slock - My personal fork of the slock screen locker

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author	Markus Teich <markus.teich@stusta.mhn.de>	2016-02-11 16:26:12 +0100
committer	Markus Teich <markus.teich@stusta.mhn.de>	2016-02-11 16:26:12 +0100
commit	f6582b68b03fe25fe0296b685af6b5924cca7df9 (patch)
tree	28eaea01de4bdcfb78e568885e533bc4fd18ab4f
parent	bfafc91da7b51be4e1543b64ee118fff2e3a4cfb (diff)
download	slock-f6582b68b03fe25fe0296b685af6b5924cca7df9.tar.gz

update copyright year in -v output

Diffstat

-rw-r--r--

slock.c

1 files changed, 1 insertions, 1 deletions

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/*
 * include/framework/structure/ExtensionStructure.h
 *
 * Copyright (C) 2023 Douglas B. Rumbaugh <drumbaugh@psu.edu> 
 *                    Dong Xie <dongx@psu.edu>
 *
 * Distributed under the Modified BSD License.
 *
 */
#pragma once

#include <atomic>
#include <cstdio>
#include <vector>

#include "framework/structure/BufferView.h"
#include "framework/structure/InternalLevel.h"

#include "framework/util/Configuration.h"

#include "psu-util/timer.h"

namespace de {

template <RecordInterface R, ShardInterface<R> S, QueryInterface<R, S> Q, LayoutPolicy L=LayoutPolicy::TEIRING>
class ExtensionStructure {
    typedef S Shard;
    typedef BufferView<R> BuffView;

    typedef struct {
        size_t reccnt;
        size_t reccap;

        size_t shardcnt;
        size_t shardcap;
    } level_state;

    typedef std::vector<level_state> state_vector;

public:
    ExtensionStructure(size_t buffer_size, size_t scale_factor, double max_delete_prop)
        : m_scale_factor(scale_factor)
        , m_max_delete_prop(max_delete_prop)
        , m_buffer_size(buffer_size)
    {}

    ~ExtensionStructure() = default;

    /*
     * Create a shallow copy of this extension structure. The copy will share
     * references to the same levels/shards as the original, but will have its
     * own lists. As all of the shards are immutable (with the exception of
     * deletes), the copy can be restructured with reconstructions and flushes
     * without affecting the original. The copied structure will be returned
     * with a reference count of 0; generally you will want to immediately call
     * take_reference() on it.
     *
     * NOTE: When using tagged deletes, a delete of a record in the original
     * structure will affect the copy, so long as the copy retains a reference
     * to the same shard as the original. This could cause synchronization
     * problems under tagging with concurrency. Any deletes in this context will
     * need to be forwarded to the appropriate structures manually.
     */
    ExtensionStructure<R, S, Q, L> *copy() {
        auto new_struct = new ExtensionStructure<R, S, Q, L>(m_buffer_size, m_scale_factor, 
                                                             m_max_delete_prop);
        for (size_t i=0; i<m_levels.size(); i++) {
            new_struct->m_levels.push_back(m_levels[i]->clone());
        }

        new_struct->m_refcnt = 0;
        new_struct->m_current_state = m_current_state;

        return new_struct;
    }

    /*
     * Search for a record matching the argument and mark it deleted by
     * setting the delete bit in its wrapped header. Returns 1 if a matching
     * record was found and deleted, and 0 if a matching record was not found.
     *
     * This function will stop after finding the first matching record. It is
     * assumed that no duplicate records exist. In the case of duplicates, this
     * function will still "work", but in the sense of "delete first match".
     */
    int tagged_delete(const R &rec) {
        for (auto level : m_levels) {
            if (level && level->delete_record(rec)) {
                return 1;
            }
        }

        /*
         * If the record to be erased wasn't found, return 0. The
         * DynamicExtension itself will then search the active
         * Buffers.
         */
        return 0;
    }

