path: root/storage/tokudb/ft-index/ft/serialize/block_allocator_strategy.cc

/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
// vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:

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  TokuFT, Tokutek Fractal Tree Indexing Library.
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*/

#include <algorithm>

#include <string.h>

#include "portability/toku_assert.h"

#include "ft/serialize/block_allocator_strategy.h"

static uint64_t _align(uint64_t value, uint64_t ba_alignment) {
    return ((value + ba_alignment - 1) / ba_alignment) * ba_alignment;
}

static uint64_t _roundup_to_power_of_two(uint64_t value) {
    uint64_t r = 4096;
    while (r < value) {
        r *= 2;
        invariant(r > 0);
    }
    return r;
}

// First fit block allocation
static struct block_allocator::blockpair *
_first_fit(struct block_allocator::blockpair *blocks_array,
           uint64_t n_blocks, uint64_t size, uint64_t alignment,
           uint64_t max_padding) {
    if (n_blocks == 1) {
        // won't enter loop, can't underflow the direction < 0 case
        return nullptr;
    }

    struct block_allocator::blockpair *bp = &blocks_array[0];
    for (uint64_t n_spaces_to_check = n_blocks - 1; n_spaces_to_check > 0;
         n_spaces_to_check--, bp++) {
        // Consider the space after bp
        uint64_t padded_alignment = max_padding != 0 ? _align(max_padding, alignment) : alignment;
        uint64_t possible_offset = _align(bp->offset + bp->size, padded_alignment);
        if (possible_offset + size <= bp[1].offset) { // bp[1] is always valid since bp < &blocks_array[n_blocks-1]
            invariant(bp - blocks_array < (int64_t) n_blocks);
            return bp;
        }
    }
    return nullptr;
}

static struct block_allocator::blockpair *
_first_fit_bw(struct block_allocator::blockpair *blocks_array,
           uint64_t n_blocks, uint64_t size, uint64_t alignment,
           uint64_t max_padding, struct block_allocator::blockpair *blocks_array_limit) {
    if (n_blocks == 1) {
        // won't enter loop, can't underflow the direction < 0 case
        return nullptr;
    }

    struct block_allocator::blockpair *bp = &blocks_array[-1];
    for (uint64_t n_spaces_to_check = n_blocks - 1; n_spaces_to_check > 0;
         n_spaces_to_check--, bp--) {
        // Consider the space after bp
        uint64_t padded_alignment = max_padding != 0 ? _align(max_padding, alignment) : alignment;
        uint64_t possible_offset = _align(bp->offset + bp->size, padded_alignment);
        if (&bp[1] < blocks_array_limit && possible_offset + size <= bp[1].offset) {
            invariant(blocks_array - bp < (int64_t) n_blocks);
            return bp;
        }
    }
    return nullptr;
}

struct block_allocator::blockpair *
block_allocator_strategy::first_fit(struct block_allocator::blockpair *blocks_array,
                                    uint64_t n_blocks, uint64_t size, uint64_t alignment) {
    return _first_fit(blocks_array, n_blocks, size, alignment, 0);
}

// Best fit block allocation
struct block_allocator::blockpair *
block_allocator_strategy::best_fit(struct block_allocator::blockpair *blocks_array,
                                   uint64_t n_blocks, uint64_t size, uint64_t alignment) {
    struct block_allocator::blockpair *best_bp = nullptr;
    uint64_t best_hole_size = 0;
    for (uint64_t blocknum = 0; blocknum + 1 < n_blocks; blocknum++) {
        // Consider the space after blocknum
        struct block_allocator::blockpair *bp = &blocks_array[blocknum];
        uint64_t possible_offset = _align(bp->offset + bp->size, alignment);
        uint64_t possible_end_offset = possible_offset + size;
        if (possible_end_offset <= bp[1].offset) {
            // It fits here. Is it the best fit?
            uint64_t hole_size = bp[1].offset - possible_end_offset;
            if (best_bp == nullptr || hole_size < best_hole_size) {
                best_hole_size = hole_size;
                best_bp = bp;
            }
        }
    }
    return best_bp;
}

static uint64_t padded_fit_alignment = 4096;

