Fix shm size calculation (#5123)

* Fix shm size calculation

* Improve shm examples

* Add note about default shm size for add-ons

* adjust language

Co-authored-by: Blake Blackshear <blakeb@blakeshome.com>
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Felipe Santos 2023-01-18 10:46:57 -03:00 committed by GitHub
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### Calculating required shm-size
Frigate utilizes shared memory to store frames during processing. The default `shm-size` provided by Docker is 64m.
Frigate utilizes shared memory to store frames during processing. The default `shm-size` provided by Docker is **64MB**.
The default shm-size of 64m is fine for setups with 2 or less 1080p cameras. If Frigate is exiting with "Bus error" messages, it is likely because you have too many high resolution cameras and you need to specify a higher shm size.
The default shm size of **64MB** is fine for setups with **2 cameras** detecting at **720p**. If Frigate is exiting with "Bus error" messages, it is likely because you have too many high resolution cameras and you need to specify a higher shm size.
You can calculate the necessary shm-size for each camera with the following formula using the resolution specified for detect:
The Frigate container also stores logs in shm, which can take up to **30MB**, so make sure to take this into account in your math as well.
```
(width * height * 1.5 * 9 + 270480)/1048576 = <shm size in mb>
You can calculate the necessary shm size for each camera with the following formula using the resolution specified for detect:
```console
# Replace <width> and <height>
$ python -c 'print("{:.2f}MB".format((<width> * <height> * 1.5 * 9 + 270480) / 1048576))'
# Example for 1280x720
$ python -c 'print("{:.2f}MB".format((1280 * 720 * 1.5 * 9 + 270480) / 1048576))'
12.12MB
# Example for eight cameras detecting at 1280x720, including logs
$ python -c 'print("{:.2f}MB".format(((1280 * 720 * 1.5 * 9 + 270480) / 1048576) * 8 + 30))'
126.99MB
```
The shm size cannot be set per container for Home Assistant Addons. You must set `default-shm-size` in `/etc/docker/daemon.json` to increase the default shm size. This will increase the shm size for all of your docker containers. This may or may not cause issues with your setup. https://docs.docker.com/engine/reference/commandline/dockerd/#daemon-configuration-file
The shm size cannot be set per container for Home Assistant add-ons. However, this is probably not required since by default Home Assistant Supervisor allocates `/dev/shm` with half the size of your total memory. If your machine has 8GB of memory, chances are that Frigate will have access to up to 4GB without any additional configuration.
### Raspberry Pi 3/4