open-gpu-kernel-modules/kernel-open/nvidia-uvm/uvm_perf_utils.h

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    Copyright (c) 2015 NVIDIA Corporation

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#ifndef __UVM_PERF_UTILS_H__
#define __UVM_PERF_UTILS_H__

#include "uvm_common.h"

// Macros to perform increments that saturate at the maximum values allowed by the variable underlying storage
#define UVM_PERF_SATURATING_ADD(counter,value)     \
({                                                 \
    NvU64 expected;                                \
    NvU64 old;                                     \
                                                   \
    old = (counter);                               \
    expected = (NvU64)(counter) + (NvU64)(value);  \
    (counter) += (value);                          \
    if ((counter) != expected || expected < old)   \
        (counter) = -1;                            \
    (counter);                                     \
})

#define UVM_PERF_SATURATING_INC(counter) UVM_PERF_SATURATING_ADD((counter), 1)

// Array-based tree type for fix-sized binary trees. Nodes are stored in a contiguous array, ordered per level (from
// the leaf to the root). These trees are mainly used to keep statistics for memory regions. Stats are updated from a
// leaf node (which typically represents a page) up to the root of the tree (which represents the whole memory region
// tracked by the tree). Thus, statistics are transparently aggregated for different memory region size granularities.
//
// Restrictions: trees of up 63 levels are supported for 64-bit architectures, 31 levels for 32-bit architectures. This
// is because tree iterators use signed identifiers.

typedef struct
{
    // Number of leaves
    size_t leaf_count;

    // Number of node levels in the tree (32/64 maximum, so we can use a single byte)
    u8 level_count;

    // Total number of nodes (leaf + internal)
    size_t node_count;

    // Number of leaves that would make this tree a complete binary tree
    size_t pow2_leaf_count;

    void *nodes;
} uvm_perf_tree_t;

// Tree traversal
//
// Full- and complete-binary trees have properties that enable easy traversal of the tree using simple division and
// multiplication operations. However, forcing trees to be complete could leave to a huge waste of memory (up to 25%
// per tree). Therefore, tree traversals here need to compute the number of elements in the current/lower level before
// moving to the upper/lower level. Level 0 is the root level, (level_count - 1) is the leaves' level. This can be
// easily done with the following computation (see uvm_perf_tree_level_node_count):
//
// (1 << level) - (missing_leaves_to_pow2 >> ((levels - 1) - level))
//
// Once we have the offset to the beginning of the current level, we only need to add the index of the node visited
// within the current level. This is done as follows (see uvm_perf_tree_index_in_level):
//
// node_idx >> ((levels - 1) - level)
//
// We provide a type for tree traversals to allow macros to store the necessary information to transparently perform
// these computations. Thus, an uvm_perf_tree_iter_t object needs to be passed to the tree traversal macros.
typedef struct
{
    // For branch traversals: the index of the origin/destination leaf
    // For complete traversals: the index of the node in the current level
    ssize_t node_idx;

    // Current level in the traversal. Needs to be negative to allow detecting when we are out of bounds
    s8 level_idx;

    // Offset of the current level within the node array
    size_t level_offset;
} uvm_perf_tree_iter_t;

// Tree initialization. Computes the total number of levels and nodes required for the given number of leaf nodes and
// allocates its memory. Nodes' memory is zero-initialized.
//
// Returns NV_OK if initialization succeeded, or
// NV_ERR_NO_MEMORY if node allocation failed
NV_STATUS uvm_perf_tree_init(uvm_perf_tree_t *tree, size_t node_size, size_t leaf_count);

// Tree destruction. It frees the memory used by the nodes
void uvm_perf_tree_destroy(uvm_perf_tree_t *tree);

// Resets the contents of the nodes
void uvm_perf_tree_clear(uvm_perf_tree_t *tree, size_t node_size);

