be fixed!!

So can someone please report this as bug to the appropriate people.

BTW, I changed my /boot/config.txt file to run the screen at DMT mode 35. I changed the config.txt file rebooted with memory split at 512MB and the pi booted normally. Now, I went back in to change the memory split to 896MB and rebooted and again the Video screen does not show up and the light on my USB port hub is off. Their is something going on with the pi, memory allocation assignments when the memory split goes above 512MB

Note: the raspberry pi when I have GPU memory split set to 896MB, imy USB hub port {my USB 2.0 hub is self powered and when the USB port is in use the light on the port comes on, usuallly} light also goes out ???? [indicating the USB port is NOT active]

So I go back into the raspberry pi via SSH (yes, the pi is booted even with the memory split at 896MB but I can not access the desktop via the attached monitor) and change the memory split back to 512MB and reboot, the pi will now show the desktop on the attached monitor
Last edited by GadgetAngel on Sun Aug 04, 2019 9:27 pm, edited 1 time in total.

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rpdom
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Sun Aug 04, 2019 9:26 pm

I think you do not understand how the GPU works on the Pi. There is no reason to give it that amount of memory and it will not use it anyway.

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PeterO
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Sun Aug 04, 2019 9:26 pm

GadgetAngel wrote:
Sun Aug 04, 2019 9:22 pm
With a raspberry pi 3B+ I can have a maximum GPU memory of 256MB out of 1024MB. That is a 256MB is one quarter of my total memory available or 25%.

Since I bought a 4GB raspberry pi 4B, then I should be able to set the GPU to 1024MB with out an issue. But for some unknown reason the OS will not show the video screen properly.
Non sequitur I'm afraid.
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Sun Aug 04, 2019 9:37 pm

GadgetAngel wrote:
Sun Aug 04, 2019 9:22 pm
...
I would like to use the GPU to do some video processing and using 25% of my total memory to do that is a reasonable request, and this MUST be fixed!!
Really? Who died and made you king?

The Raspberry Pi foundation does not cater to your personal needs. Their primary goal is promoting computer education, and I seriously doubt you can find any compelling reason educators would need such high GPU memory, so I predict your demands will not be met.

If you want to try and report it as a bugt, go right ahead. No one here is going to do it for you (especially considering the tone of your post, which will not win you any friends here).
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GadgetAngel
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Sun Aug 04, 2019 9:42 pm

I am doing video processing: live video streams into rtsp streams for my home network and I would like the GPU hardware acceleration to be used. This is why I want to use 1024 MB out of 4096MB on my machine.

I bought the 4GB version of this pi 4B to do this. I also want the gigabit Ethernet adapter so I could display all my surveillance cameras on my large screen using github project displaycameras. This turns the raspberry pi into a rtsp server to do the job. With the raspberry pi 3B+ we set the GPU split at 256MB when the 3B+ only has 1024MB of total memory. When I only had two cameras that worked fine but now I have 4 cameras and I want to display them all at the same time. Splitting up my screen into 4 equal parts. Showing each camera at 10 fps. It should be able to handle it with the raspberry pi 4B with 4GB of memory.

But I will not be able to determine this until they can fix this issue with the memory split. I will try using the pi set at 512MB but its the principle of the thing. If I can use 25% of my memory on a raspberry pi 3B+, then I should be allowed to use 25% of my memory for the raspberry pi 4B, especially since it is a better processor, memory access speed has increased, USB speed has increase and Ethernet speed has increase over what the raspberry pi 3B+ can do.

It would be nice to use the device the way it was meant to be used.

GadgetAngel
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Sun Aug 04, 2019 9:44 pm

Never meant for my tone to be bad. If you read and hear that I do apologize.


Please excuse me. Accept my apology.

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PeterO
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Sun Aug 04, 2019 9:46 pm

GadgetAngel wrote:
Sun Aug 04, 2019 9:42 pm
It would be nice to use the device the WAY I'M DEMANDING TO USE IT.
Fixed it for you :lol:
PeterO
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Sun Aug 04, 2019 10:31 pm

GadgetAngel wrote:
Sun Aug 04, 2019 9:42 pm
If I can use 25% of my memory on a raspberry pi 3B+, then I should be allowed to use 25% of my memory for the raspberry pi 4B
There are technical reasons for it not working. It isn't an arbitrary limit to spite you. The GPU can only access the first 1GB of RAM but there are other parts like the ARM cores that also want part of that first 1GB of RAM so you can't just give it all to the GPU. Even 512MB is overkill as it won't use that much.

