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This diagram represents five contiguous memory regions which each hold a pointer and a data block. The List Head points to the 2nd element, which points to the 5th, which points to the 3rd, thereby forming a linked list of available memory regions. A free list (or freelist) is a data structure used in a scheme for dynamic memory allocation.
Since the memory would otherwise be idle and is easily reclaimed when applications request it, there is generally no associated performance penalty and the operating system might even report such memory as "free" or "available". When compared to main memory, hard disk drive read/writes are slow and random accesses require expensive disk seeks ...
Single allocation is the simplest memory management technique. All the computer's memory, usually with the exception of a small portion reserved for the operating system, is available to a single application. MS-DOS is an example of a system that allocates memory in this way. An embedded system running a single application might also use this ...
A separate array then stores the number of free sectors in each chunk, so chunks with insufficient space can be easily skipped over, and the total amount of free space is easier to compute. Finding free space now entails searching the summary array first, then searching the associated bitmap chunk for the exact sectors available. [1]
A highly available system would disable the malfunctioning portion and continue operating at a reduced capacity. In contrast, a less capable system might crash and become totally nonoperational. Availability is typically given as a percentage of the time a system is expected to be available, e.g., 99.999 percent ("five nines").
When the kernel swaps pages out of physical memory, it uses the highest-priority backend with available free space. If multiple swap backends are assigned the same priority, they are used in a round-robin fashion (which is somewhat similar to RAID 0 storage layouts), providing improved performance as long as the underlying devices can be ...
1) the mounted space of ramfs is theorically infinite, as ramfs will grow if needed, which can easily cause system lockup or crash for using up all available memory, or start heavy swapping to free up more memory for the ramfs. For this reason limiting the size of a ramfs area can be recommendable. 2) tmpfs is backed by the computer's swap space
Traditionally, low-memory-footprint programs were of importance to running applications on embedded systems where memory would often be a constrained resource [1] – so much so that developers typically sacrificed efficiency (processing speeds) just to make program footprints small enough to fit into the available RAM.