// Initializes the context for a tree traversal from the leaves to the root
static void uvm_perf_tree_init_up_traversal(const uvm_perf_tree_t *tree, uvm_perf_tree_iter_t *iter)
{
    iter->level_idx     = tree->level_count - 1;
    iter->level_offset  = 0;
}

static void uvm_perf_tree_init_up_branch_traversal(const uvm_perf_tree_t *tree, size_t leaf, uvm_perf_tree_iter_t *iter)
{
    uvm_perf_tree_init_up_traversal(tree, iter);

    iter->node_idx = leaf;
}

// Initializes the context for a tree traversal from the root to the leaves
static void uvm_perf_tree_init_down_traversal(const uvm_perf_tree_t *tree, uvm_perf_tree_iter_t *iter)
{
    iter->level_idx     = 0;
    iter->level_offset  = tree->node_count - 1;
}

static void uvm_perf_tree_init_down_branch_traversal(const uvm_perf_tree_t *tree, size_t leaf, uvm_perf_tree_iter_t *iter)
{
    uvm_perf_tree_init_down_traversal(tree, iter);

    iter->node_idx = leaf;
}

// Computes the index of the node visited for the traversal in the current level
static size_t uvm_perf_tree_iter_leaf_to_index_in_level(const uvm_perf_tree_t *tree, const uvm_perf_tree_iter_t *iter)
{
    return iter->node_idx >> ((tree->level_count - 1) - iter->level_idx);
}

// Computes the number of nodes in the given level
static size_t uvm_perf_tree_level_node_count(const uvm_perf_tree_t *tree, s8 level_idx)
{
    size_t level_pow2_node_count;
    size_t level_missing_nodes_to_pow2;

    if ((level_idx < 0) || (level_idx >= tree->level_count))
        return 0;

    level_pow2_node_count       = (size_t)1 << level_idx;
    level_missing_nodes_to_pow2 = (tree->pow2_leaf_count - tree->leaf_count) >> ((tree->level_count - 1) - level_idx);

    return level_pow2_node_count - level_missing_nodes_to_pow2;
}

// Function to compute the range of leaves that lie beneath any of the nodes in the tree.
//
// IMPORTANT: This functions may only be used in branch traversals
#define uvm_perf_tree_iter_max_leaves(tree, iter)                                    \
    ((typeof((tree)->leaf_count))1 << (((tree)->level_count - 1) - (iter)->level_idx))

#define uvm_perf_tree_iter_leaf_range_start(tree, iter)                             \
    UVM_ALIGN_DOWN((iter)->node_idx, uvm_perf_tree_iter_max_leaves((tree), (iter)))

#define uvm_perf_tree_iter_leaf_range(tree, iter)                                                     \
({                                                                                                    \
    typeof((tree)->leaf_count) __range_leaves  = uvm_perf_tree_iter_max_leaves((tree), (iter));       \
    typeof((tree)->leaf_count) __range_start   = uvm_perf_tree_iter_leaf_range_start((tree), (iter)); \
    typeof((tree)->leaf_count) __range_end_max = __range_start + __range_leaves;                      \
    typeof((tree)->leaf_count) __range_end     = min(__range_end_max, (tree)->leaf_count);            \
    __range_end - __range_start;                                                                      \
})

// Obtains the current node pointed by the traversal context when doing a branch traversal
#define UVM_PERF_TREE_ITER_BRANCH_CURRENT(tree,node_type,iter)                                                           \
({                                                                                                                       \
    (iter)->level_idx < 0 || (iter)->level_idx >= ((tree)->level_count) ?                                                \
        NULL:                                                                                                            \
        ((node_type *)(tree)->nodes) + (iter)->level_offset + uvm_perf_tree_iter_leaf_to_index_in_level((tree), (iter)); \
})

// Obtains the current node pointed by the traversal context when doing a full traversal
#define UVM_PERF_TREE_ITER_CURRENT(tree,node_type,iter)                         \
({                                                                              \
    (iter)->level_idx < 0 || (iter)->level_idx >= ((tree)->level_count) ?       \
        NULL:                                                                   \
        ((node_type *)(tree)->nodes) + (iter)->level_offset + (iter)->node_idx; \
})

// Obtains the leaf node corresponding to the given leaf node index
#define UVM_PERF_TREE_LEAF(tree,node_type,leaf_idx) \
({                                                  \
    ((node_type *)(tree)->nodes) + leaf_idx;        \
})

