CooCox CoOS User's Guide

Assigned memory block list
50 100 210 315 372 569
50 100 210 315 372 569 623
100 210 315 372 569 623
Free memory block list
Figure 4.2.1 Memory management list
From the above, we can see that the free list will be divided into many small
pieces after allocating and releasing the memory many times. If you want to
apply for a large memory block at this time, the free list may not have the
fragment that meets user’s demand. This will lead to the so-called memory
fragmentation. In addition, the system needs to check the whole free list from
the beginning to determine the location that the memory block needs to plug in,
which leads the time of releasing the memory too long or uncertain.
CooCox CoOS provides two mechanisms of partitioning to solve these
problems: the partition of fixed length and the partition of variable length.
4.2.1 Fixed-length partition
It provides memory allocation mode of fixed length partition in CooCox
CoOS. The system will divide a large memory block into numbers of pieces
whose size are fixed, then link these pieces through the linked list. You can
allocate or release the memory block of fixed length through it. In this way, we
not only can ensure that the time of allocation or release is fixed, but also can
solve the problem of memory fragmentation.
P4.2.2 Partition of fixed length
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