open-gpu-kernel-modules/kernel-open/nvidia-uvm/uvm_range_allocator.c

/*******************************************************************************
    Copyright (c) 2016 NVIDIA Corporation

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        The above copyright notice and this permission notice shall be
        included in all copies or substantial portions of the Software.

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    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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#include "uvm_range_allocator.h"
#include "uvm_kvmalloc.h"

NV_STATUS uvm_range_allocator_init(NvU64 size, uvm_range_allocator_t *range_allocator)
{
    NV_STATUS status;
    uvm_range_tree_node_t *node;

    uvm_spin_lock_init(&range_allocator->lock, UVM_LOCK_ORDER_LEAF);
    uvm_range_tree_init(&range_allocator->range_tree);

    UVM_ASSERT(size > 0);

    node = uvm_kvmalloc(sizeof(*node));
    if (!node)
        return NV_ERR_NO_MEMORY;

    node->start = 0;
    node->end = size - 1;

    status = uvm_range_tree_add(&range_allocator->range_tree, node);
    UVM_ASSERT(status == NV_OK);

    range_allocator->size = size;

    return NV_OK;
}

void uvm_range_allocator_deinit(uvm_range_allocator_t *range_allocator)
{
    uvm_range_tree_node_t *node;

    node = uvm_range_tree_iter_first(&range_allocator->range_tree, 0, range_allocator->size - 1);
    UVM_ASSERT(node);
    UVM_ASSERT_MSG(node->start == 0 && node->end == range_allocator->size - 1, "start 0x%llx end 0x%llx\n", node->start, node->end);

    // Remove the node for completeness even though after deinit the state of
    // tree doesn't matter anyway.
    uvm_range_tree_remove(&range_allocator->range_tree, node);

    uvm_kvfree(node);
}

NV_STATUS uvm_range_allocator_alloc(uvm_range_allocator_t *range_allocator, NvU64 size, NvU64 alignment, uvm_range_allocation_t *range_alloc)
{
    uvm_range_tree_node_t *node;
    bool found = false;

    UVM_ASSERT(size > 0);

    if (alignment == 0)
        alignment = 1;

    UVM_ASSERT(is_power_of_2(alignment));

    if (size > range_allocator->size)
        return NV_ERR_UVM_ADDRESS_IN_USE;

    // Pre-allocate a tree node as part of the allocation so that freeing the
    // range won't require allocating memory and will always succeed.
    range_alloc->node = uvm_kvmalloc(sizeof(*range_alloc->node));
    if (!range_alloc->node)
        return NV_ERR_NO_MEMORY;

    uvm_spin_lock(&range_allocator->lock);

    // This is a very simple brute force going over all the free ranges in
    // address order and returning the first one that's big enough.
    // This could be improved by e.g. also maintaining a binary tree of free
    // ranges ordered by their size.
    uvm_range_tree_for_each_in(node, &range_allocator->range_tree, 0, range_allocator->size - size) {
        NvU64 aligned_start = UVM_ALIGN_UP(node->start, alignment);
        NvU64 aligned_end = aligned_start + size - 1;

        // Check for overflow of aligned_start and aligned_end
        if (aligned_start < node->start || aligned_end < aligned_start)
            continue;

        // Check whether it fits
        if (aligned_end > node->end)
            continue;

        // The allocation always wastes the [node->start, aligned_start) space,
        // but it's expected that there will always be plenty of free space to
        // allocate from and wasting that space should help avoid fragmentation.

        range_alloc->aligned_start = aligned_start;
        range_alloc->node->start = node->start;
        range_alloc->node->end = aligned_end;

        if (aligned_end < node->end) {
            // Shrink the node if the claimed size is smaller than the node.
            uvm_range_tree_shrink_node(&range_allocator->range_tree, node, aligned_end + 1, node->end);
        }
        else {
            // Otherwise just remove it. The removal is safe to do in the loop
            // over nodes as a break is following immediately.
            UVM_ASSERT(node->end == aligned_end);
            uvm_range_tree_remove(&range_allocator->range_tree, node);
            uvm_kvfree(node);
        }
        found = true;
        break;
    }

    uvm_spin_unlock(&range_allocator->lock);

    if (!found) {
        uvm_kvfree(range_alloc->node);
        range_alloc->node = NULL;
        return NV_ERR_UVM_ADDRESS_IN_USE;
    }

    return NV_OK;
}

void uvm_range_allocator_free(uvm_range_allocator_t *range_allocator, uvm_range_allocation_t *range_alloc)
{
    NV_STATUS status;
    uvm_range_tree_node_t *adjacent_node;

    if (!range_alloc)
        return;

    UVM_ASSERT(range_alloc->node);

    uvm_spin_lock(&range_allocator->lock);

    // Add the pre-allocated free range to the tree
    status = uvm_range_tree_add(&range_allocator->range_tree, range_alloc->node);
    UVM_ASSERT(status == NV_OK);

    // And try merging it with adjacent nodes
    adjacent_node = uvm_range_tree_merge_prev(&range_allocator->range_tree, range_alloc->node);
    if (adjacent_node)
        uvm_kvfree(adjacent_node);

    adjacent_node = uvm_range_tree_merge_next(&range_allocator->range_tree, range_alloc->node);
    if (adjacent_node)
        uvm_kvfree(adjacent_node);

    uvm_spin_unlock(&range_allocator->lock);

    range_alloc->node = NULL;
}