Function LargeBlockAlloc

library/cpp/lfalloc/lf_allocX64.h:451–491

static void* LargeBlockAlloc(size_t _nSize, ELFAllocCounter counter) {
    size_t pgCount = (_nSize + 4095) / 4096;
#ifdef _MSC_VER
    char* pRes = (char*)VirtualAlloc(0, (pgCount + 1) * 4096ll, MEM_COMMIT, PAGE_READWRITE);
    if (Y_UNLIKELY(pRes == 0)) {
        NMalloc::AbortFromCorruptedAllocator("out of memory");
    }
#else

    IncrementCounter(counter, pgCount * 4096ll);
    IncrementCounter(CT_SYSTEM_ALLOC, 4096ll);

    int lbHash = pgCount % LB_BUF_HASH;
    for (int i = 0; i < LB_BUF_SIZE; ++i) {
        void* p = lbFreePtrs[lbHash][i];
        if (p == nullptr)
            continue;
        if (DoCas(&lbFreePtrs[lbHash][i], (void*)nullptr, p) == p) {
            size_t realPageCount = TLargeBlk::As(p)->Pages;
            if (realPageCount == pgCount) {
                AtomicAdd(lbFreePageCount, -pgCount);
                TLargeBlk::As(p)->Mark(ELarge::Alloc);
                return p;
            } else {
                if (DoCas(&lbFreePtrs[lbHash][i], p, (void*)nullptr) != (void*)nullptr) {
                    // block was freed while we were busy
                    AtomicAdd(lbFreePageCount, -realPageCount);
                    LargeBlockUnmap(p, realPageCount);
                    --i;
                }
            }
        }
    }
    char* pRes = AllocWithMMap((pgCount + 1) * 4096ll, MM_HUGE);
#endif
    pRes += 4096ll;
    TLargeBlk::As(pRes)->SetSize(_nSize, pgCount);
    TLargeBlk::As(pRes)->Mark(ELarge::Alloc);

    return pRes;
}

#ifndef _MSC_VER
static void FreeAllLargeBlockMem() {