You need to know how much RAM is available to MySQL. See the link I provided for alternatives to Top if desired.
As a preliminary estimate of how much RAM your MySQL installation may need, run this in MySQL...
select engine,data,indexes,total
from (
select
ifnull(engine,'TOTALS') as engine,
concat(data,' GB') as data,
concat(indexes,' GB') as indexes,
concat(tot,' GB') as total,
if(engine is null,-1,tot) as ord
from (
select
engine,
round( sum(data_length)/1024/1024/1024, 2 ) as data,
round( sum(index_length)/1024/1024/1024, 2 ) as indexes,
round( sum(data_length+index_length)/1024/1024/1024, 2 ) as tot
from information_schema.tables
where engine is not null and engine not in('information_schema','performance_schema')
group by engine with rollup
) sums
) list
order by list.ord desc;