    /*
     * Flush a buffer into the extension structure, performing any necessary
     * reconstructions to free up room in L0.
     *
     * FIXME: arguably, this should be a method attached to the buffer that
     * takes a structure as input.
     */
    inline bool flush_buffer(BuffView buffer) {
        state_vector tmp = m_current_state;

        if (tmp.size() == 0) {
            grow(tmp);
        }

        assert(can_reconstruct_with(0, buffer.get_record_count(), tmp));
        flush_buffer_into_l0(std::move(buffer));

        return true;
    }

    /*
     * Return the total number of records (including tombstones) within all
     * of the levels of the structure.
     */
    size_t get_record_count() {
        size_t cnt = 0;

        for (size_t i=0; i<m_levels.size(); i++) {
            if (m_levels[i]) cnt += m_levels[i]->get_record_count();
        }

        return cnt;
    }

    /*
     * Return the total number of tombstones contained within all of the
     * levels of the structure.
     */
    size_t get_tombstone_count() {
        size_t cnt = 0;

        for (size_t i=0; i<m_levels.size(); i++) {
            if (m_levels[i]) cnt += m_levels[i]->get_tombstone_count();
        }

        return cnt;
    }

    /*
     * Return the number of levels within the structure. Note that not
     * all of these levels are necessarily populated.
     */
    size_t get_height() {
        return m_levels.size();
    }

    /*
     * Return the amount of memory (in bytes) used by the shards within the
     * structure for storing the primary data structure and raw data.
     */
    size_t get_memory_usage() {
        size_t cnt = 0;
        for (size_t i=0; i<m_levels.size(); i++) {
            if (m_levels[i]) cnt += m_levels[i]->get_memory_usage();
        }

        return cnt;
    }

    /*
     * Return the amount of memory (in bytes) used by the shards within the
     * structure for storing auxiliary data structures. This total does not
     * include memory used for the main data structure, or raw data.
     */
    size_t get_aux_memory_usage() {
        size_t cnt = 0;
        for (size_t i=0; i<m_levels.size(); i++) {
            if (m_levels[i]) {
                cnt += m_levels[i]->get_aux_memory_usage();
            }
        }

        return cnt;
    }

    /*
     * Validate that no level in the structure exceeds its maximum tombstone
     * capacity. This is used to trigger preemptive compactions at the end of
     * the reconstruction process.
     */
    bool validate_tombstone_proportion() {
      long double ts_prop;
      for (size_t i = 0; i < m_levels.size(); i++) {
        if (m_levels[i]) {
          ts_prop = (long double)m_levels[i]->get_tombstone_count() /
                    (long double)calc_level_record_capacity(i);
          if (ts_prop > (long double)m_max_delete_prop) {
            return false;
          }
        }
      }

      return true;
    }

    bool validate_tombstone_proportion(level_index level) {
        long double ts_prop =  (long double) m_levels[level]->get_tombstone_count() / (long double) calc_level_record_capacity(level);
        return ts_prop <= (long double) m_max_delete_prop;
    }

    /*
     * Return a reference to the underlying vector of levels within the
     * structure.
     */
    std::vector<std::shared_ptr<InternalLevel<R, S, Q>>> &get_levels() {
        return m_levels;
    }

    /* 
     * NOTE: This cannot be simulated, because tombstone cancellation is not
     * cheaply predictable. It is possible that the worst case number could
     * be used instead, to allow for prediction, but compaction isn't a
     * major concern outside of sampling; at least for now. So I'm not
     * going to focus too much time on it at the moment.
     */
    ReconstructionVector get_compaction_tasks() {
        ReconstructionVector tasks;
        state_vector scratch_state = m_current_state;

        /* if the tombstone/delete invariant is satisfied, no need for compactions */
        if (validate_tombstone_proportion()) {
            return tasks;
        }

