Re: [PATCH] mm: disable `vm.max_map_count' sysctl limit

On Mon 27-11-17 12:21:21, Andi Kleen wrote:

On Mon, Nov 27, 2017 at 08:57:32PM +0100, Michal Hocko wrote:

quoted

On Mon 27-11-17 19:32:18, Michal Hocko wrote:

quoted

On Mon 27-11-17 09:25:16, Andi Kleen wrote:

[...]

quoted

quoted

The reason the limit was there originally because it allows a DoS
attack against the kernel by filling all unswappable memory up with VMAs.

We can reduce the effect by accounting vmas to memory cgroups.

As it turned out we already do.
	vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT);

That only helps if you have memory cgroups enabled. It would be a regression
to break the accounting on all the systems that don't.

I agree. And I didn't say we should remove the existing limit. I am just
saying that we can reduce existing problems by increasing the limit and
relying on memcg accounting where possible.
-- 
Michal Hocko
SUSE Labs