[kernel] Dynamically allocate task array from bootopts #1839
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First step, allocate fixed size array
Rewrite ps and memoinfo to handle variable sized task array Adjust SETUP_HEAPSIZE for minimal systems
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This enhancement allows the previously fixed maximum number of ELKS processes to be set in /bootopts, thus allowing for more tasks (sometimes useful in networking), or less (useful for systems with very small amounts of memory).
The default value is still 16. The task structure used to be contained in the kernel data segment, which subtracted from the available heap space used for other resources. It is now allocated from the kernel heap; with each task structure using 876 bytes, they are an expensive resource - 14016 bytes used. (More on PC-98 as its BIOS requires a larger stack size when performing disk I/O).
meminfonow shows the total task allocation bytes as a "TASK" entry so that memory usage can be seen.The implementation turned out a bit tricky, as the crt0.S startup code used to set the startup SP to the idle task's stack space. The kernel startup now uses the kernel interrupt stack for a temp stack, then switches stacks to the idle task after the /bootopts file has been read and the task array allocated.