Details
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Task
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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None
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None
Description
tc_acquire_table and tc_release_table are critical sections of table cache. Among other things, they update TABLE_SHARE::tdc.used_tables:
tc_acquire_table - push new TABLE object to used_tables
tc_release_table - remove TABLE object from used_tables
used_tables list is not really necessary for table cache to operate properly. We can change it with all_tables list instead. tc_acquire_table and tc_release_table wont need to access all_tables list at all.
The cost is as following:
- 2 additional pointers per TABLE object
- SHOW OPEN TABLES will have to iterate all_tables and skip objects with in_use == 0
- same for TABLE_SHARE::visit_subgraph()
- same for kill_delayed_threads_for_table()
A patch for this task has been tested (read-only single table OLTP, 4 CPU linux server) and shown ~30% lower LOCK_open wait time and ~20% higher tps.
Attachments
Issue Links
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- Closed
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- Closed
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MDEV-5864 Reduce usage of LOCK_open: TABLE_SHARE::tdc.free_tables
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- Closed
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- Closed
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- Closed
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- Closed
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Activity
| Description |
tc_acquire_table and tc_release_table are critical sections of table cache. Among other things, they update TABLE_SHARE::tdc.used_tables: tc_acquire_table - push new TABLE object to used_tables tc_release_table - remove TABLE object from used_tables used_tables list is not really necessary for table cache to operate properly. We can change it with all_tables list instead. tc_acquire_table and tc_release_table wont need to access all_tables list at all. The cost is as following: - 2 additional pointers per TABLE object - SHOW OPEN TABLES will have to iterate all_tables and skip objects with in_use == 0 - same for TABLE_SHARE::visit_subgraph A patch for this task has been tested (read-only single table OLTP, 4 CPU linux server) and shown ~30% lower LOCK_open wait time and ~20% higher tps. |
tc_acquire_table and tc_release_table are critical sections of table cache. Among other things, they update TABLE_SHARE::tdc.used_tables: tc_acquire_table - push new TABLE object to used_tables tc_release_table - remove TABLE object from used_tables used_tables list is not really necessary for table cache to operate properly. We can change it with all_tables list instead. tc_acquire_table and tc_release_table wont need to access all_tables list at all. The cost is as following: - 2 additional pointers per TABLE object - SHOW OPEN TABLES will have to iterate all_tables and skip objects with in_use == 0 - same for TABLE_SHARE::visit_subgraph() - same for kill_delayed_threads_for_table() A patch for this task has been tested (read-only single table OLTP, 4 CPU linux server) and shown ~30% lower LOCK_open wait time and ~20% higher tps. |
| Status | Open [ 1 ] | In Progress [ 3 ] |
| Attachment | mdev4956.patch [ 23301 ] |
| Assignee | Sergey Vojtovich [ svoj ] | Sergei Golubchik [ serg ] |
| Assignee | Sergei Golubchik [ serg ] | Sergey Vojtovich [ svoj ] |
| Fix Version/s | 10.0.6 [ 13202 ] | |
| Fix Version/s | 10.0.5 [ 13201 ] |
| Fix Version/s | 10.0.7 [ 14100 ] | |
| Fix Version/s | 10.0.6 [ 13202 ] |
| Assignee | Sergey Vojtovich [ svoj ] | Sergei Golubchik [ serg ] |
Sergei, please review updated patch:
Date: Tue, 10 Dec 2013 15:00:43 +0000 (UTC)
From: Sergey Vojtovich <svoj@mariadb.org>
To: commits@mariadb.org
Subject: [Commits] Rev 3914: MDEV-4956 - Reduce usage of LOCK_open: TABLE_SHARE::tdc.used_tables in lp:maria/10.0
| Status | In Progress [ 3 ] | Stalled [ 10000 ] |
Pushed to 10.0.7, revision-id: svoj@mariadb.org-20131210150036-imkvngj5125mukqu
| Resolution | Fixed [ 1 ] | |
| Status | Stalled [ 10000 ] | Closed [ 6 ] |
| Workflow | defaullt [ 28709 ] | MariaDB v2 [ 43829 ] |
| Workflow | MariaDB v2 [ 43829 ] | MariaDB v3 [ 63029 ] |
| Workflow | MariaDB v3 [ 63029 ] | MariaDB v4 [ 132184 ] |
Sergei, please review attached patch. Committed patch didn't reach mailing list for some reason.