kernel hacker修炼之道之内存管理-节点与管理区

浅析linux内核内存管理之节点与管理区

作者：李万鹏

void __init build_all_zonelists(void)
{
	int i;

	for_each_online_node(i)
		build_zonelists(NODE_DATA(i));
	printk("Built %i zonelists\n", num_online_nodes());
}

NUMA:

static int __init build_zonelists_node(pg_data_t *pgdat, struct zonelist *zonelist, int j, int k)
{
	switch (k) {
		struct zone *zone;
	default:
		BUG();
	case ZONE_HIGHMEM:
		zone = pgdat->node_zones + ZONE_HIGHMEM;
		if (zone->present_pages) {
#ifndef CONFIG_HIGHMEM
			BUG();
#endif
			zonelist->zones[j++] = zone;
		}
	case ZONE_NORMAL:
		zone = pgdat->node_zones + ZONE_NORMAL;
		if (zone->present_pages)
			zonelist->zones[j++] = zone;
	case ZONE_DMA:
		zone = pgdat->node_zones + ZONE_DMA;
		if (zone->present_pages)
			zonelist->zones[j++] = zone;
                                                                                                
	}

	return j;
}

static void __init build_zonelists(pg_data_t *pgdat)
{
	int i, j, k, node, local_node;

	local_node = pgdat->node_id;
	for (i = 0; i < GFP_ZONETYPES; i++) {
		struct zonelist *zonelist;

		zonelist = pgdat->node_zonelists + i;
		memset(zonelist, 0, sizeof(*zonelist));

		j = 0;
		k = ZONE_NORMAL;
		if (i & __GFP_HIGHMEM)
			k = ZONE_HIGHMEM;
		if (i & __GFP_DMA)
			k = ZONE_DMA;

 		j = build_zonelists_node(pgdat, zonelist, j, k);
 		/*
 		 * Now we build the zonelist so that it contains the zones
 		 * of all the other nodes.
 		 * We don't want to pressure a particular node, so when
 		 * building the zones for node N, we make sure that the
 		 * zones coming right after the local ones are those from
 		 * node N+1 (modulo N)
 		 */
		for (node = local_node + 1; node < MAX_NUMNODES; node++) {
			if (!node_online(node))
				continue;
			j = build_zonelists_node(NODE_DATA(node), zonelist, j, k);
		}
		for (node = 0; node < local_node; node++) {
			if (!node_online(node))
				continue;
			j = build_zonelists_node(NODE_DATA(node), zonelist, j, k);
		}

		zonelist->zones[j] = NULL;
	}
}

UMA:

#define node_distance(from,to)	((from) == (to) ? LOCAL_DISTANCE : REMOTE_DISTANCE)

static int __init find_next_best_node(int node, nodemask_t *used_node_mask)
{
	int i, n, val;
	int min_val = INT_MAX;
	int best_node = -1;

	for_each_online_node(i) {
		cpumask_t tmp;

		/* Start from local node */
		n = (node+i) % num_online_nodes();

		/* Don't want a node to appear more than once */
		if (node_isset(n, *used_node_mask))
			continue;

		/* Use the local node if we haven't already */
		if (!node_isset(node, *used_node_mask)) {
			best_node = node;
			break;
		}

		/* Use the distance array to find the distance */
		val = node_distance(node, n);

		/* Give preference to headless and unused nodes */
		tmp = node_to_cpumask(n);
		if (!cpus_empty(tmp))
			val += PENALTY_FOR_NODE_WITH_CPUS;

		/* Slight preference for less loaded node */
		val *= (MAX_NODE_LOAD*MAX_NUMNODES);
		val += node_load[n];

		if (val < min_val) {
			min_val = val;
			best_node = n;
		}
	}

	if (best_node >= 0)
		node_set(best_node, *used_node_mask);

	return best_node;
}

static void __init build_zonelists(pg_data_t *pgdat)
{
	int i, j, k, node, local_node;
	int prev_node, load;
	struct zonelist *zonelist;
	nodemask_t used_mask;

	/* initialize zonelists */
	for (i = 0; i < GFP_ZONETYPES; i++) {
		zonelist = pgdat->node_zonelists + i;
		memset(zonelist, 0, sizeof(*zonelist));
		zonelist->zones[0] = NULL;
	}

