MIT-SHM
Encyclopedia
The MIT Shared Memory Extension or MIT-SHM is a X Window System
extension for exchange of image data between client and server using shared memory
.
The basic capability provided is that of shared memory XImages. This is essentially a version of the ximage interface where the actual image data is stored in a SysV shared memory segment, and thus need not be transferred across the socket
to the X server. For large images, use of this facility can result in some real performance increases.
Additionally, some implementations provide shared memory pixmaps. These are 2 dimensional arrays of pixels in a format specified by the X server, where the image data is stored in the shared memory segment. Through use of shared memory pixmaps, it is possible to change the contents of these pixmaps without using any Xlib routines at all. Shared memory pixmaps can only be supported when the X server can use regular virtual memory for pixmap data; if the pixmaps are stored in the on-board memory of graphics hardware, an application will not be able to share them with the server.
X Window System
The X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
extension for exchange of image data between client and server using shared memory
Shared memory
In computing, shared memory is memory that may be simultaneously accessed by multiple programs with an intent to provide communication among them or avoid redundant copies. Depending on context, programs may run on a single processor or on multiple separate processors...
.
The basic capability provided is that of shared memory XImages. This is essentially a version of the ximage interface where the actual image data is stored in a SysV shared memory segment, and thus need not be transferred across the socket
Unix domain socket
A Unix domain socket or IPC socket is a data communications endpoint for exchanging data between processes executing within the same host operating system. While similar in functionality to...
to the X server. For large images, use of this facility can result in some real performance increases.
Additionally, some implementations provide shared memory pixmaps. These are 2 dimensional arrays of pixels in a format specified by the X server, where the image data is stored in the shared memory segment. Through use of shared memory pixmaps, it is possible to change the contents of these pixmaps without using any Xlib routines at all. Shared memory pixmaps can only be supported when the X server can use regular virtual memory for pixmap data; if the pixmaps are stored in the on-board memory of graphics hardware, an application will not be able to share them with the server.