Large OS pages support

Hi,
I'm trying to make snmalloc use large OS pages in my application. My use case has been mentioned in https://github.com/microsoft/snmalloc/issues/484#issuecomment-1073236187. My application is targeting Windows. It is memory bottlenecked and I want to reduce page faults. On Linux, 4KB pages can be merged into 2MB large pages implicitly and automatically, but on Windows large page allocation is explicit.

I have tried to modify the PAL to use large pages. The key modifications are:

static SNMALLOC_CONSTINIT_STATIC size_t minimum_alloc_size = 0x200000;    // 2MB
static constexpr size_t page_size = 0x200000;                             // 2MB

// in `notify_using`
void* r = VirtualAlloc(p, size, MEM_COMMIT | MEM_LARGE_PAGES, PAGE_READWRITE);

This PAL works well with snmalloc1, except the need of some small patches (alignas(OS_PAGE_SIZE) not possible, and need to check rsize > OS_PAGE_SIZE before rsize - OS_PAGE_SIZE). I don't know there are flaws or not but it can just run.

snmalloc2 cannot work with this PAL. It crashes at:
https://github.com/microsoft/snmalloc/blob/26324e8bfc28eda735a3335f83f3f1d8f21cc4a0/src/mem/corealloc.h#L690

I'm wondering whether I can use PAL to enable large os page support and expect snmalloc1 to work perfectly, and why this don't work with snmalloc2.

Sorry, may be duplicate with #222

Start by reviewing the PAL changes in commit 662e209a9528250e19f02a71e3b9cb5b3c7a5172 and the crash at src/mem/corealloc.h line 690. Compare the large-page behavior between snmalloc1 and snmalloc2, including the small patches noted in the issue. Done means documenting whether the PAL can support large pages reliably and why snmalloc2 fails.