10000 add support to split heap in multiple ranges · Issue #3758 · micropython/micropython · GitHub
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add support to split heap in multiple ranges #3758
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add support to split heap in multiple ranges#3758
@adritium

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@adritium
adritium
opened on May 3, 2018

In current gc initialization, it is only possible to provide one range for the heap.

micropython/py/gc.c

Lines 108 to 120 in 12a3fcc

void gc_init(void *start, void *end) {
// align end pointer on block boundary
end = (void*)((uintptr_t)end & (~(BYTES_PER_BLOCK - 1)));
DEBUG_printf("Initializing GC heap: %p..%p = " UINT_FMT " bytes\n", start, end, (byte*)end - (byte*)start);
// calculate parameters for GC (T=total, A=alloc table, F=finaliser table, P=pool; all in bytes):
// T = A + F + P
// F = A * BLOCKS_PER_ATB / BLOCKS_PER_FTB
// P = A * BLOCKS_PER_ATB * BYTES_PER_BLOCK
// => T = A * (1 + BLOCKS_PER_ATB / BLOCKS_PER_FTB + BLOCKS_PER_ATB * BYTES_PER_BLOCK)
size_t total_byte_len = (byte*)end - (byte*)start;
#if MICROPY_ENABLE_FINALISER
MP_STATE_MEM(gc_alloc_table_byte_len) = total_byte_len * BITS_PER_BYTE / (BITS_PER_BYTE + BITS_PER_BYTE * BLOCKS_PER_ATB / BLOCKS_PER_FTB + BITS_PER_BYTE * BLOCKS_PER_ATB * BYTES_PER_BLOCK);

However, all the RAM available on a micro-controller might not be in a contiguous range because there might be different types of RAM: SRAM, SDRAM, SPI-RAM, peripheral-dedicated RAM etc.

In my particular case, there is 4K of RAM that is used by a certain peripheral but only if it's enabled but otherwise, it's free for general-purpose use.
Unfortunately, 4K is too small for (most of) my uses as a heap by itself but if I could append it to my main heap, I wouldn't be letting 4K of RAM go to waste.

What do you think?

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