| Bug #61239 | InnoDB silently switches to 1 buffer pool instance if size is < 1GB | ||
|---|---|---|---|
| Submitted: | 20 May 2011 5:01 | Modified: | 10 Apr 2013 15:26 |
| Reporter: | Vasil Dimov | Email Updates: | |
| Status: | Closed | Impact on me: | |
| Category: | MySQL Server: InnoDB storage engine | Severity: | S3 (Non-critical) |
| Version: | 5.6 | OS: | Any |
| Assigned to: | Vasil Dimov | CPU Architecture: | Any |
[10 Apr 2013 15:25]
Bugs System
Added a changelog entry for 5.7.1: Without warning, InnoDB would silently set "innodb-buffer-pool-instances" to 1 if the buffer pool size is less than 1GB. For example, if "innodb-buffer-pool-size" is set to 200M and "innodb-buffer-pool-instances" is set to 4, InnoDB would silently set "innodb-buffer-pool-instances" to 1. This fix implements a warning message and new logic for "innodb-buffer-pool-size" and "innodb-buffer-pool-instances".
Description: For example with these settings: innodb-buffer-pool-size=200M innodb-buffer-pool-instances=4 InnoDB silently switches to using 1 buffer pool instance. Two things should be fixed: 1. A notice should be emitted to the user so he knows that his choice has been overriden. 2. The value of innodb_buffer_pool_instances should be set back to 1, it currently shows 4, which is very confusing. The code that sets back to 1 buffer pool is srv0start.c: 1257 /* Set the maximum number of threads which can wait for a semaphore 1258 inside InnoDB: this is the 'sync wait array' size, as well as the 1259 maximum number of threads that can wait in the 'srv_conc array' for 1260 their time to enter InnoDB. */ 1261 1262 if (srv_buf_pool_size >= 1000 * 1024 * 1024) { 1263 /* If buffer pool is less than 1000 MB, 1264 assume fewer threads. Also use only one 1265 buffer pool instance */ 1266 srv_max_n_threads = 50000; 1267 1268 } else if (srv_buf_pool_size >= 8 * 1024 * 1024) { 1269 1270 srv_buf_pool_instances = 1; 1271 srv_max_n_threads = 10000; 1272 } else { 1273 srv_buf_pool_instances = 1; 1274 srv_max_n_threads = 1000; /* saves several MB of memory, 1275 especially in 64-bit 1276 computers */ 1277 } How to repeat: see above