Comment 5 for bug 1690399

I see. Back to original issue, the mapping between LRU managers and buffer pool instances is 1:1 by design, and the only way to reduce the LRU manager number is to reduce the buffer pool instance count.

Then, mistuned LRU flushing could manifest in different ways, the more serious one is the lack of free pages. That is seen in PMP as stacktraces involving buf_LRU_get_free_block, and your PMP does not show it. Another would be too-aggressive LRU flushing, but does not seem likely either here (it is capped by innodb_lru_scan_depth for each ~11GB bp instance, which does not seem excessively high).

Thus, I don't see immediate evidence that your performance drop is directly related to LRU flushing yet. Perhaps you can provide further details about the drop itself?