Bug #82577 let variables in my.cnf specify percent of ram
Submitted: 14 Aug 2016 11:43 Modified: 15 Aug 2016 5:58
Reporter: Rick James Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL Server: Options Severity:S3 (Non-critical)
Version: OS:Any
Assigned to: CPU Architecture:Any
Tags: my.cnf, tuning, variables

[14 Aug 2016 11:43] Rick James 
Description:
The most important tunable, innodb_buffer_pool_size, is hard to default reasonably.  If too low, MySQL is inefficient; if too high, it could lead to swapping, which is even less efficient.

Suggest having a syntax like this:
innodb_buffer_pool_size = 70%
where the number refers to a percentage of RAM.  (That value is pretty good for a "dedicated server".)

This number should allow decimals, since some settings need values near 1%:
tmp_table_size = 1%
max_heap_table_size = 1%
join_buffer_size = 1%
sort_buffer_size = 1%
innodb_log_buffer_size = 0.7%
max_allowed_packet = 1.5%

How to repeat:
N/A

Suggested fix:
Code in parsing of config file
[15 Aug 2016 5:58] MySQL Verification Team 
Hello Rick James,

Thank you for the report and feedback!

Thanks,
Umesh