Bug #114604 innodb_dedicated_server: need an option to lower the 'detected server memory'
Submitted: 10 Apr 5:15
Reporter: Shane Bester (Platinum Quality Contributor) Email Updates:
Status: Verified Impact on me:
Category:MySQL Server: InnoDB storage engine Severity:S4 (Feature request)
Version:8.0.36 OS:Any
Assigned to: CPU Architecture:Any

[10 Apr 5:15] Shane Bester
With reference to:

On small servers (e.g. < 64G RAM), using 75% of detected server memory for innodb_buffer_pool_size ends up starving the OS and even backup software.

We require another option,  such as :

innodb_dedicated_server_reserve=8G   so this can exclude 8G as a fixed amount,
from the calculation and leave that as the base amount to use for OS and other mysql buffers (GR, optimizer, routine + table cache, etc).

e.g. on a 16G server:

current: 16 * 0.75 = 12G used for innodb_buffer_pool_size is too much.
proposed: (16 - innodb_dedicated_server_reserve) * 0.75 = 6G is more appropriate for some.

How to repeat:
Run load test on GR with innodb_dedicated_server=ON on a 16G server, server will run out of memory pretty fast.

Reason is innodb_dedicated_server doesn't take into account anything else using RAM within the server itself.  So it's overly confident.

Suggested fix:
revise the algorithm use in establishing how much of the detected RAM is safe to use.

On massive servers 75% is okay, because 25% left for the OS + other mysql internals is enough.   On small servers < 64G it gets to be a tight fit.