(Inadequate background LRU flushing for write workloads with InnoDB compression).
If InnoDB compression is used and the workload has writes, the
following situation is possible. The LRU flusher issues an LRU flush
request for an instance. buf_do_LRU_batch decides to perform
unzip_LRU eviction and this eviction might fully satisfy the
request. Then buf_flush_LRU_tail checks the number of flushed pages in
the last iteration, finds it to be zero, and wrongly decides not to
flush that instance anymore.
Fixed by maintaining unzip_LRU eviction counter in struct
flush_counter_t variables, and checking it in buf_flush_LRU_tail when
deciding whether to stop flushing the current instance.
Added test cases for new configuration files to get mysql-test-run suite sys_vars
to pass. Fix some small errors.
