Merge pull request 'Disable busy waits in the default OTP vm.args configuration.' (#693) from erincandescent/akkoma:otp-tune-vm-busywait into develop

Reviewed-on: #693

docs/docs/configuration/optimisation/optimizing_beam.md

@@ -25,11 +25,14 @@ Tuning the BEAM requires you provide a config file normally called [vm.args](htt
 
 `ExecStart=/usr/bin/elixir --erl '-args_file /opt/akkoma/config/vm.args' -S /usr/bin/mix phx.server`
 
+If using an OTP release, set the `RELEASE_VM_ARGS` environment variable to the path to the vm.args file.
+
 Check your OS documentation to adopt a similar strategy on other platforms.
 
 ### Virtual Machine and/or few CPU cores
 
-Disable the busy-waiting. This should generally only be done if you're on a platform that does burst scheduling, like AWS.
+Disable the busy-waiting. This should generally be done if you're on a platform that does burst scheduling, like AWS, or if you're running other
+services on the same machine.
 
 **vm.args:**
 
@@ -39,6 +42,8 @@ Disable the busy-waiting. This should generally only be done if you're on a plat
 +sbwtdio none
 ```
 
+These settings are enabled by default for OTP releases
+
 ### Dedicated Hardware
 
 Enable more busy waiting, increase the internal maximum limit of BEAM processes and ports. You can use this if you run on dedicated hardware, but it is not necessary.

rel/vm.args.eex

@@ -9,3 +9,9 @@
 
 ## Tweak GC to run more often
 ##-env ERL_FULLSWEEP_AFTER 10
+
+## Disable busy waits; vastly reduces CPU usage while idle
+## See https://docs.akkoma.dev/stable/configuration/optimisation/optimizing_beam/#virtual-machine-andor-few-cpu-cores
++sbwt none
++sbwtdcpu none
++sbwtdio none