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vma目前有四种内存分配策略，这四种用法如下： * Support four policies per VMA and per process: * * The VMA policy has priority over the process policy for a page fault. * * interleave     Allocate memory interleaved over a set of nodes, *                with normal fallback if it fails. *                For VMA based allocations this interleaves based on the *                offset into the backing object or offset into the mapping *                for anonymous memory. For process policy an process counter *                is used. * * bind           Only allocate memory on a specific set of nodes, *                no fallback. *                FIXME: memory is allocated starting with the first node *                to the last. It would be better if bind would truly restrict *                the allocation to memory nodes instead * * preferred       Try a specific node first before normal fallback. *                As a special case NUMA_NO_NODE here means do the allocation *                on the local CPU. This is normally identical to default, *                but useful to set in a VMA when you have a non default *                process policy. * * default        Allocate on the local node first, or when on a VMA *                use the process policy. This is what Linux always did *		  in a NUMA aware kernel and still does by, ahem, default.在numa_policy_init 这个函数中会将所有numa节点的内存分配策略设置为MPOL_PREFERRED，即有限从指定的numa节点上分配内存。void __init numa_policy_init(void){	nodemask_t interleave_nodes;	unsigned long largest = 0;	int nid, prefer = 0;	#设置每个numa 节点的内存策略为MPOL_PREFERRED	for_each_node(nid) {		preferred_node_policy[nid] = (struct mempolicy) {			.refcnt = ATOMIC_INIT(1),			.mode = MPOL_PREFERRED,			.flags = MPOL_F_MOF | MPOL_F_MORON,			.v = { .preferred_node = nid, },		};	}	/*	 * Set interleaving policy for system init. Interleaving is only	 * enabled across suitably sized nodes (default is >= 16MB), or	 * fall back to the largest node if they're all smaller.	 */	#下面两种情况设置numa分配策略为interleave_nodes	nodes_clear(interleave_nodes);	for_each_node_state(nid, N_MEMORY) {		unsigned long total_pages = node_present_pages(nid);		/* Preserve the largest node */		if (largest < total_pages) {			largest = total_pages;			prefer = nid;		}		/* Interleave this node? */		#numa节点size 大于16M		if ((total_pages << PAGE_SHIFT) >= (16 << 20))			node_set(nid, interleave_nodes);	}	/* All too small, use the largest */	#如果所有的节点size 都要与16M，这样设置为interleave_nodes，以便系统用最大numa节点的memory	if (unlikely(nodes_empty(interleave_nodes)))		node_set(prefer, interleave_nodes);	#将前面已经更新好的interleave_nodes设为为MPOL_INTERLEAVE	if (do_set_mempolicy(MPOL_INTERLEAVE, 0, &interleave_nodes))		pr_err("%s: interleaving failed\n", __func__);	#检查是否开启numabalance	check_numabalancing_enable();}实际使用过程中可以通过get_task_policy 来得到task的内存分配策略struct mempolicy *get_task_policy(struct task_struct *p){	struct mempolicy *pol = p->mempolicy;	int node;	#task中保存的mempolicy 不为null的话，则直接返回	if (pol)		return pol;	#numa_node_id中调用raw_cpu_read(numa_node)来根据cpuid来得到当前的numa id	node = numa_node_id();	#如果task中的mempolicy为null，则返回numa_policy_init 中初始化的preferred_node_policy中当前task对应的node的mempolicy	if (node != NUMA_NO_NODE) {		pol = &preferred_node_policy[node];		/* preferred_node_policy is not initialised early in boot */		if (pol->mode)			return pol;	}	return &default_policy;}

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