        /* locate the first level to violate the invariant */
        level_index violation_idx = -1;
        for (level_index i=0; i<m_levels.size(); i++) {
            if (!validate_tombstone_proportion(i))  {
                violation_idx = i;
                break;
            }
        }

        assert(violation_idx != -1);

        level_index base_level = find_reconstruction_target(violation_idx, scratch_state);
        if (base_level == -1) {
            base_level = grow(scratch_state);
        }

        for (level_index i=base_level; i>0; i--) {
            /*
             * The amount of storage required for the reconstruction accounts
             * for the cost of storing the new records, along with the
             * cost of retaining the old records during the process
             * (hence the 2x multiplier).
             *
             * FIXME: currently does not account for the *actual* size
             * of the shards, only the storage for the records
             * themselves.
             */
            size_t reccnt = m_levels[i - 1]->get_record_count();
            if constexpr (L == LayoutPolicy::LEVELING) {
                if (can_reconstruct_with(i, reccnt, scratch_state)) {
                    reccnt += m_levels[i]->get_record_count();
                }
            }
            tasks.add_reconstruction(i-i, i, reccnt);
        }

        return tasks;
    }

    /*
     *
     */
    ReconstructionVector get_reconstruction_tasks(size_t buffer_reccnt, 
                                                 state_vector scratch_state={}) {
        /* 
         * If no scratch state vector is provided, use a copy of the
         * current one. The only time an empty vector could be used as
         * *real* input to this function is when the current state is also
         * empty, so this should would even in that case.
         */
        if (scratch_state.size() == 0) {
            scratch_state = m_current_state;
        }

        ReconstructionVector reconstructions;
        size_t LOOKAHEAD = 1;
        for (size_t i=0; i<LOOKAHEAD; i++) {
            /*
             * If L0 cannot support a direct buffer flush, figure out what 
             * work must be done to free up space first. Otherwise, the
             * reconstruction vector will be initially empty.
             */
            if (!can_reconstruct_with(0, buffer_reccnt, scratch_state)) {
                auto local_recon = get_reconstruction_tasks_from_level(0, scratch_state);

                /* 
                 * for the first iteration, we need to do all of the
                 * reconstructions, so use these to initially the returned 
                 * reconstruction list
                 */
                if (i == 0) {
                    reconstructions = local_recon;
                    /*
                     * Quick sanity test of idea: if the next reconstruction
                     * would be larger than this one, steal the largest
                     * task from it and run it now instead.
                     */
                } else if (local_recon.get_total_reccnt() > reconstructions.get_total_reccnt()) {
                    auto t = local_recon.remove_reconstruction(0);
                    reconstructions.add_reconstruction(t);
                }
            }

            /* simulate the buffer flush in the scratch state */
            scratch_state[0].reccnt += buffer_reccnt;
            if (L == LayoutPolicy::TEIRING || scratch_state[0].shardcnt == 0) {
                scratch_state[0].shardcnt += 1;
            }

        }

        return std::move(reconstructions);
    }


    /*
     *
     */
    ReconstructionVector get_reconstruction_tasks_from_level(level_index source_level, state_vector &scratch_state) {
        ReconstructionVector reconstructions;

        /*
         * Find the first level capable of sustaining a reconstruction from
         * the level above it. If no such level exists, add a new one at
         * the bottom of the structure.
         */
        level_index base_level = find_reconstruction_target(source_level, scratch_state);
        if (base_level == -1) {
            base_level = grow(scratch_state);
        }

        /*
         * Determine the full set of reconstructions necessary to open up
         * space in the source level.
         */
        for (level_index i=base_level; i>source_level; i--) {
            size_t recon_reccnt = scratch_state[i-1].reccnt;
            size_t base_reccnt = recon_reccnt;

            /*
             * If using Leveling, the total reconstruction size will be the
             * records in *both* base and target, because they will need to
             * be merged (assuming that target isn't empty).
             */
            if constexpr (L == LayoutPolicy::LEVELING) {
                if (can_reconstruct_with(i, base_reccnt, scratch_state)) {
                    recon_reccnt += scratch_state[i].reccnt;
                }
            }
            reconstructions.add_reconstruction(i-1, i, recon_reccnt);

