Memory Management

Query Execution
Updated on:
July 11, 2024

What is memory management?

Memory management is the process of coordinating the use of main memory storage to maximize utilization for active processes and data. It involves allocating memory on request, deallocating it when no longer needed, and organizing available memory for efficient access.

Memory managers handle requests from processes for blocks of memory and free memory for reuse once released. They organize free and allocated blocks efficiently using pooling, segmentation, paging and other techniques.

Efficient memory management is crucial for performance in database systems executing complex queries like in Apache DataFusion. The query execution framework and query optimization modules rely on memory management.

Memory for temporary runtime data like hashes, caches, and compiled user defined functions needs to be managed efficiently as well.

How does memory management work?

Typical memory management tasks include tracking available memory, allocating requested memory, mapping virtual to physical addresses, recovering unused memory, grouping memory blocks contiguously, swapping data to disk, and optimizing data layouts for access patterns.

Strategies include paging, segmentation, fragmentation avoidance and garbage collection. The operating system and language runtimes provide built-in memory management capabilities.

Why is memory management important? Where is it used?

Efficient memory usage is vital for system performance and stability. Ineffective memory management leads to issues like memory leaks, fragmentation, thrashing, allocation failures and out of memory errors.

Memory management is essential in operating systems, runtimes like Java Virtual Machine, web browsers, databases, and resource-constrained environments like embedded systems.


What are common memory management techniques?

Some key techniques are:

  • Paging - Mapping memory into fixed sized blocks
  • Segmentation - Dividing memory into variable sized blocks
  • Fragmentation avoidance - Coalescing free blocks
  • Caching - Frequently used data in faster memory
  • Garbage collection - Automatically freeing unused memory

What are the challenges in memory management?

Some key challenges include:

  • Fragmentation - Noncontiguous free memory
  • Thrashing - High paging overhead
  • Bottlenecks - Contention in multi-threaded apps
  • Leaks - Forgetting to free allocated memory
  • Bloat - Inefficient memory usage

How does memory management differ across languages?

Languages like C require manual memory management vs automatic garbage collection in Java, Python. Memory can be stack vs heap allocated. Some languages allow direct pointer manipulation.

What innovations are shaping modern memory management?

Advances in virtual memory, compressed pages, NUMA architecture, spoof detection, and cloud scale memory management for distributed systems.


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Related Entries

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Query optimization involves rewriting and transforming database queries to execute more efficiently by performing cost analysis to find faster query plans.

Execution Framework

An execution framework is a distributed system that automates and manages aspects like resource allocation, scheduling, fault tolerance and execution of large-scale computational jobs.

User Defined Functions (UDF)

A user-defined function (UDF) is a programming construct that allows developers to create custom functions in a database, query language or programming framework to extend built-in functionality.


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