Comment 67 for bug 1751460

(In reply to Michael Catanzaro from comment #8)
> One thing I just noticed, from
> https://bugzilla.gnome.org/show_bug.cgi?id=794056, is that this stack trace
> is exactly the same as the one valgrind hits when trying to use valgrind to
> debug epiphany since gigacage was enabled. That's probably expected, since
> valgrind attempts to allocate shadow bytes to keep track of the entire
> address space, which isn't practical under gigacage.

It sounds reasonable assumption to me.

>
> (In reply to Yusuke Suzuki from comment #6)
> > Anyway, @mcatanzaro, do you know the way to allocate virtual memory region
> > which does not have actual backing pages?
>
> I have no clue about this. I thought actual backing pages were only employed
> once the memory region is actually used.

(In reply to Michael Catanzaro from comment #9)
> (In reply to Yusuke Suzuki from comment #6)
> > My guess is that Linux fails to mmap regions and returns MAP_FAILED if the
> > size is very large.
>
> Keep in mind, we've had gigacage enabled and working fine for half a year....

Yeah, right. If it returns MAP_FAILED due to this issue, we should more constantly see this issue in our daily development. So my guess seems wrong.