Method allocImpl

src/Common/MemoryTracker.cpp:161–284

void MemoryTracker::allocImpl(Int64 size, bool throw_if_memory_exceeded)
{
    if (size < 0)
        throw DB::Exception(DB::ErrorCodes::LOGICAL_ERROR, "Negative size ({}) is passed to MemoryTracker. It is a bug.", size);

    if (BlockerInThread::isBlocked(level))
    {
        /// Since the BlockerInThread should respect the level, we should go to the next parent.
        if (auto * loaded_next = parent.load(std::memory_order_relaxed))
            loaded_next->allocImpl(size, throw_if_memory_exceeded);
        return;
    }

    /** Using memory_order_relaxed means that if allocations are done simultaneously,
      *  we allow exception about memory limit exceeded to be thrown only on next allocation.
      * So, we allow over-allocations.
      */
    Int64 will_be = size + amount.fetch_add(size, std::memory_order_relaxed);

    auto metric_loaded = metric.load(std::memory_order_relaxed);
    if (metric_loaded != CurrentMetrics::end())
        CurrentMetrics::add(metric_loaded, size);

    Int64 current_hard_limit = hard_limit.load(std::memory_order_relaxed);
    Int64 current_profiler_limit = profiler_limit.load(std::memory_order_relaxed);

    /// Cap the limit to the total_memory_tracker, since it may include some drift
    /// for user-level memory tracker.
    ///
    /// And since total_memory_tracker is reset to the process resident
    /// memory peridically (in AsynchronousMetrics::update()), any limit can be
    /// capped to it, to avoid possible drift.
    if (unlikely(current_hard_limit
        && will_be > current_hard_limit
        && level == VariableContext::User))
    {
        Int64 total_amount = total_memory_tracker.get();
        if (amount > total_amount)
        {
            set(total_amount);
            will_be = size + total_amount;
        }
    }

#ifdef MEMORY_TRACKER_DEBUG_CHECKS
    if (unlikely(memory_tracker_always_throw_logical_error_on_allocation))
    {
        memory_tracker_always_throw_logical_error_on_allocation = false;
        throw DB::Exception(DB::ErrorCodes::LOGICAL_ERROR, "Memory tracker: allocations not allowed.");
    }
#endif

    std::bernoulli_distribution fault(fault_probability);
    if (unlikely(fault_probability && fault(thread_local_rng)) && throw_if_memory_exceeded && memoryTrackerCanThrow(level, true))
    {
        ProfileEvents::increment(ProfileEvents::QueryMemoryLimitExceeded);
        amount.fetch_sub(size, std::memory_order_relaxed);