MySQL Server 5.6 defaults changes
Posted
by user12626240
on Oracle Blogs
See other posts from Oracle Blogs
or by user12626240
Published on Thu, 4 Oct 2012 16:36:31 +0000
Indexed on
2012/10/04
21:46 UTC
Read the original article
Hit count: 238
/Oracle
We're improving the MySQL Server defaults, as announced by Tomas Ulin at MySQL Connect. Here's what we're changing:
Setting |
Old | New | Notes |
back_log | 50 | 50 + ( max_connections / 5 ) capped at 900 | |
binlog_checksum | off | CRC32 |
New variable in 5.6 |
binlog_row_event_max_size | 1k | 8k | |
flush_time | 1800 | Windows changes from 1800 to 0 |
Was already 0 on other platforms |
host_cache_size | 128 | 128 + 1 for each of the first 500 max_connections + 1 for every 20 max_connections over 500, capped at 2000 |
New variable in 5.6 |
innodb_autoextend_increment | 8 | 64 |
Now affects *.ibd files. 64 is 64 megabytes |
innodb_buffer_pool_instances |
0 | 8. On 32 bit Windows only, if innodb_buffer_pool_size is greater than 1300M, default is innodb_buffer_pool_size / 128M | |
innodb_concurrency_tickets | 500 | 5000 |
|
innodb_file_per_table | off | on |
|
innodb_log_file_size |
5M | 48M |
InnoDB will always change size to match my.cnf value. Also see innodb_log_compressed_pages and binlog_row_image |
innodb_old_blocks_time | 0 | 1000 |
1 second |
innodb_open_files | 300 | 300; if innodb_file_per_table is ON, higher of table_open_cache or 300 | |
innodb_purge_batch_size |
20 | 300 | |
innodb_purge_threads |
0 | 1 | |
innodb_stats_on_metadata | on | off | |
join_buffer_size | 128k | 256k |
|
max_allowed_packet | 1M | 4M |
|
max_connect_errors | 10 | 100 |
|
open_files_limit | 0 | 5000 |
See note 1 |
query_cache_size | 0 | 1M |
|
query_cache_type | on/1 | off/0 |
|
sort_buffer_size | 2M | 256k |
|
sql_mode | none | NO_ENGINE_SUBSTITUTION |
See later post about default my.cnf for STRICT_TRANS_TABLES |
sync_master_info | 0 | 10000 |
Recommend: master_info_repository=table |
sync_relay_log | 0 | 10000 |
|
sync_relay_log_info | 0 | 10000 |
Recommend: relay_log_info_repository=table. Also see Replication Relay and Status Logs |
table_definition_cache | 400 | 400 + table_open_cache / 2, capped at 2000 | |
table_open_cache | 400 | 2000 | Also see table_open_cache_instances |
thread_cache_size |
0 | 8 + max_connections/100, capped at 100 | |
Note 1: In 5.5 there was already a rule to make open_files_limit 10 + max_connections + table_cache_size * 2 if that was higher than the user-specified value. Now uses the higher of that and (5000 or what you specify).
We are also adding a new default my.cnf file and guided instructions on the key settings to adjust. More on this in a later post. We're also providing a page with suggestions for settings to improve backwards compatibility. The old example files like my-huge.cnf are obsolete.
Some of the improvements are present from 5.6.6 and the rest are coming. These are ideas, and until they are in an official GA release, they are subject to change. As part of this work I reviewed every old server setting plus many hundreds of emails of feedback and testing results from inside and outside Oracle's MySQL Support team and the many excellent blog entries and comments from others over the years, including from many MySQL Gurus out there, like Baron, Sheeri, Ronald, Schlomi, Giuseppe and Mark Callaghan.
With these changes we're trying to make it easier to set up the server by adjusting only a few settings that will cause others to be set. This happens only at server startup and only applies to variables where you haven't set a value. You'll see a similar approach used for the Performance Schema. The Gurus don't need this but for many newcomers the defaults will be very useful.
Possibly the most unusual change is the way we vary the setting for innodb_buffer_pool_instances for 32-bit Windows. This is because we've found that DLLs with specified load addresses often fragment the limited four gigabyte 32-bit address space and make it impossible to allocate more than about 1300 megabytes of contiguous address space for the InnoDB buffer pool. The smaller requests for many pools are more likely to succeed.
If you change the value of innodb_log_file_size in my.cnf you will see a message like this in the error log file at the next restart, instead of the old error message:
[Warning] InnoDB: Resizing redo log from 2*64 to 5*128 pages, LSN=5735153
One of the biggest challenges for the defaults is the millions of installations on a huge range of systems, from point of sale terminals and routers though shared hosting or end user systems and on to major servers with lots of CPU cores, hundreds of gigabytes of RAM and terabytes of fast disk space. Our past defaults were for the smaller systems and these change that to larger shared hosting or shared end user systems, still with a bias towards the smaller end. There is a bias in favour of OLTP workloads, so reporting systems may need more changes. Where there is a conflict between the best settings for benchmarks and normal use, we've favoured production, not benchmarks.
We're very interested in your feedback, comments and suggestions.
© Oracle Blogs or respective owner