Throwing more memory at the GPU doesn't help with video encoding anyway because your bottleneck is trying to push all of your concurrent streams through a single video encoder unit inside the SoC. If it runs then it has enough RAM and giving it more will do nothing.

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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Mon Aug 05, 2019 9:07 am

As above - there is absolutely no need for anything above 256MB. The GPU won't use it. You are completely misunderstanding how the memory is used by the GPU. The encoder needs a certain amount of memory to work, and 256 is more than enough for all use cases. The encoder can handle a certain number of giga-pixels per second, and that is fixed, irrespective of the amount of memory allocated to the GPU.
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Mon Aug 12, 2019 12:37 am

I guess part of what is confusing a lot of us is that the documentation is saying one thing and you are saying something else. The board will boot at 768 but not 944(or whatever the max is listed in the documentation or 896). While I have seen no improvement of 768 over 512, things did seem MUCH happier going from 256 to 512. I do run multiple workspaces(not multiple monitors).

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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Mon Aug 12, 2019 8:37 am

Brad Q wrote:
Mon Aug 12, 2019 12:37 am
I guess part of what is confusing a lot of us is that the documentation is saying one thing and you are saying something else. The board will boot at 768 but not 944(or whatever the max is listed in the documentation or 896). While I have seen no improvement of 768 over 512, things did seem MUCH happier going from 256 to 512. I do run multiple workspaces(not multiple monitors).
If you can point me to the erroneous docs I'll update them.

I would not expect to see any performance improvement going from 256 to 512 when using a normal desktop. In fact with the VC4 Mesa driver now the default on the Pi4, and perfectly usable on earlier models, that number should be getting lower, much lower, as the 3D no longer uses the GPU allocated memory.

If using Mesa, and not using the camera or H264 codecs, 64MB would probably be more than enough.
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Tue Aug 13, 2019 12:58 am

"GPU memory in megabytes, sets the memory split between the CPU and GPU; the CPU gets the remaining memory. The minimum value is 16; the maximum value is 192, 448, or 944, depending on whether you are using a 256MB, 512MB, or 1024MB Pi. The default value is 64. For the Raspberry Pi 4, which is available in 1GB, 2GB and 4GB versions, the minimum and maximum value are the same as for a 1GB device."


from :

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


As was stated above, my Pi4-4gb will not boot at 944 or 896, but boots OK at 768. I did not try anything between 768 and 896. While I am new to Pi/Raspbian I have been straight Linux since Fedora Core 4 (FC4) and have been running Centos since Fedora 9(7-9 were not a joy). There have often been things that theoretically should not make a difference but in the real world they do. In my case switching from 256 to 512 made things happier. Snappier changes between workspaces(4). 512 to 768 I saw no difference.

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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Tue Aug 13, 2019 6:40 am

Brad Q wrote:
Tue Aug 13, 2019 12:58 am
"GPU memory in megabytes, sets the memory split between the CPU and GPU; the CPU gets the remaining memory. The minimum value is 16; the maximum value is 192, 448, or 944, depending on whether you are using a 256MB, 512MB, or 1024MB Pi. The default value is 64. For the Raspberry Pi 4, which is available in 1GB, 2GB and 4GB versions, the minimum and maximum value are the same as for a 1GB device."


from :

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


As was stated above, my Pi4-4gb will not boot at 944 or 896, but boots OK at 768. I did not try anything between 768 and 896. While I am new to Pi/Raspbian I have been straight Linux since Fedora Core 4 (FC4) and have been running Centos since Fedora 9(7-9 were not a joy). There have often been things that theoretically should not make a difference but in the real world they do. In my case switching from 256 to 512 made things happier. Snappier changes between workspaces(4). 512 to 768 I saw no difference.
I can think of no technical reasons why going over 256 will make workspace changes faster. All that does is actually take memory away from the 3d system.
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Tue Aug 13, 2019 7:06 am

I have zero (0) idea why or any real understanding of what is going on under the hood. You asked for where the documentation conflicted with what you were saying and I provided it.

