Optimizing InnoDB Configuration Variables

Different settings work best for servers with light, predictable loads, versus servers that are running near full capacity all the time, or that experience spikes of high activity.

Because the InnoDB storage engine performs many of its optimizations automatically, many performance-tuning tasks involve monitoring to ensure that the database is performing well, and changing configuration options when performance drops. See , "Integration with MariaDB PERFORMANCE_SCHEMA" for information about detailed InnoDB performance monitoring.

For information about the most important and most recent InnoDB performance features, see , "InnoDB Performance and Scalability Enhancements". Even if you have used InnoDB tables in prior versions, these features might be new to you, because they are from the "InnoDB Plugin". The Plugin co-existed alongside the built-in InnoDB in MariaDB 5.1, and becomes the default storage engine in MariaDB 5.5 and higher.

The main configuration steps you can perform include:

• Enabling InnoDB to use high-performance memory allocators on systems that include them. See , "Using Operating System Memory Allocators".
• Controlling the types of DML operations for which InnoDB buffers the changed data, to avoid frequent small disk writes. See , "Controlling InnoDB Change Buffering". Because the default is to buffer all types of DML operations, only change this setting if you need to reduce the amount of buffering.
• Turning the adaptive hash indexing feature on and off. See , "Controlling Adaptive Hash Indexing". You might change this setting during periods of unusual activity, then restore it to its original setting.
• Setting a limit on the number of concurrent threads that InnoDB processes, if context switching is a bottleneck. See , "Changes Regarding Thread Concurrency".
• Controlling the amount of prefetching that InnoDB does with its read-ahead operations. When the system has unused I/O capacity, more read-ahead can improve the performance of queries. Too much read-ahead can cause periodic drops in performance on a heavily loaded system. See , "Changes in the Read-Ahead Algorithm".
• Increasing the number of background threads for read or write operations, if you have a high-end I/O subsystem that is not fully utilized by the default values. See , "Multiple Background InnoDB I/O Threads".
• Controlling how much I/O InnoDB performs in the background. See , "Controlling the InnoDB Master Thread I/O Rate". The amount of background I/O is higher than in MariaDB 5.1, so you might scale back this setting if you observe periodic drops in performance.
• Controlling the algorithm that determines when InnoDB performs certain types of background writes. See , "Controlling the Flushing Rate of Dirty Pages from the InnoDB Buffer Pool". The algorithm works for some types of workloads but not others, so might turn off this setting if you observe periodic drops in performance.
• Taking advantage of multicore processors and their cache memory configuration, to minimize delays in context switching. See , "Control of Spin Lock Polling".
• Preventing one-time operations such as table scans from interfering with the frequently accessed data stored in the InnoDB buffer cache. See , "Making Buffer Pool Scan Resistant".
• Adjusting your log files to a size that makes sense for reliability and crash recovery. See , "Improvements to Crash Recovery Performance". Historically, people have kept their InnoDB log files small to avoid long startup times after a crash. Internal improvements in InnoDB make startup much faster, so the log file size is not such a performance factor anymore. If your log files are artificially small, increasing the size can help performance by reducing the I/O that occurs as redo log records are recycled.
• Configuring the size and number of instances for the InnoDB buffer pool, especially important for systems with multi-gigabyte buffer pools. See , "Improvements to Performance from Multiple Buffer Pools".
• Increasing the maximum number of concurrent transactions, which dramatically improves scalability for the busiest databases. See , "Better Scalability with Multiple Rollback Segments". Although this feature does not require any action during day-to-day operation, you must perform a slow shutdown during or after upgrading the database to MariaDB 5.5 to enable the higher limit.
• Moving purge operations (a type of garbage collection) into a background thread. See , "Better Scalability with Improved Purge Scheduling". To effectively measure the results of this setting, tune the other I/O-related and thread-related configuration settings first.
• Reducing the amount of switching that InnoDB does between concurrent threads, so that SQL operations on a busy server do not queue up and form a "traffic jam". Set a value for the innodb_thread_concurrency option, up to approximately 32 for a high-powered modern system. Increase the value for the innodb_concurrency_tickets option, typically to 5000 or so, This combination of options sets a cap on the number of threads that InnoDB processes at any one time, and allows each thread to do substantial work before being swapped out, so that the number of waiting threads stays low and operations can complete without excessive context switching.

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