src/platform/memory.cpp

// src/platform/memory.cpp - see include/strata/platform/memory.hpp.
#include "strata/platform/memory.hpp"

#if defined(_WIN32)
#define WIN32_LEAN_AND_MEAN
#define NOMINMAX
#include <windows.h>
#include <dxgi1_4.h>
#include <cstring>
#else
#include <sys/mman.h>
#include <unistd.h>
#endif

namespace strata::platform {

#if defined(_WIN32)
LockResult lock_resident(void* p, uint64_t bytes) {
    LockResult r;
    if (p == nullptr || bytes == 0) { r.note = "nothing to lock"; return r; }
    HANDLE self = GetCurrentProcess();
    SIZE_T min_ws = 0, max_ws = 0;
    DWORD flags = 0;
    if (!GetProcessWorkingSetSizeEx(self, &min_ws, &max_ws, &flags)) {
        r.note = "GetProcessWorkingSetSizeEx failed (error " + std::to_string(GetLastError()) + ")";
        return r;
    }
    // Locked pages count against the minimum working set, so it must grow by the region plus headroom for the
    // rest of the process. Soft limits: the maximum is not enforced, only the minimum is raised.
    const SIZE_T margin = (SIZE_T) 512 << 20;
    const SIZE_T new_min = min_ws + (SIZE_T) bytes + margin;
    const SIZE_T new_max = max_ws > new_min + margin ? max_ws : new_min + margin;
    if (!SetProcessWorkingSetSizeEx(self, new_min, new_max,
                                    QUOTA_LIMITS_HARDWS_MIN_DISABLE | QUOTA_LIMITS_HARDWS_MAX_DISABLE)) {
        r.note = "SetProcessWorkingSetSizeEx(" + std::to_string((unsigned long long) (new_min >> 20)) +
                 " MiB) failed (error " + std::to_string(GetLastError()) + ")";
        return r;
    }
    const uint64_t chunk = 1ull << 30;
    uint8_t* base = (uint8_t*) p;
    for (uint64_t off = 0; off < bytes; off += chunk) {
        const uint64_t n = bytes - off < chunk ? bytes - off : chunk;
        if (!VirtualLock(base + off, (SIZE_T) n)) {
            r.note = "VirtualLock stopped at " + std::to_string((unsigned long long) (off >> 20)) + " of " +
                     std::to_string((unsigned long long) (bytes >> 20)) + " MiB (error " +
                     std::to_string(GetLastError()) + ")";
            r.ok = off > 0;
            return r;
        }
        r.locked_bytes = off + n;
    }
    r.ok = true;
    r.note = "locked " + std::to_string((unsigned long long) (bytes >> 20)) + " MiB via working-set minimum + VirtualLock";
    return r;
}

void unlock_resident(void* p, uint64_t bytes) {
    if (p == nullptr || bytes == 0) return;
    const uint64_t chunk = 1ull << 30;
    for (uint64_t off = 0; off < bytes; off += chunk)
        VirtualUnlock((uint8_t*) p + off, (SIZE_T) (bytes - off < chunk ? bytes - off : chunk));
}

bool gpu_shared_memory_budget(const void* luid, uint64_t& budget, uint64_t& usage, std::string& why) {
    budget = usage = 0;
    // dxgi.dll is loaded when asked, not linked: a start that never needs this keeps the imports it had
    HMODULE dxgi = LoadLibraryA("dxgi.dll");
    if (dxgi == nullptr) { why = "dxgi.dll not found"; return false; }
    using CreateFactory = HRESULT(WINAPI*)(REFIID, void**);
    const auto create = (CreateFactory) (void*) GetProcAddress(dxgi, "CreateDXGIFactory1");
    IDXGIFactory1* factory = nullptr;
    if (create == nullptr || FAILED(create(__uuidof(IDXGIFactory1), (void**) &factory)) || factory == nullptr) {
        why = "CreateDXGIFactory1 failed";
        FreeLibrary(dxgi);
        return false;
    }
    bool ok = false;
    why = "no DXGI adapter has the CUDA device's LUID";
    for (UINT i = 0; !ok; ++i) {
        IDXGIAdapter1* a = nullptr;
        if (factory->EnumAdapters1(i, &a) == DXGI_ERROR_NOT_FOUND || a == nullptr) break;
        DXGI_ADAPTER_DESC1 d{};
        if (SUCCEEDED(a->GetDesc1(&d)) && std::memcmp(&d.AdapterLuid, luid, sizeof d.AdapterLuid) == 0) {
            IDXGIAdapter3* a3 = nullptr;
            DXGI_QUERY_VIDEO_MEMORY_INFO info{};
            if (SUCCEEDED(a->QueryInterface(__uuidof(IDXGIAdapter3), (void**) &a3)) && a3 != nullptr &&
                SUCCEEDED(a3->QueryVideoMemoryInfo(0, DXGI_MEMORY_SEGMENT_GROUP_NON_LOCAL, &info))) {
                budget = info.Budget;
                usage = info.CurrentUsage;
                ok = budget > 0;
                why = ok ? "" : "the adapter reports no shared-memory budget";
            } else {
                why = "QueryVideoMemoryInfo failed";
            }
            if (a3 != nullptr) a3->Release();
            a->Release();
            break;
        }
        a->Release();
    }
    factory->Release();
    FreeLibrary(dxgi);
    return ok;
}

uint64_t total_physical_memory() {
    MEMORYSTATUSEX ms{};
    ms.dwLength = sizeof ms;
    return GlobalMemoryStatusEx(&ms) ? (uint64_t) ms.ullTotalPhys : 0;
}
#else
LockResult lock_resident(void* p, uint64_t bytes) {
    LockResult r;
    if (p == nullptr || bytes == 0) { r.note = "nothing to lock"; return r; }
    if (mlock(p, bytes) != 0) { r.note = "mlock failed (raise ulimit -l)"; return r; }
    r.ok = true;
    r.locked_bytes = bytes;
    r.note = "mlock";
    return r;
}

void unlock_resident(void* p, uint64_t bytes) {
    if (p != nullptr && bytes != 0) munlock(p, bytes);
}

bool gpu_shared_memory_budget(const void*, uint64_t& budget, uint64_t& usage, std::string& why) {
    budget = usage = 0;
    why = "DXGI is Windows-only";
    return false;
}

uint64_t total_physical_memory() {
    const long pages = sysconf(_SC_PHYS_PAGES), page = sysconf(_SC_PAGE_SIZE);
    return pages > 0 && page > 0 ? (uint64_t) pages * (uint64_t) page : 0;
}
#endif

}  // namespace strata::platform