Linux 中带权内存交错分配实现方式

mm/mempolicy.c

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/*
 * Return a nodemask representing a mempolicy for filtering nodes for
 * page allocation, together with preferred node id (or the input node id).
 */
static nodemask_t *policy_nodemask(gfp_t gfp, struct mempolicy *pol,
				   pgoff_t ilx, int *nid)
{
	nodemask_t *nodemask = NULL;

	switch (pol->mode) {
	case MPOL_PREFERRED:
		/* Override input node id */
		*nid = first_node(pol->nodes);
		break;
	case MPOL_PREFERRED_MANY:
		nodemask = &pol->nodes;
		if (pol->home_node != NUMA_NO_NODE)
			*nid = pol->home_node;
		break;
	case MPOL_BIND:
		/* Restrict to nodemask (but not on lower zones) */
		if (apply_policy_zone(pol, gfp_zone(gfp)) &&
		    cpuset_nodemask_valid_mems_allowed(&pol->nodes))
			nodemask = &pol->nodes;
		if (pol->home_node != NUMA_NO_NODE)
			*nid = pol->home_node;
		/*
		 * __GFP_THISNODE shouldn't even be used with the bind policy
		 * because we might easily break the expectation to stay on the
		 * requested node and not break the policy.
		 */
		WARN_ON_ONCE(gfp & __GFP_THISNODE);
		break;
	case MPOL_INTERLEAVE:
		/* Override input node id */
		*nid = (ilx == NO_INTERLEAVE_INDEX) ?
			interleave_nodes(pol) : interleave_nid(pol, ilx);
		break;
	case MPOL_WEIGHTED_INTERLEAVE:
		*nid = (ilx == NO_INTERLEAVE_INDEX) ?
			weighted_interleave_nodes(pol) :
			weighted_interleave_nid(pol, ilx);
		break;
	}

	return nodemask;
}

当使用MPOL_WEIGHTED_INTERLEAVE时，节点的选择看ilx是否为NO_INTERLEAVE_INDXE

使用epbf进行内核插桩

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sudo bpftrace -e '                                             
kprobe:weighted_interleave_nodes {
    @nodes_stack[kstack, ustack] = count();
    @nodes_proc[comm, pid] = count();
}

kprobe:weighted_interleave_nid {
    @nid_stack[kstack, ustack] = count();
    @nid_proc[comm, pid] = count();
}

interval:s:5 {
    printf("\n=== %s ===\n", strftime("%H:%M:%S", nsecs));
    
    printf("=== Nodes - By Call Stack ===\n");
    print(@nodes_stack);
    printf("=== Nodes - By Process ===\n");
    print(@nodes_proc);
    
    printf("=== Nid - By Call Stack ===\n");
    print(@nid_stack);
    printf("=== Nid - By Process ===\n");
    print(@nid_proc);
    
    clear(@nodes_stack);
    clear(@nodes_proc);
    clear(@nid_stack);
    clear(@nid_proc);
}'

发现node和nid都会触发。
nid触发调用栈为：

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  @nid_stack[
        weighted_interleave_nid+1
        policy_nodemask+74
        alloc_pages_mpol+49
        vma_alloc_folio_noprof+110
        do_anonymous_page+810
        __handle_mm_fault+2667
        handle_mm_fault+170
        do_user_addr_fault+529
        exc_page_fault+116
        asm_exc_page_fault+38
, 
        0x55555556ecd1
        0
]: 1413

=== Nid - By Process ===
@nid_proc[numactl, 166213]: 1
@nid_proc[fuse, 166213]: 4
@nid_proc[lulesh2.0, 166213]: 45563

node触发调用栈为：

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@nodes_stack[
        weighted_interleave_nodes+1
        policy_nodemask+333
        alloc_pages_mpol+49
        alloc_pages_noprof+80
        pte_alloc_one+26
        do_huge_pmd_anonymous_page+207
        __handle_mm_fault+2789
        handle_mm_fault+170
        do_user_addr_fault+529
        exc_page_fault+116
        asm_exc_page_fault+38
, 
        __memset_avx512_unaligned_erms+361
        0
]: 8530
=== Nodes - By Process ===
@nodes_proc[lulesh2.0, 168848]: 8563
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