Improved NUMA
support¶
In cases where the buffer pool memory allocation was bigger than size of the node, system would start swapping already allocated memory even if there is available memory on other node. This is would happen if the default NUMA memory allocation policy was selected. In that case system would favor one node more than other which caused the node to run out of memory. Changing the allocation policy to interleaving, memory will be allocated in round-robin fashion over the available node. This can be done by using the mysqld_safe numa_interleave
option. NOTE: In order for this feature to work correctly mysqld_safe
needs to be started as root
.
Another improvement implemented is preallocating the pages in the buffer pool on startup with innodb_buffer_pool_populate
variable. This forces NUMA
allocation decisions to be made immediately while the buffer cache is clean.
It is generally recommended to enable all of the options together to maximize the performance effects on the NUMA
architecture.
Version Specific Information¶
5.5.28-29.1
- Improved
NUMA
support implemented. This feature was ported from Twitter’s MySQL patches.
System Variables¶
-
variable
innodb_buffer_pool_populate
¶ Command Line: Yes Config File: Yes Location: mysqld Scope: Global Dynamic: No Variable Type: Boolean Default Value: 0 Range: 0/1
When this variable is enabled, InnoDB preallocates pages in the buffer pool on startup to force NUMA
allocation decisions to be made immediately while the buffer cache is clean.
Command-line Options for mysqld_safe¶
-
variable
flush_caches
¶ Command Line: Yes Config File: Yes Location: mysqld_safe Dynamic: No Variable Type: Boolean Default Value: 0 Range: 0/1
When enabled this will flush and purge buffers/caches before starting the server to help ensure NUMA
allocation fairness across nodes. This option is useful for establishing a consistent and predictable behavior for normal usage and/or benchmarking.
-
variable
numa_interleave
¶ Command Line: Yes Config File: Yes Location: mysqld_safe Dynamic: No Variable Type: Boolean Default Value: 0 Range: 0/1
When this option is enabled, mysqld will run with its memory interleaved on all NUMA
nodes by starting it with numactl --interleave=all
. In case there is just 1 CPU/node, allocations will be “interleaved” between that node.
Contact Us
For free technical help, visit the Percona Community Forum.To report bugs or submit feature requests, open a JIRA ticket.
For paid support and managed or professional services, contact Percona Sales.