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A physically indexed CPU cache is designed such that addresses in adjacent physical memory blocks take different positions ("cache lines") in the cache, but this is not the case when it comes to virtual memory; when virtually adjacent but not physically adjacent memory blocks are allocated, they could potentially both take the same position in the cache. Coloring is a technique implemented in memory management software, which solves this problem by selecting pages that do not contend with neighbor pages.
Physical memory pages are "colored" so that pages with different "colors" have different positions in CPU cache memory. When allocating sequential pages in virtual memory for processes, the kernel collects pages with different "colors" and maps them to the virtual memory. In this way, sequential pages in virtual memory do not contend for the same cache line.
Page Placement Algorithms for Large Real-Indexed Caches
" by R. E. Kessler, Mark D. Hill, University of Wisconsin, 1992.
" b
Jochen Liedtke
IBM T. J. Watson Center, Nov. 1996.
缓存着色技术
" by Maray, CSDN Technological Blog, 2008. {{DEFAULTSORT:Cache Coloring Cache (computing)
computer science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to Applied science, practical discipli ...
, cache coloring (also known as page coloring) is the process of attempting to allocate free pages
Page most commonly refers to:
* Page (paper), one side of a leaf of paper, as in a book
Page, PAGE, pages, or paging may also refer to:
Roles
* Page (assistance occupation), a professional occupation
* Page (servant), traditionally a young mal ...
that are contiguous from the CPU cache
A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost (time or energy) to access data from the main memory. A cache is a smaller, faster memory, located closer to a processor core, whi ...
's point of view, in order to maximize the total number of pages cached by the processor. Cache coloring is typically employed by low-level dynamic memory allocation
Memory management is a form of resource management applied to computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and free it for reuse when ...
code in the operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
, when mapping virtual memory
In computing, virtual memory, or virtual storage is a memory management technique that provides an "idealized abstraction of the storage resources that are actually available on a given machine" which "creates the illusion to users of a very ...
to physical memory. A virtual memory subsystem that lacks cache coloring is less deterministic with regards to cache performance, as differences in page allocation from one program run to the next can lead to large differences in program performance.
Details of operations
A physically indexed CPU cache is designed such that addresses in adjacent physical memory blocks take different positions ("cache lines") in the cache, but this is not the case when it comes to virtual memory; when virtually adjacent but not physically adjacent memory blocks are allocated, they could potentially both take the same position in the cache. Coloring is a technique implemented in memory management software, which solves this problem by selecting pages that do not contend with neighbor pages.
Physical memory pages are "colored" so that pages with different "colors" have different positions in CPU cache memory. When allocating sequential pages in virtual memory for processes, the kernel collects pages with different "colors" and maps them to the virtual memory. In this way, sequential pages in virtual memory do not contend for the same cache line.
Implementations
This code adds a significant amount of complexity to the virtual memory allocation subsystem, but the result is well worth the effort. Page coloring makes virtual memory as deterministic as physical memory with regard to cache performance. Page coloring is employed inoperating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
s such as Solaris, FreeBSD
FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...
, NetBSD
NetBSD is a free and open-source Unix operating system based on the Berkeley Software Distribution (BSD). It was the first open-source BSD descendant officially released after 386BSD was forked. It continues to be actively developed and is ava ...
,
and Windows NT
Windows NT is a proprietary graphical operating system produced by Microsoft, the first version of which was released on July 27, 1993. It is a processor-independent, multiprocessing and multi-user operating system.
The first version of Win ...
.
References
External links
Page Placement Algorithms for Large Real-Indexed Caches
" by R. E. Kessler, Mark D. Hill, University of Wisconsin, 1992.
" b
Jochen Liedtke
IBM T. J. Watson Center, Nov. 1996.
缓存着色技术
" by Maray, CSDN Technological Blog, 2008. {{DEFAULTSORT:Cache Coloring Cache (computing)