In computing, proportional set size (PSS) is the portion of main memory (
RAM
Ram, ram, or RAM may refer to:
Animals
* A male sheep
* Ram cichlid, a freshwater tropical fish
People
* Ram (given name)
* Ram (surname)
* Ram (director) (Ramsubramaniam), an Indian Tamil film director
* RAM (musician) (born 1974), Dutch
* Ra ...
) occupied by a process and is composed by the private memory of that process plus the proportion of shared memory with one or more other processes. Unshared memory including the proportion of shared memory is reported as the PSS.
Example:
* Process A has 50
KiB
The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit ...
of unshared memory
* Process B has 300 KiB of unshared memory
* Both process A and process B have 100 KiB of the same shared memory region
Since the PSS is defined as the sum of the unshared memory of a process and the proportion of memory shared with other processes, the PSS for these two processes are as follows:
* PSS of process A = 50 KiB + (100 KiB / 2) = 100 KiB
* PSS of process B = 300 KiB + (100 KiB / 2) = 350 KiB
This concept is mostly related (if not unique) to the
Linux operating system
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...
. It was proposed by Matt Mackall
because of the complications that arose when trying to count the "real memory" used by a process. The concepts of
resident set size
In computing, resident set size (RSS) is the portion of memory occupied by a process that is held in main memory (RAM). The rest of the occupied memory exists in the swap space or file system, either because some parts of the occupied memory were ...
or virtual memory size (VmSize) weren't helping developers who tried to know how much memory their programs were using.
See also
*
Unique set size
*
Resident set size
In computing, resident set size (RSS) is the portion of memory occupied by a process that is held in main memory (RAM). The rest of the occupied memory exists in the swap space or file system, either because some parts of the occupied memory were ...
References
{{Reflist
External links
PSS (Proportional Set Size) CalculationHow much memory are applications really using?
Memory management