allocHugeExample.cpp

Go to the documentation of this file.

/**
 * @file
 * @copyright
 *   SPDX-FileCopyrightText: 2025-2025 European Southern Observatory (ESO)
 *
 *   SPDX-License-Identifier: LGPL-3.0-only
 */
#include <numapp/memory.hpp>
 
void Example() {
    // Allocate 16MiB from NUMA node 1 in 2MiB pages.
    auto const size = 16 * 1024 * 1024;
    auto const page_size = numapp::HugePagePreset::Huge2M;
 
    // 1) AllocateHuge will allocate size, rounding up to nearest page_size
    // multiple
    void* ptr = numapp::AllocateHuge(size,
                                     page_size,
                                     numapp::MemPolicy::MakeBindNode(1),
                                     numapp::MemPolicyFlag::Strict);
 
    // 2) It is particularly important to pre-fault huge-pages as the likelihood
    // for failure is higher. If page-fault would fail when memory is accessed
    // the result is a segmentation fault.
    if (auto ec = numapp::MemLock(ptr, size, numapp::LockFlag::PreFault); ec) {
        // Page-fault failed; this would have caused a segmentation fault if not
        // for `numapp::MemLock()`.
        throw std::system_error(ec, "Page fault failed");
    }
 
    // 3) FreeHuge will free memory, rounding up to nearest page_size multiple
    // as required by mmap.
    numapp::FreeHuge(ptr, size, page_size);
}