Re: Unexpected RAM usage on MySQL
Posted by: Peter Brawley
Date: March 18, 2019 11:22AM

MySQL crashed out of mem when RAM use reached ~14GB and swap use reached ~27GB, though calculated max mem use is less than half that.

Main suspects seem to be too many unoptimised queries, 33k open files and too many created tmp tables going to disk. Re the latter, grow tmp_table_size, grow max_heap_size, diminish use of blobs, optimise queries, use db.table syntax to avoid db changes, use Heap tables in queries.

> app services are set to a nightly restart exactly to try to reclaim some memory ...

Okeh but the first sample was just 3h and perhaos wasn't peak time, could you do 12h including the busiest part of the day?

We're still missing something big. Could you run free -m and top say every 30 min from startup to see how and when usage max's out?

And a no-cost experiment, please run ...


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