Working Set Size
Encyclopedia
In computing the working set size is the amount of memory needed to compute the answer to a problem. In any computing scenario, but especially high performance computing where mistakes can be costly, this is a significant design-criteria for a given super computer system in order to ensure that the system performs as expected.
When a program/algorithm
computes the answer to a problem it uses a set of data
(input and intermediate data) to complete the work. For a given instance of a problem and program combination the size of this data set is the working set
. The Working Set Size (WSS) is then the size of the data set.
The significance of this is that if the Working Set Size is larger than the available memory in a virtual memory
system then the memory manager must refer to the next level in the memory hierarchy (usually hard disk
) to perform a swap operation swapping some memory contents from RAM
to hard disk
to enable the program to continue working on the problem. If this swapping goes on continuously the program is slowed down significantly. This phenomenon is known as thrashing.
When a program/algorithm
Algorithm
In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...
computes the answer to a problem it uses a set of data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
(input and intermediate data) to complete the work. For a given instance of a problem and program combination the size of this data set is the working set
Working set
Peter Denning defines “the working set of information W of a process at time t to be the collection of information referenced by the process during the process time interval ”. Typically the units of information in question are considered to be memory pages...
. The Working Set Size (WSS) is then the size of the data set.
The significance of this is that if the Working Set Size is larger than the available memory in a virtual memory
Virtual memory
In computing, virtual memory is a memory management technique developed for multitasking kernels. This technique virtualizes a computer architecture's various forms of computer data storage , allowing a program to be designed as though there is only one kind of memory, "virtual" memory, which...
system then the memory manager must refer to the next level in the memory hierarchy (usually hard disk
Hard disk
A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...
) to perform a swap operation swapping some memory contents from RAM
Ram
-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...
to hard disk
Hard disk
A hard disk drive is a non-volatile, random access digital magnetic data storage device. It features rotating rigid platters on a motor-driven spindle within a protective enclosure. Data is magnetically read from and written to the platter by read/write heads that float on a film of air above the...
to enable the program to continue working on the problem. If this swapping goes on continuously the program is slowed down significantly. This phenomenon is known as thrashing.