chaos.hpp

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#pragma once

 
#include "scheduler_policy.hpp"
#include "thread_registry.hpp"
#include "thread_wrapper.hpp"
#include "topology.hpp"
#include <atomic>
#include <chrono>
#include <random>
#include <thread>
 
namespace threadschedule
{

struct ChaosConfig
{
    std::chrono::milliseconds interval{250};
    int priority_jitter{0}; // +/- jitter applied around current priority
    bool shuffle_affinity{true};
};
 
// RAII controller that periodically perturbs affinity/priority of registered threads matching a predicate
class ChaosController
{
  public:
    template <typename Predicate>
    ChaosController(ChaosConfig cfg, Predicate pred)
        : config_(cfg), stop_(false), worker_([this, pred]() { run_loop(pred); })
    {
    }
 
    ~ChaosController()
    {
        stop_ = true;
        if (worker_.joinable())
            worker_.join();
    }
 
    ChaosController(ChaosController const&) = delete;
    auto operator=(ChaosController const&) -> ChaosController& = delete;
 
  private:
    template <typename Predicate>
    void run_loop(Predicate pred)
    {
        std::mt19937 rng(std::random_device{}());
        while (!stop_)
        {
            registry().apply(pred, [&](RegisteredThreadInfo const& info) {
                auto blk = registry().get(info.tid);
                (void)blk;
            });
 
            // Affinity shuffle using topology
            if (config_.shuffle_affinity)
            {
                auto topo = read_topology();
                size_t idx = 0;
                registry().apply(pred, [&](RegisteredThreadInfo const& info) {
                    ThreadAffinity aff = affinity_for_node(
                        static_cast<int>(idx % (topo.numa_nodes > 0 ? topo.numa_nodes : 1)), static_cast<int>(idx));
                    (void)registry().set_affinity(info.tid, aff);
                    ++idx;
                });
            }
 
            // Priority jitter around current policy
            if (config_.priority_jitter != 0)
            {
                std::uniform_int_distribution<int> dist(-config_.priority_jitter, config_.priority_jitter);
                registry().apply(pred, [&](RegisteredThreadInfo const& info) {
                    int delta = dist(rng);
                    // Use normal as baseline if we can't read current
                    ThreadPriority prio = ThreadPriority::normal();
                    (void)registry().set_priority(info.tid, ThreadPriority{prio.value() + delta});
                });
            }
 
            std::this_thread::sleep_for(config_.interval);
        }
    }
 
    ChaosConfig config_;
    std::atomic<bool> stop_;
    std::thread worker_;
};
 
} // namespace threadschedule