Migrating MySQL server to MariaDb or Percona? I have a MySQL application (MySQL 5.5) running on a virtual Ubuntu 16.04 (64bit) server with 2 kernels and 8 GB RAM. I consists of a few, small RW tables and appr. 30 read-only InnoDb tables with 100-150k rows in each (totaling ~ 1-2 GB data + indexes). Almost all queries gather data from several of the read-only tables (lots of different joins).

Wanting to increase overall performance, should I try to:


switch to MariaDb and Aria tables ?
switch to Percona and XtraDB ?
add more RAM (kernels) ?
or something else ?
The overall performance of MySQL/MariaDB/Percona and InnoDB/XtraDB etc, is minimal.  There are specific cases where one shines over another.  You should not expect a magical improvement.

Instead...  You should look at what is specifically causing trouble and tackle that.

High CPU:  Add composite index / revise query -- but first locate the slowly running query.

High I/O:  Same as high CPU, plus poor Joins, excessively sized datatypes (eg, BIGINT where SMALLINT UNSIGNED would suffice), etc.

Swapping:  This is terrible -- probably caused by carelessly increasing values in my.cnf

Come back with worst query, together with SHOW CREATE TABLE.

Adding RAM won't help -- your dataset is significantly smaller than RAM.  But do check innodb_buffer_pool_size.