Comment 63 for bug 1751460

(In reply to Michael Catanzaro from comment #4)
> Jeremy, here's some debug you could try adding to
> Source/bmalloc/bmalloc/VMAllocate.h:
>
> // At the top of the file, before the bmalloc namespace
> #include <cstring>
> #include <errno.h>
>
> inline void* tryVMAllocate(size_t vmSize)
> {
> vmValidate(vmSize);
> void* result = mmap(0, vmSize, PROT_READ | PROT_WRITE, MAP_PRIVATE |
> MAP_ANON | BMALLOC_NORESERVE, BMALLOC_VM_TAG, 0);
> if (result == MAP_FAILED)
> {
> WTFLogAlways("%s: mmap failed: %d (%s)", __FUNCTION__, errno,
> strerror(errno));
> return nullptr;
> }
> return result;
> }
>
> That would tell us which of the many possible errors are occurring here.
>
> And if you need an immediate workaround, you can of course build with
> -DUSE_SYSTEM_MALLOC=ON. That will be bad, so I can't recommend that... but
> you're already disabling GStreamerGL and web fonts.... :P

The immediate fix is disabling Gigacage by setting GIGACAGE_ENABLED 0 in bmalloc/Gigacage.h.
This keeps bmalloc, but disables Gigacage.

My guess is that Linux fails to mmap regions and returns MAP_FAILED if the size is very large.
But I'm not sure right now since it is working on my environment...
Anyway, @mcatanzaro, do you know the way to allocate virtual memory region which does not have actual backing pages?