Feat prevent ate memory from being swapped out

[Tomilla]

Hi Shawn:

New Feature:

• Memory read/write periodically, prevent memory from being swapped out

for i := range m.buffer {
	// XOR with 0 keeps the value unchanged but refresh the last modified time of memory
	m.buffer[i] ^= 0
}

start a goroutine to refresh(XOR with 0) the last modified time of every bytes of allocated memory. (a.k.a ActiveMemoryManager)

Performance Improved:

• Split user-request large memory to multiple small-size chunks(128MB by default)

Because available memory is not equal to contiguously allocatable memory due to memory fragmentation, So directly call make([]byte, m.size) with xxxGB may fail.

	// split request memory to multiple small-size chunks
	const unitChunk = chunkSizeMemoryWokerEachAllocate
	nChunks := m.size / unitChunk
	remain := m.size % unitChunk
	bufSizes := []uint64{}
	for i := uint64(0); i < nChunks; i++ {
		bufSizes = append(bufSizes, unitChunk)
	}
	if remain > 0 {
		bufSizes = append(bufSizes, remain)
	}

	fmt.Printf("Eating %-12sStart\n", "memory...")
	// Because free memory not equal to contiguous free memory, `make([]byte, m.size)` may fail
	// So we change the direct allocation to "divide and conquer", each time we only allocate small chunk of memory.
	m.buffers = make([][]byte, len(bufSizes))
	for i := range m.buffers {
		select {
		case <-ctx.Done():
			m.buffers = nil
			return errors.New("cancel allocation")
		default:
			//
		}
		curSize := bufSizes[i]
		curFreeSize = unimem.FreeMemory()
		if curSize > curFreeSize {
			m.buffers = nil
			return fmt.Errorf("free memory not enough: %d > %d", curSize, curFreeSize)
		}

		buffer := make([]byte, curSize)
		for i := range buffer {
			buffer[i] = byte(i % 256)
		}
		m.buffers[i] = buffer
	}

	fmt.Printf("Ate %d bytes memory\n", m.size)

Thanks for your review.

[shawn-bluce]

兄弟，真的太强了 行动力无敌 👍