InnoDB write-only performance regression

Starting with MariaDB 10.2.2 there is a heavy performance regression for write-only workload and low thread counts.

Benchmark: sysbench OLTP with --oltp_simple_ranges=0 --oltp-distinct-ranges=0 --oltp-sum-ranges=0 --oltp-order-ranges=0 --oltp-point-selects=0 --oltp_non_index_updates=9 --oltp_index_updates=9. 32 tables with 10 mio rows total (yields ~2.5GB tablespaces). Datadir residing on RAID-0 on two SSD.

my.cnf

[mysqld]

performance_schema = 0

secure-file-priv = /tmp

max_connections = 600

table_open_cache = 1200

query_cache_type = 0

innodb-file-per-table = true

innodb-flush-method = O_DIRECT

innodb-buffer-pool-size = 16G

innodb_log_file_size = 2G

innodb_log_buffer_size = 8M

innodb_buffer_pool_instances = 8

loose-innodb_adaptive_hash_index_parts = 16

loose-innodb_adaptive_hash_index_partitions = 16

innodb_io_capacity = 5000

loose-innodb_flush_neighbors = 0

innodb_write_io_threads = 8

This issue popped up during work on MDEV-10123 (see there for more numbers). This could be the same issue as MDEV-11937.