Buffer pool like in every storage engine plays an important and pivotal role in Innodb engine. Buffer pool stands out as one of the most important component in storage engine's architecture.
Buffer pool is an area where frequently accessed data from tables and indexes is kept. When data is read from disk, it's loaded into the buffer pool, and subsequent reads can be served from memory instead of from disk which is the whole concept of creating a buffer pool. This can greatly improve performance because memory accesses are much faster than disk accesses.
The buffer pool is configurable, and its size is determined by the innodb_buffer_pool_size configuration option. The default value for this option is 128MB, but it's often recommended to increase it to several gigabytes for high-performance workloads. Out of many configurations the user can do according to its requirements are resizing the buffer pool, splitting the buffer pool into multiple parts to minimize memory contention, when and how to perform read-ahead requests to prefetch pages and when to perform flushing.
Buffer pool metrics can be monitored via Innodb standard monitor from which user can analyze the performance of buffer pool.
WORKING OF BUFFER POOL
When InnoDB needs to read data from a table or index, it first checks if the data is already in the buffer pool. If it is, the data can be read directly from memory. If not, InnoDB reads the data from disk and loads it into the buffer pool. If the buffer pool is full, InnoDB will evict some data to make room for the new data.
LRU (Least Recently Used) Algorithm is the backbone of eviction process through which data is stored in buffer pool.InnoDB keeps track of which pages in the buffer pool were accessed most recently and least recently, and when it needs to evict data, it chooses the least recently used pages to evict.
InnoDB also uses a technique called "adaptive flushing" to manage the buffer pool. When the buffer pool is full and new data needs to be loaded, InnoDB will first try to flush some dirty pages to disk. Dirty pages are pages that have been modified in memory but haven't yet been written to disk. By flushing these pages to disk, InnoDB can free up space in the buffer pool for new data.
Conclusion
The buffer pool is a critical component of InnoDB's architecture, and it's designed to improve performance by caching frequently accessed data in memory. By keeping data in memory, InnoDB can avoid disk accesses and serve requests much faster. The buffer pool is configurable, and its size should be set based on the workload and available memory. With a properly sized buffer pool, InnoDB can deliver excellent performance for transactional processing workloads.
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