Re: [PATCH v9 1/8] hugetlb_cgroup: Add hugetlb_cgroup reservation counter

[Mina Almasry]

> >> On 12/17/19 3:16 PM, Mina Almasry wrote:
> >
> > The design we went with based on previous discussions is as follows:
> > hugetlb pages faulted without a prior reservation get accounted at
> > fault time, rather than reservation time, and if the fault causes the
> > counter to cross the limit, the charge fails, hence the fault fails,
> > hence the process gets sigbus'd.
>
> Ok, sorry I did not recall the design discussion.
>

No worries! It has indeed been a while since that discussion.

> > This means that one counter I'm adding here can cover both use cases:
> > if the userspace uses MAP_NORESERVE, then their memory is accounted at
> > fault time and they may get sigbus'd.
>
> Let's make sure this is clearly documented.  Someone could be surprised
> if their application not using reserves gets a SIGBUS because there is a
> reserve limit.

I have some stuff on that already in the docs patch, but I'll beef
that section up to ensure there is no confusion.