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MDEV-33668: Refactor parallel replication round-robin scheduling to use explicit FIFO

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This is a preparatory patch to facilitate the next commit to improve
the scheduling of XA transactions in parallel replication.

When choosing the scheduling bucket for the next event group in
rpl_parallel_entry::choose_thread(), use an explicit FIFO for the
round-robin selection instead of a simple cyclic counter i := (i+1) % N.

This allows to schedule XA COMMIT/ROLLBACK dependencies explicitly without
changing the round-robin scheduling of other event groups.

Reviewed-by: Andrei Elkin <andrei.elkin@mariadb.com>
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>
This commit is contained in:
Kristian Nielsen
2024-02-27 12:19:18 +01:00
committed by Andrei
parent 89c907bd4f
commit f9ecaa87ce
2 changed files with 42 additions and 25 deletions
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13
sql/rpl_parallel.h
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@@ -326,6 +326,11 @@ struct rpl_parallel_thread_pool {
struct rpl_parallel_entry {
struct sched_bucket : public ilink {
sched_bucket() : thr(nullptr) { }
rpl_parallel_thread *thr;
};
mysql_mutex_t LOCK_parallel_entry;
mysql_cond_t COND_parallel_entry;
uint32 domain_id;
@@ -355,17 +360,19 @@ struct rpl_parallel_entry {
uint64 stop_sub_id;
/*
Cyclic array recording the last rpl_thread_max worker threads that we
Array recording the last rpl_thread_max worker threads that we
queued event for. This is used to limit how many workers a single domain
can occupy (--slave-domain-parallel-threads).
The array is structured as a FIFO using an I_List thread_sched_fifo.
Note that workers are never explicitly deleted from the array. Instead,
we need to check (under LOCK_rpl_thread) that the thread still belongs
to us before re-using (rpl_thread::current_owner).
*/
rpl_parallel_thread **rpl_threads;
sched_bucket *rpl_threads;
I_List<sched_bucket> *thread_sched_fifo;
uint32 rpl_thread_max;
uint32 rpl_thread_idx;
/*
The sub_id of the last transaction to commit within this domain_id.
Must be accessed under LOCK_parallel_entry protection.