`total_memory_tracker.setOrRaiseHardLimit(...);` in `ConfigReloader` callback (see `Server.cpp`).
MemoryTracker::MemoryTracker(MemoryTracker * parent_, VariableContext level_) : parent(parent_), level(level_) {}
MemoryTracker::~MemoryTracker()
{
    if ((level == VariableContext::Process || level == VariableContext::User) && peak)
    {
        try
        {
            logPeakMemoryUsage();
        }
        catch (...)
        {
            
        }
    }
}
void MemoryTracker::logPeakMemoryUsage() const
{
    const auto * description = description_ptr.load(std::memory_order_relaxed);
    LOG_DEBUG(&Poco::Logger::get("MemoryTracker"),
        "Peak memory usage{}: {}.", (description ? " " + std::string(description) : ""), ReadableSize(peak));
}
void MemoryTracker::logMemoryUsage(Int64 current) const
{
    const auto * description = description_ptr.load(std::memory_order_relaxed);
    LOG_DEBUG(&Poco::Logger::get("MemoryTracker"),
        "Current memory usage{}: {}.", (description ? " " + std::string(description) : ""), ReadableSize(current));
}
void MemoryTracker::alloc(Int64 size)