// Obtains the root node of the tree
#define UVM_PERF_TREE_ROOT(tree,node_type)                   \
({                                                           \
    ((node_type *)(tree)->nodes) + ((tree)->node_count - 1); \
})

// Functions to update the tree traversal context with the information of the next level (up/down)
static void uvm_perf_tree_traverse_up(const uvm_perf_tree_t *tree, uvm_perf_tree_iter_t *iter)
{
    // Nodes of the next level (up) are stored AFTER the current level
    iter->level_offset += uvm_perf_tree_level_node_count(tree, iter->level_idx--);
}

static void uvm_perf_tree_traverse_down(const uvm_perf_tree_t *tree, uvm_perf_tree_iter_t *iter)
{
    // Nodes of the next level (down) are stored BEFORE the current level. Since we are at the beginning of the current
    // level, we must skip all the nodes of the NEXT level.
    iter->level_offset -= uvm_perf_tree_level_node_count(tree, ++iter->level_idx);
}

// Complete branch traversal from the given leaf up to the root of the tree. A pointer to the node in each level of the
// traversal is stored in node
#define uvm_perf_tree_traverse_leaf_to_root(tree,leaf,node,iter)                      \
    for (uvm_perf_tree_init_up_branch_traversal((tree), (leaf), (iter)),              \
         (node) = UVM_PERF_TREE_ITER_BRANCH_CURRENT((tree), typeof(*(node)), (iter)); \
         (node) != NULL;                                                              \
         uvm_perf_tree_traverse_up((tree), (iter)),                                   \
         (node) = UVM_PERF_TREE_ITER_BRANCH_CURRENT((tree), typeof(*(node)), (iter)))

// Complete branch traversal from the root of the tree down to the given leaf index. A pointer to the node in each level
// of the traversal is stored in node
#define uvm_perf_tree_traverse_root_to_leaf(tree,leaf,node,iter)                      \
    for (uvm_perf_tree_init_down_branch_traversal((tree), (leaf), (iter)),            \
         (node) = UVM_PERF_TREE_ITER_BRANCH_CURRENT((tree), typeof(*(node)), (iter)); \
         (node) != NULL;                                                              \
         uvm_perf_tree_traverse_down((tree), (iter)),                                 \
         (node) = UVM_PERF_TREE_ITER_BRANCH_CURRENT((tree), typeof(*(node)), (iter)))

// Iterate over all tree levels from root to leaves
#define uvm_perf_tree_for_each_level_down(tree,iter)        \
    for (uvm_perf_tree_init_down_traversal((tree), (iter)); \
         (iter)->level_idx < (tree)->level_count;           \
         uvm_perf_tree_traverse_down((tree), (iter)))

// Iterate over all tree levels from leaves to root
#define uvm_perf_tree_for_each_level_up(tree,iter)        \
    for (uvm_perf_tree_init_up_traversal((tree), (iter)); \
         (iter)->level_idx >= 0;                          \
         uvm_perf_tree_traverse_up((tree), (iter)))

// Iterate over all nodes within a level of the tree (left to right)
#define uvm_perf_tree_level_for_each_node(tree,node,iter)                              \
    for ((iter)->node_idx = 0,                                                         \
         (node) = UVM_PERF_TREE_ITER_CURRENT((tree), typeof(*(node)), (iter));         \
         (iter)->node_idx < uvm_perf_tree_level_node_count((tree), (iter)->level_idx); \
         ++(iter)->node_idx,                                                           \
         ++(node))

// Iterate over all nodes within a level of the tree right to left
#define uvm_perf_tree_level_for_each_node_reverse(tree,node,iter)                          \
    for ((iter)->node_idx = uvm_perf_tree_level_node_count((tree), (iter)->level_idx) - 1, \
         (node) = UVM_PERF_TREE_ITER_CURRENT((tree), typeof(*(node)), (iter));             \
         (iter)->node_idx >= 0;                                                            \
         --(iter)->node_idx,                                                               \
         --(node))

#endif