Re: [PATCH 3/3] mm: catch memory commitment underflow

Andrew Morton
2014-06-25T22:03:21Z

On Wed, 25 Jun 2014 00:16:14 +0400 Konstantin Khlebnikov <koct9i@gmail.com> wrote:

> This patch prints warning (if CONFIG_DEBUG_VM=y) when
> memory commitment becomes too negative.
>
> ...
>
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -134,6 +134,12 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
> {
> unsigned long free, allowed, reserve;
>
> +#ifdef CONFIG_DEBUG_VM
> + WARN_ONCE(percpu_counter_read(&vm_committed_as) <
> + -(s64)vm_committed_as_batch * num_online_cpus(),
> + "memory commitment underflow");
> +#endif
> +
> vm_acct_memory(pages);

The changelog doesn't describe the reasons for making the change.

I assume this warning will detect the situation which the previous two
patches just fixed?