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Re: Bad performance on MySQL 8.0 compared to 5.7
Posted by: Peter Brawley
Date: August 16, 2022 10:04AM

8.0 does more, so it needs more resources than 5.7, so I'd need to see the results, in each MySQL instance, of ...

show global status;

select * from sys.memory_global_total;

  substring_index(event_name,'/',2) as code_area, 
  sys.format_bytes( sum(current_alloc) ) as current_alloc 
from sys.x$memory_global_by_current_bytes 
group by substring_index(event_name,'/',2) 
order by sum(current_alloc) desc;

select concat(format(a.num * 100.0 / b.num,2),"%") bufferpoolfullpct 
  (select variable_value num from performance_schema.global_status
  where variable_name = 'innodb_buffer_pool_pages_data') a,
  (select variable_value num from performance_schema.global_status
  where variable_name = 'innodb_buffer_pool_pages_total') b;

And please post the results of running this query in one of the MySQL instances ...

select engine,data,indexes,total
from (
    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 (
      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;

Edited 1 time(s). Last edit at 08/16/2022 10:04AM by Peter Brawley.

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Re: Bad performance on MySQL 8.0 compared to 5.7
August 16, 2022 10:04AM

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