	/* NUMA-aware ordering of nodes */
	local_node = pgdat->node_id;
	load = num_online_nodes();
	prev_node = local_node;
	nodes_clear(used_mask);
	while ((node = find_next_best_node(local_node, &used_mask)) >= 0) {
		/*
		 * We don't want to pressure a particular node.
		 * So adding penalty to the first node in same
		 * distance group to make it round-robin.
		 */
		if (node_distance(local_node, node) !=
				node_distance(local_node, prev_node))
			node_load[node] += load;
		prev_node = node;
		load--;
		for (i = 0; i < GFP_ZONETYPES; i++) {
			zonelist = pgdat->node_zonelists + i;
			for (j = 0; zonelist->zones[j] != NULL; j++);

			k = ZONE_NORMAL;
			if (i & __GFP_HIGHMEM)
				k = ZONE_HIGHMEM;
			if (i & __GFP_DMA)
				k = ZONE_DMA;

	 		j = build_zonelists_node(NODE_DATA(node), zonelist, j, k);
			zonelist->zones[j] = NULL;
		}
	}
}

no discontig

void __init zone_sizes_init(void)
{
	unsigned long zones_size[MAX_NR_ZONES] = {0, 0, 0};
	unsigned int max_dma, high, low;
	
	max_dma = virt_to_phys((char *)MAX_DMA_ADDRESS) >> PAGE_SHIFT;
	low = max_low_pfn;
	high = highend_pfn;
	
	if (low < max_dma)
		zones_size[ZONE_DMA] = low;
	else {
		zones_size[ZONE_DMA] = max_dma;
		zones_size[ZONE_NORMAL] = low - max_dma;
#ifdef CONFIG_HIGHMEM
		zones_size[ZONE_HIGHMEM] = high - low;
#endif
	}
	free_area_init(zones_size);	
}

discontig

void __init zone_sizes_init(void)
{
	int nid;

	/*
	 * Insert nodes into pgdat_list backward so they appear in order.
	 * Clobber node 0's links and NULL out pgdat_list before starting.
	 */
	pgdat_list = NULL;
	for (nid = MAX_NUMNODES - 1; nid >= 0; nid--) {
		if (!node_online(nid))
			continue;
		if (nid)
			memset(NODE_DATA(nid), 0, sizeof(pg_data_t));
		NODE_DATA(nid)->pgdat_next = pgdat_list;
		pgdat_list = NODE_DATA(nid);
	}

	for_each_online_node(nid) {
		unsigned long zones_size[MAX_NR_ZONES] = {0, 0, 0};
		unsigned long *zholes_size;
		unsigned int max_dma;

		unsigned long low = max_low_pfn;
		unsigned long start = node_start_pfn[nid];
		unsigned long high = node_end_pfn[nid];

		max_dma = virt_to_phys((char *)MAX_DMA_ADDRESS) >> PAGE_SHIFT;

		if (start > low) {
#ifdef CONFIG_HIGHMEM
			BUG_ON(start > high);
			zones_size[ZONE_HIGHMEM] = high - start;
#endif
		} else {
			if (low < max_dma)
				zones_size[ZONE_DMA] = low;
			else {
				BUG_ON(max_dma > low);
				BUG_ON(low > high);
				zones_size[ZONE_DMA] = max_dma;
				zones_size[ZONE_NORMAL] = low - max_dma;
#ifdef CONFIG_HIGHMEM
				zones_size[ZONE_HIGHMEM] = high - low;
#endif
			}
		}
		zholes_size = get_zholes_size(nid);
		/*
		 * We let the lmem_map for node 0 be allocated from the
		 * normal bootmem allocator, but other nodes come from the
		 * remapped KVA area - mbligh
		 */
		if (!nid)
			free_area_init_node(nid, NODE_DATA(nid),
					zones_size, start, zholes_size);
		else {
			unsigned long lmem_map;
			lmem_map = (unsigned long)node_remap_start_vaddr[nid];
			lmem_map += sizeof(pg_data_t) + PAGE_SIZE - 1;
			lmem_map &= PAGE_MASK;
			NODE_DATA(nid)->node_mem_map = (struct page *)lmem_map;
			free_area_init_node(nid, NODE_DATA(nid), zones_size,
				start, zholes_size);
		}
	}
	return;
}