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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Tue Aug 13, 2019 7:47 am

On Pi4 GPU memory now just refers to memory that must addressable to the VPU, HVS, Legacy codecs, and camera. So essentially, it's anything that's part of the HVS composition scene or decoder reference frames. For all practical purposes this memory must be within the bottom 1GB of physical memory.

However, on Pi4 V3D now has it's own MMU so textures and other GL resources are not allocated from "GPU memory" and are allocated from Linux system memory.

Therefore, allocating lots of "GPU memory" is normally a waste of memory and will hurt system performance. 128MB is probably plenty for dual 4K HDMI + camera + h.264 decode. There might be some corner cases for large decoder pools etc

There are (low priority) plans to completely get rid of GPU memory and just give the firmware a small block of memory for internal usage with frame-buffers etc just being allocated from CMA, although we'd need to find a way to make them cacheable from the ARM for performance.

btw: The bootloader doesn't actually allocate GPU memory, it just passes the parameter via the fixups to the start.elf file. There's no guarantee that anything > 512MB will work and is completely untested.

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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Tue Aug 13, 2019 8:05 am

The total memory available does seem to track with the amount allotted to the gpu, as long as the amount is bootable.

The 512 vs 512 plus thing tracks with what I am seeing. 512 better, greater than 512 no noticeable difference.

Is there any limitation on ethernet tied to the first 1gb of memory? My particular pi4-4g runs warmer than what most are reporting. Typically 50-60c with three ff windows open(but not active, forums) and thunderbird in a flirc case with 75f room temperature. The case is very warm(not hot enough to burn), so there is good cpu to heat sink contact. When the cpu temp is over 58(ish) youtube crashes all the time, below that it is better. Other web based things follow suit. Chrome youtube is better (not a fan) but even it seems to have issues when over 58. Could the heat be affecting the traces or the memory chip? Running sysbench with all four cores (cpu usage 100%) for ten minutes never gets above 65c. Cables, switch ports, have all been switched out and other machines on same router(asus) are fine.

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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Tue Aug 13, 2019 8:17 am

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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Tue Aug 13, 2019 9:33 am

I am not familiar with the way that edit system is setup but if I am reading it correctly it is still not right. My pi4 will not boot with the gpu_mem set to 944 or 896. So assuming that the prior versions would, there needs to be some note on there about that. While I have not tried anything between 768 and 896, it will boot at 768 but not 896. The allowed values are obviously not the same between the different versions. I would be interesting to know what is actually determining what the real world limitation is. Not the theoretical limitation.

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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Tue Aug 13, 2019 12:50 pm

We've probably never tested with those sorts of number because they are totally unnecessary. 128-256 is the max you should need., and you can get away with 16 or 32 depending on use case. I doubt we will investigate why it goes wrong, simply because is so far out of what is sensible to use.
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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Tue Aug 13, 2019 2:50 pm

jamesh wrote:
Tue Aug 13, 2019 12:50 pm
We've probably never tested with those sorts of number because they are totally unnecessary. 128-256 is the max you should need., and you can get away with 16 or 32 depending on use case. I doubt we will investigate why it goes wrong, simply because is so far out of what is sensible to use.
Timg236 said above that gpu_mem > 512 has never been tested, yet the docs say you can use up to 944. The docs should be updated to specify 512 as the max, I would suggest.

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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Tue Aug 13, 2019 3:46 pm

andrum99 wrote:
Tue Aug 13, 2019 2:50 pm
jamesh wrote:
Tue Aug 13, 2019 12:50 pm
We've probably never tested with those sorts of number because they are totally unnecessary. 128-256 is the max you should need., and you can get away with 16 or 32 depending on use case. I doubt we will investigate why it goes wrong, simply because is so far out of what is sensible to use.
Timg236 said above that gpu_mem > 512 has never been tested, yet the docs say you can use up to 944. The docs should be updated to specify 512 as the max, I would suggest.
I've filed PR #1243: https://github.com/raspberrypi/documentation/pull/1243 to change the docs.

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Re: pi 4B not showing Video on HDMI0 if memory split set to 896MB

Tue Aug 13, 2019 6:42 pm

Just because things don't work with Buster doesn't mean other bare metal OSes won't work.

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