            /*
             * The base level will be emptied and its records moved to
             * the target.
             */
            scratch_state[i-1].reccnt = 0;
            scratch_state[i-1].shardcnt = 0;

            /*
             * The target level will have the records from the base level
             * added to it, and potentially gain a shard if the LayoutPolicy
             * is tiering or the level currently lacks any shards at all.
             */
            scratch_state[i].reccnt += base_reccnt;
            if (L == LayoutPolicy::TEIRING || scratch_state[i].shardcnt == 0) {
                scratch_state[i].shardcnt += 1;
            }
        }

        return std::move(reconstructions);
    }

    /*
     * Combine incoming_level with base_level and reconstruct the shard,
     * placing it in base_level. The two levels should be sequential--i.e. no
     * levels are skipped in the reconstruction process--otherwise the
     * tombstone ordering invariant may be violated.
     */
    inline void reconstruction(level_index base_level, level_index incoming_level) {
        size_t shard_capacity = (L == LayoutPolicy::LEVELING) ? 1 : m_scale_factor;

        if (base_level >= m_levels.size()) {
            m_levels.emplace_back(std::shared_ptr<InternalLevel<R, Shard, Q>>(new InternalLevel<R, Shard, Q>(base_level, shard_capacity)));

            m_current_state.push_back({0, calc_level_record_capacity(base_level), 
                                       0, shard_capacity});
        }

        if constexpr (L == LayoutPolicy::LEVELING) {
            /* if the base level has a shard, merge the base and incoming together to make a new one */
            if (m_levels[base_level]->get_shard_count() > 0) {
                m_levels[base_level] = InternalLevel<R, Shard, Q>::reconstruction(m_levels[base_level].get(), m_levels[incoming_level].get());
            /* otherwise, we can just move the incoming to the base */
            } else {
                m_levels[base_level] = m_levels[incoming_level];
            }

        } else {
            m_levels[base_level]->append_level(m_levels[incoming_level].get());
            m_levels[base_level]->finalize();
        }

        /* place a new, empty level where the incoming level used to be */
        m_levels[incoming_level] = std::shared_ptr<InternalLevel<R, Shard, Q>>(new InternalLevel<R, Shard, Q>(incoming_level, (L == LayoutPolicy::LEVELING) ? 1 : m_scale_factor));

        /* 
         * Update the state vector to match the *real* stage following
         * the reconstruction 
         */
        m_current_state[base_level] = {m_levels[base_level]->get_record_count(), 
            calc_level_record_capacity(base_level), m_levels[base_level]->get_shard_count(), shard_capacity};
        m_current_state[incoming_level] = {0, calc_level_record_capacity(incoming_level), 0, shard_capacity};
    }

    bool take_reference() {
        m_refcnt.fetch_add(1);
        return true;
    }

    bool release_reference() {
        assert(m_refcnt.load() > 0);
        m_refcnt.fetch_add(-1);
        return true;
    }

    size_t get_reference_count() {
        return m_refcnt.load();
    }

    std::vector<void *> get_query_states(std::vector<std::pair<ShardID, Shard*>> &shards, void *parms) {
        std::vector<void*> states;

        for (auto &level : m_levels) {
            level->get_query_states(shards, states, parms);
        }

        return states;
    }

private:
    size_t m_scale_factor;
    double m_max_delete_prop;
    size_t m_buffer_size;

    std::atomic<size_t> m_refcnt;

    std::vector<std::shared_ptr<InternalLevel<R, S, Q>>> m_levels;

    /* 
     * A pair of <record_count, shard_count> for each level in the
     * structure. Record counts may be slightly inaccurate due to
     * deletes.
     */
    state_vector m_current_state;

