Jungfraujoch/common/ThreadAffinity.h

// SPDX-FileCopyrightText: 2026 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
// SPDX-License-Identifier: GPL-3.0-only

#pragma once

#include <string>

// Keeping a GPU's worker threads on the socket the card hangs off, on a machine with more than one
// NUMA node, so the pinned host buffers they allocate and the copies to the card stay on that
// socket's memory controller and PCIe root. Read from /sys - no libnuma - and Linux only: elsewhere,
// and on a machine with a single node, every call is a no-op.

// The NUMA node of a PCI device, from its bus id as CUDA gives it ("0000:41:00.0"); -1 where it is
// not known or the machine has a single node.
int NumaNodeOfPciDevice(const std::string &pci_bus_id);

// Restrict the calling thread to the CPUs of `node` that the process may run on. Nothing happens for
// node < 0, or where that would leave the thread no CPU.
void PinThreadToNumaNode(int node);

// Give the calling thread back the CPUs the process started with. A thread inherits the affinity of
// the thread that creates it, so a thread pool first reached from a pinned worker would otherwise
// run every later parallel pass of the process on one socket.
void RestoreThreadAffinity();