Dynamic memory allocation has been a fundamental part of most computer systems since roughly 1960, and memory allocation is widely considered to be either a solved problem or an insoluble one. In this survey, we describe a variety of memory allocator designs and point out issues relevant to their design and evaluation. We then chronologically survey most of the literature on allocators between 1961 and 1995. (Scores of papers are discussed, in varying detail, and over 150 references are given.)

/pdf/dynamic-storage-allocation-a-survey-and-critical-review-2mi0efvca4.pdf

Dynamic Storage Allocation: A Survey and Critical Review

Jobs that do not require all processors in the system can be packed together for gang scheduling. We examine accounting traces from several parallel computers to show that indeed many jobs have small sizes and can be packed together. We then formulate a number of such packing algorithms, and evaluate their effectiveness using simulations based on our workload study. The results are that two algorithms are the best: either perform the mapping based on a buddy system of processors, or use migration to re-map the jobs more tightly whenever a job arrives or terminates. Other approaches, such as mapping to the least loaded PEs, proved to be counterproductive. The buddy system approach depends on the capability to gang-schedule jobs in multiple slots, if there is space. The migration algorithm is more robust, but is expected to suffer greatly due to the overhead of the migration itself. In either case fragmentation is not an issue, and utilization may top 90% with sufficiently high loads.

Packing Schemes for Gang Scheduling

Two algorithms are presented for implementing any of a class of buddy systems for dynamic storage allocation. Each buddy system corresponds to a set of recurrence relations which relate the block sizes provided to each other. Analyses of the internal fragmentation of the binary buddy system, the Fibonacci buddy system, and the weighted buddy system are given. Comparative simulation results are also presented for internal, external, and total fragmentation.

Buddy systems

Evaluation of Design Choices for Gang Scheduling Using Distributed Hierarchical Control

The buddy system is known for its speed and simplicity. However, high internal and external fragmentation have made it unattractive for use in operating system file layout. A variant of the binary buddy system that reduces fragmentation is described. Files are allocated on up to t extents, and inoptimally allocated files are periodically reallocated. The Dartmouth Time-Sharing System (DTSS) uses this method. Several installations of DTSS, representing different classes of workload, are studied to measure the method's performance. Internal fragmentation varies from 2-6 percent, and external fragmentation varies from 0-10 percent for expected request sizes. Less than 0.1 percent of the CPU is spent executing the algorithm. In addition, most files are stored contiguously on disk. The mean number of extents per file is less than 1.5, and the upper bound is t. Compared to the tile layout method used by UNIX, the buddy system results in more efficient access but less efficient utilization of disk space. As disks become larger and less expensive per byte, strategies that achieve efficient I/O throughput at the expense of some storage loss become increasingly attractive.

Disk file allocation based on the buddy system

A general class of buddy systems is defined and the overallocation of memory due to internal fragmentation is examined. It is shown that, for a uniform distribution of requests, the overallocation varies between $2x_{1}/(x_{1}+1)$ and $\frac{1}{2}(x_{1}+1)$, where $x_{1}>1$ is the largest real root of the characteristic equation of the particular buddy system. Bounds are found for the overallocation for request distributions characterized by a parameterization of Zipf’s law. The expected value of the overallocation is independent of the request distribution within wide values of the parameter, and is given by $(x_{1}-1)/\ln x_{1}$. For the binary buddy system $x_{1}= 2$; the overallocation varies between 1.33 and 1.50 and the expected value is $\approx 1.44$.

Internal Fragmentation in a Class of Buddy Systems

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

David L. Russell

Author Tools

Chat about Author

Papers

Internal Fragmentation in a Class of Buddy Systems