RTOS memory footprint
First, there is the question of what kind of memory we want to consider. Broadly speaking, there is ROM [nowadays that is usually flash memory] and RAM. ROM is where the code and constant data is stored; RAM is used for variables. However, to improve performance, it is not uncommon to copy code/data from ROM to RAM on boot up and then use the RAM copy. This is effective because RAM is normally faster to access than ROM. So, when thinking about of RTOS footprint, you need to consider ROM and RAM size, including the RAM copy possibility.
The size of the code can vary for a selection of reasons:
CPU architecture has a drastic influence. Code size for PowerPC, for example, is likely to be very different from ARM. Code built for Thumb-2 is likely to be significantly smaller than ARM.
Compiler optimization affects both size and execution speed. Most of the time, code built for highest performance [i.e. fastest] will be bigger; code optimized to be smaller will run slower. It is most likely that an RTOS would normally be built for performance, not size.
The configuration of the RTOS can vary its size drastically. Most RTOSes are scalable, so the memory footprint is determined by the actual services used by the application. On a larger scale, other options, like networking, will affect the code size.
Typically, a runtime library will be used alongside an RTOS; this code needs to be accommodated.
Apart from a baseline amount of storage for variables, the RAM requirements of an RTOS can similarly be affected by a number of factors:
Compiler optimization also affects data size. Packed data is smaller, but takes more instructions to access.
The number of RTOS objects [tasks, mailboxes, semaphores etc.] used by the application will affect the RTOS RAM usage – each object needs some RAM space.
Normally, every task has its own stack, which must be stored in RAM. Allocation of this space may be done differently in a number of RTOSes, but it can never be ignored.
If dynamic memory allocation is used by the application, space for memory pools needs to be accommodated.
Compiler optimization affects both size and execution speed. Most of the time, code built for highest performance [i.e. fastest] will be bigger; code optimized to be smaller will run slower. It is most likely that an RTOS would normally be built for performance, not size.
The configuration of the RTOS can vary its size drastically. Most RTOSes are scalable, so the memory footprint is determined by the actual services used by the application. On a larger scale, other options, like networking, will affect the code size.
Typically, a runtime library will be used alongside an RTOS; this code needs to be accommodated.
Compiler optimization affects both size and execution speed. Most of the time, code built for highest performance [i.e. fastest] will be bigger; code optimized to be smaller will run slower. It is most likely that an RTOS would normally be built for performance, not size.
The configuration of the RTOS can vary its size drastically. Most RTOSes are scalable, so the memory footprint is determined by the actual services used by the application. On a larger scale, other options, like networking, will affect the code size.
Typically, a runtime library will be used alongside an RTOS; this code needs to be accommodated.
A real-time operating system (RTOS) is an operating system that guarantees a certain capability within a specified time constraint. For example, an operating system might be designed to ensure that a certain object was available for a robot on an assembly line. In what is usually called a “hard” real-time operating system, if the calculation could not be performed for making the object available at the designated time, the operating system would terminate with a failure. In a “soft” real-time operating system, the assembly line would continue to function but the production output might be lower as objects failed to appear at their designated time, causing the robot to be temporarily unproductive. Some real-time operating systems are created for a special application and others are more general purpose.
RTOS memory footprint
First, there is the question of what kind of memory we want to consider. Broadly speaking, there is ROM [nowadays that is usually flash memory] and RAM. ROM is where the code and constant data is stored; RAM is used for variables. However, to improve performance, it is not uncommon to copy code/data from ROM to RAM on boot up and then use the RAM copy. This is effective because RAM is normally faster to access than ROM. So, when thinking about of RTOS footprint, you need to consider ROM and RAM size, including the RAM copy possibility.
The size of the code can vary for a selection of reasons:
CPU architecture has a drastic influence. Code size for PowerPC, for example, is likely to be very different from ARM. Code built for Thumb-2 is likely to be significantly smaller than ARM.
Compiler optimization affects both size and execution speed. Most of the time, code built for highest performance [i.e. fastest] will be bigger; code optimized to be smaller will run slower. It is most likely that an RTOS would normally be built for performance, not size.
The configuration of the RTOS can vary its size drastically. Most RTOSes are scalable, so the memory footprint is determined by the actual services used by the application. On a larger scale, other options, like networking, will affect the code size.
Typically, a runtime library will be used alongside an RTOS; this code needs to be accommodated.
Apart from a baseline amount of storage for variables, the RAM requirements of an RTOS can similarly be affected by a number of factors:
Compiler optimization also affects data size. Packed data is smaller, but takes more instructions to access.
The number of RTOS objects [tasks, mailboxes, semaphores etc.] used by the application will affect the RTOS RAM usage – each object needs some RAM space.
Normally, every task has its own stack, which must be stored in RAM. Allocation of this space may be done differently in a number of RTOSes, but it can never be ignored.
If dynamic memory allocation is used by the application, space for memory pools needs to be accommodated.
Compiler optimization affects both size and execution speed. Most of the time, code built for highest performance [i.e. fastest] will be bigger; code optimized to be smaller will run slower. It is most likely that an RTOS would normally be built for performance, not size.
The configuration of the RTOS can vary its size drastically. Most RTOSes are scalable, so the memory footprint is determined by the actual services used by the application. On a larger scale, other options, like networking, will affect the code size.
Typically, a runtime library will be used alongside an RTOS; this code needs to be accommodated.
real time operating systems.it mostly used all embedded systems.
real time operating systems
R.CHANDRASEKAR
Compiler optimization affects both size and execution speed. Most of the time, code built for highest performance [i.e. fastest] will be bigger; code optimized to be smaller will run slower. It is most likely that an RTOS would normally be built for performance, not size.
The configuration of the RTOS can vary its size drastically. Most RTOSes are scalable, so the memory footprint is determined by the actual services used by the application. On a larger scale, other options, like networking, will affect the code size.
Typically, a runtime library will be used alongside an RTOS; this code needs to be accommodated.
A real-time operating system (RTOS) is an operating system that guarantees a certain capability within a specified time constraint. For example, an operating system might be designed to ensure that a certain object was available for a robot on an assembly line. In what is usually called a “hard” real-time operating system, if the calculation could not be performed for making the object available at the designated time, the operating system would terminate with a failure. In a “soft” real-time operating system, the assembly line would continue to function but the production output might be lower as objects failed to appear at their designated time, causing the robot to be temporarily unproductive. Some real-time operating systems are created for a special application and others are more general purpose.