[MDEV-19391] Create new "Registering transaction" thread state Created: 2019-05-04 Updated: 2020-08-25 Resolved: 2019-08-06 |
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| Status: | Closed |
| Project: | MariaDB Server |
| Component/s: | Locking, Server, Storage Engine - InnoDB, XA |
| Fix Version/s: | N/A |
| Type: | Task | Priority: | Major |
| Reporter: | Geoff Montee (Inactive) | Assignee: | Sergei Golubchik |
| Resolution: | Won't Fix | Votes: | 0 |
| Labels: | None | ||
| Issue Links: |
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| Description |
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Currently, when an InnoDB transaction is in the "System lock" state, it appears that it also performs tasks related to transaction registration, since this is done from ha_innobase::external_lock. Should we create a new thread state called "Registering transaction" or something for this portion of the work? For example, we can see that the server goes into the "System lock" state and asks the storage engine to get the external lock here: https://github.com/MariaDB/server/blob/mariadb-10.4.4/sql/lock.cc#L341 And as part of that process, InnoDB calls innobase_register_trx(): https://github.com/MariaDB/server/blob/mariadb-10.4.4/storage/innobase/handler/ha_innodb.cc#L15651 which calls trans_register_ha() and trx_register_for_2pc(): https://github.com/MariaDB/server/blob/mariadb-10.4.4/storage/innobase/handler/ha_innodb.cc#L2987 https://github.com/MariaDB/server/blob/mariadb-10.4.4/sql/handler.cc#L1176 https://github.com/MariaDB/server/blob/mariadb-10.4.4/storage/innobase/handler/ha_innodb.cc#L2779 |
| Comments |
| Comment by Sergei Golubchik [ 2019-08-06 ] |
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trans_register_ha() and trx_register_for_2pc() are very fast, no locks, just few assignments. |
| Comment by Geoff Montee (Inactive) [ 2019-08-06 ] |
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The reason that I created this task is that I saw threads hanging in this section of code. Since the thread state used in this section of code is "System lock", the user assumed that the hung threads were waiting on some system lock required for the query. I eventually tracked down the root cause to the audit plugin performance issue, https://github.com/MariaDB/server/blob/mariadb-10.3.7/sql/handler.cc#L6125 https://github.com/MariaDB/server/blob/mariadb-10.3.7/sql/sql_audit.h#L285 Since the problem ended up being related to the audit plugin API, maybe adding a new thread state like the one in MDEV-20269 would be better. |