// TODO: These compiler specific directives should be abstracted in a portability header
//       portability/toku_compiler.h?
__attribute__((__constructor__))
static void determine_padded_fit_alignment_from_env(void) {
    // TODO: Should be in portability as 'toku_os_getenv()?'
    const char *s = getenv("TOKU_BA_PADDED_FIT_ALIGNMENT");
    if (s != nullptr && strlen(s) > 0) {
        const int64_t alignment = strtoll(s, nullptr, 10);
        if (alignment <= 0) {
            fprintf(stderr, "tokuft: error: block allocator padded fit alignment found in environment (%s), "
                            "but it's out of range (should be an integer > 0). defaulting to %" PRIu64 "\n",
                            s, padded_fit_alignment);
        } else {
            padded_fit_alignment = _roundup_to_power_of_two(alignment);
            fprintf(stderr, "tokuft: setting block allocator padded fit alignment to %" PRIu64 "\n",
                    padded_fit_alignment);
        }
    }
}

// First fit into a block that is oversized by up to max_padding.
// The hope is that if we purposefully waste a bit of space at allocation
// time we'll be more likely to reuse this block later.
struct block_allocator::blockpair *
block_allocator_strategy::padded_fit(struct block_allocator::blockpair *blocks_array,
                                     uint64_t n_blocks, uint64_t size, uint64_t alignment) {
    return _first_fit(blocks_array, n_blocks, size, alignment, padded_fit_alignment);
}

static double hot_zone_threshold = 0.85;

// TODO: These compiler specific directives should be abstracted in a portability header
//       portability/toku_compiler.h?
__attribute__((__constructor__))
static void determine_hot_zone_threshold_from_env(void) {
    // TODO: Should be in portability as 'toku_os_getenv()?'
    const char *s = getenv("TOKU_BA_HOT_ZONE_THRESHOLD");
    if (s != nullptr && strlen(s) > 0) {
        const double hot_zone = strtod(s, nullptr);
        if (hot_zone < 1 || hot_zone > 99) {
            fprintf(stderr, "tokuft: error: block allocator hot zone threshold found in environment (%s), "
                            "but it's out of range (should be an integer 1 through 99). defaulting to 85\n", s);
            hot_zone_threshold = 85 / 100;
        } else {
            fprintf(stderr, "tokuft: setting block allocator hot zone threshold to %s\n", s);
            hot_zone_threshold = hot_zone / 100;
        }
    }
}

struct block_allocator::blockpair *
block_allocator_strategy::heat_zone(struct block_allocator::blockpair *blocks_array,
                                    uint64_t n_blocks, uint64_t size, uint64_t alignment,
                                    uint64_t heat) {
    if (heat > 0) {
        struct block_allocator::blockpair *bp, *boundary_bp;

        // Hot allocation. Find the beginning of the hot zone.
        boundary_bp = &blocks_array[n_blocks - 1];
        uint64_t highest_offset = _align(boundary_bp->offset + boundary_bp->size, alignment);
        uint64_t hot_zone_offset = static_cast<uint64_t>(hot_zone_threshold * highest_offset);

        boundary_bp = std::lower_bound(blocks_array, blocks_array + n_blocks, hot_zone_offset);
        uint64_t blocks_in_zone = (blocks_array + n_blocks) - boundary_bp;
        uint64_t blocks_outside_zone = boundary_bp - blocks_array;
        invariant(blocks_in_zone + blocks_outside_zone == n_blocks);

        if (blocks_in_zone > 0) {
            // Find the first fit in the hot zone, going forward.
            bp = _first_fit(boundary_bp, blocks_in_zone, size, alignment, 0);
            if (bp != nullptr) {
                return bp;
            }
        }
        if (blocks_outside_zone > 0) {
            // Find the first fit in the cold zone, going backwards.
            bp = _first_fit_bw(boundary_bp, blocks_outside_zone, size, alignment, 0, &blocks_array[n_blocks]);
            if (bp != nullptr) {
                return bp;
            }
        }
    } else {
        // Cold allocations are simply first-fit from the beginning.
        return _first_fit(blocks_array, n_blocks, size, alignment, 0);
    }
    return nullptr;
}