Re: Bad performance on MySQL 8.0 compared to 5.7

[Raphael Yeung]

Thank you Peter for your advices.

First, I had checked on the privileges. It should be able to access sys.memory_global_total. But I always get it null and no idea for that after Googled for several hours...

Then for the innodb_buffer_pool_size, I had changed both server to 6GB (while 8GB is available in the servers).
With reference to the provided links, tried to added "transaction_write_set_extraction=OFF" to my mysql.
And tried to use sysbench to have the performance checking again. I still have the similar result that 8.0 performs worse than 5.7.

I hope you can give some more advices if possible.
Thank you.

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[8.0]
SQL statistics:
queries performed:
read: 10091088
write: 2883168
other: 1441584
total: 14415840
transactions: 720792 (400.42 per sec.)
queries: 14415840 (8008.42 per sec.)
ignored errors: 0 (0.00 per sec.)
reconnects: 0 (0.00 per sec.)

General statistics:
total time: 1800.0842s
total number of events: 720792

Latency (ms):
min: 3.37
avg: 59.93
max: 315.52
95th percentile: 89.16
sum: 43198587.77

Threads fairness:
events (avg/stddev): 30033.0000/190.90
execution time (avg/stddev): 1799.9412/0.02

[5.7]
SQL statistics:
queries performed:
read: 12249314
write: 3499804
other: 1749902
total: 17499020
transactions: 874951 (486.06 per sec.)
queries: 17499020 (9721.28 per sec.)
ignored errors: 0 (0.00 per sec.)
reconnects: 0 (0.00 per sec.)

General statistics:
total time: 1800.0715s
total number of events: 874951

Latency (ms):
min: 1.89
avg: 49.37
max: 1594.87
95th percentile: 101.13
sum: 43198008.80

Threads fairness:
events (avg/stddev): 36456.2917/256.62
execution time (avg/stddev): 1799.9170/0.02