    /*
     * Add a new level to the scratch state and return its index.
     *
     * IMPORTANT: This does _not_ add a level to the extension structure
     * anymore. This is handled by the appropriate reconstruction and flush
     * methods as needed. This function is for use in "simulated"
     * reconstructions.
     */
    inline level_index grow(state_vector &scratch_state) {
        level_index new_idx = m_levels.size();
        size_t new_shard_cap = (L == LayoutPolicy::LEVELING) ? 1 : m_scale_factor;

        scratch_state.push_back({0, calc_level_record_capacity(new_idx), 
                                   0, new_shard_cap});
        return new_idx;
    }

    /*
     * Find the first level below the level indicated by idx that
     * is capable of sustaining a reconstruction and return its
     * level index. If no such level exists, returns -1. Also
     * returns -1 if idx==0, and no such level exists, to simplify
     * the logic of the first buffer flush.
     */
    inline level_index find_reconstruction_target(level_index idx, state_vector &state) {

        /* 
         * this handles the very first buffer flush, when the state vector
         * is empty.
         */
        if (idx == 0 && state.size() == 0) return -1;

        size_t incoming_rec_cnt = state[idx].reccnt;
        for (level_index i=idx+1; i<state.size(); i++) {
            if (can_reconstruct_with(i, incoming_rec_cnt, state)) {
                return i;
            }

            incoming_rec_cnt = state[idx].reccnt;
        }

        return -1;
    }

    inline void flush_buffer_into_l0(BuffView buffer) {
        size_t shard_capacity = (L == LayoutPolicy::LEVELING) ? 1 : m_scale_factor;

        if (m_levels.size() == 0) {
            m_levels.emplace_back(std::shared_ptr<InternalLevel<R, Shard, Q>>(new InternalLevel<R, Shard, Q>(0, shard_capacity)));

            m_current_state.push_back({0, calc_level_record_capacity(0), 
                                       0, shard_capacity});
        }

        if constexpr (L == LayoutPolicy::LEVELING) {
            // FIXME: Kludgey implementation due to interface constraints.
            auto old_level = m_levels[0].get();
            auto temp_level = new InternalLevel<R, Shard, Q>(0, 1);
            temp_level->append_buffer(std::move(buffer));

            if (old_level->get_shard_count() > 0) {
                m_levels[0] = InternalLevel<R, Shard, Q>::reconstruction(old_level, temp_level);
                delete temp_level;
            } else {
                m_levels[0] = std::shared_ptr<InternalLevel<R, Shard, Q>>(temp_level);
            }
        } else {
            m_levels[0]->append_buffer(std::move(buffer));
        }

        /* update the state vector */
        m_current_state[0].reccnt = m_levels[0]->get_record_count();
        m_current_state[0].shardcnt = m_levels[0]->get_shard_count(); 
    }

    /*
     * Mark a given memory level as no-longer in use by the tree. For now this
     * will just free the level. In future, this will be more complex as the
     * level may not be able to immediately be deleted, depending upon who
     * else is using it.
     */ 
    inline void mark_as_unused(std::shared_ptr<InternalLevel<R, Shard, Q>> level) {
        level.reset();
    }

    /*
     * Assume that level "0" should be larger than the buffer. The buffer
     * itself is index -1, which should return simply the buffer capacity.
     */
    inline size_t calc_level_record_capacity(level_index idx) {
        return m_buffer_size * pow(m_scale_factor, idx+1);
    }

    /*
     * Returns the number of records present on a specified level. 
     */
    inline size_t get_level_record_count(level_index idx) {
        return (m_levels[idx]) ? m_levels[idx]->get_record_count() : 0;
    }

    /*
     * Determines if a level can sustain a reconstruction with incoming_rec_cnt
     * additional records without exceeding its capacity.
     */
    inline bool can_reconstruct_with(level_index idx, size_t incoming_rec_cnt, state_vector &state) {
        if (idx >= state.size()) {
            return false;
        }

        if (L == LayoutPolicy::LEVELING) {
            return state[idx].reccnt + incoming_rec_cnt <= state[idx].reccap; 
        } else {
            return state[idx].shardcnt < state[idx].shardcap;
        }

        /* unreachable */
        assert(true);
    }
};

}


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