bytes are possibly lost
Timer thread of threadpool is created "joinable", but they're not "joined" on
completion. This causes memory leaks around thread local storage.
Fixed by joining timer thread.
An addition to fix for MDEV-5205, fixes server crash on shutdown.
Thread groups are destroyed asynchronously, that is kill server
thread sends shutdown request to all thread groups without waiting
for compeltion.
It means all_groups array must not be freed until all thread groups
are down. This patch suggests that all_groups is freed when last
thread group is destroyed.
Note 1: threadpool code doesn't surround atomic ops with atomic locks,
thus no locks for shutdown_group_count.
Note 2: this patch preserves old behaviour, but we may need to wait
until all thread groups are down before returning from tp_end().
- thread_pool_size command line option upper limit increased to 100 000
(same as for max_connections)
- thread_pool_size system variable upper limit is maximum of 128 or
the value given at command line
- thread groups are now allocated dynamically
Different limit for command line option and system variable was done to
avoid additional mutex for all_groups and threadpool_max_size.
Assertion happens in replication thread during THD destruction, when thread calls my_sync(), which in turn calls thd_wait_begin() callback. Connection count can be 0, because the counter was decremented before THD destructor.
This assertion currently reproducible only in Percona server and not in MariaDB, due to differences in replication code.
Fixed by moving code to decrement connection counter after the THD destructor.
Use post_kill_notification in for one_thread_per_connection scheduler,
the same as already used in threadpool, to reliably wake a thread stuck in
read() or in different poll() variations.
To allow it, change minimum of thread_pool_stall_limit to be 10 milliseconds.
Also introduce a new parameter to oversubscribe a group . Number of threads running in parallel would be higher than it normally should, leading to thrashing, but it may improving preemptiveness, which is useful for the described corner case.
