SystemInterface

The SystemInterface module provides an abstraction over platform-specific system operations related to CPU affinity, thread priority, NUMA configuration, and file I/O. It serves as the foundation for CPU-level performance tuning and is primarily used by CpuAffinity and related components.

Purpose

Isolate system calls from platform-independent logic
Enable mocking and testing via NullSystemInterface
Provide unified access to thread and CPU-level control

Interface: `ISystemInterface`

Affinity

Method	Description
`setThreadAffinity(pthread_t thread, const std::vector<int>& cores)`	Pins a specific thread to the specified cores
`setCurrentThreadAffinity(const std::vector<int>& cores)`	Pins the current thread to the specified cores
`getCurrentThreadAffinity()`	Returns the current thread’s CPU affinity

Thread Priority

Method	Description
`setThreadPriority(pthread_t thread, int priority)`	Sets real-time priority (SCHED_FIFO) for a specific thread
`setCurrentThreadPriority(int priority)`	Sets real-time priority for the current thread

Topology & NUMA

Method	Description
`getNumCores()`	Returns the total number of logical CPU cores
`getIsolatedCores()`	Returns list of isolated cores from `isolcpus=` kernel argument
`getNumaNodes()`	Returns list of NUMA nodes and associated core IDs
`getNumaNodeForCore(int coreId)`	Returns NUMA node ID for the given core
`setMemoryPolicy(int nodeId)`	Sets preferred memory allocation policy for the current thread
`isNumaAvailable()`	Returns true if NUMA is supported and available

File I/O

Method	Description
`readFile(const std::string& path)`	Reads the content of a file
`writeFile(const std::string& path, const std::string& content)`	Writes content to a file

Implementations

`LinuxSystemInterface`

Linux-specific implementation based on:

sched_setaffinity, pthread_setschedparam, sched_setscheduler
NUMA support via <numa.h> and /sys/devices/system/node/
Parses /proc/cmdline for isolcpus=
Reads and writes files through std::ifstream / std::ofstream

`NullSystemInterface`

Dummy fallback used on unsupported platforms or in tests:

All methods return false or empty/default values
Safe no-op implementation

NUMA Support

NUMA is considered available if either:

The system links with libnuma and headers are present (FLOX_NUMA_LIBRARY_LINKED)
/sys/devices/system/node/ contains valid node* directories and cpulist files

Factory Function

std::unique_ptr<ISystemInterface> createSystemInterface();
````

Creates a platform-appropriate implementation:

* `LinuxSystemInterface` on Linux
* `NullSystemInterface` otherwise

## Example

```cpp
auto system = createSystemInterface();

if (system->isNumaAvailable()) {
  auto nodes = system->getNumaNodes();
  if (!nodes.empty()) {
    system->setCurrentThreadAffinity({nodes[0].second.front()});
    system->setMemoryPolicy(nodes[0].first);
  }
}

Integration

This interface is consumed by:

ThreadAffinity
CpuTopology
CoreAssignmentManager
CpuAffinity

It decouples platform-specific logic and enables system-aware optimization in a portable way.