From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [PATCH] mm: disable `vm.max_map_count' sysctl limit Date: Mon, 27 Nov 2017 12:21:21 -0800 Message-ID: <20171127202121.GB3070@tassilo.jf.intel.com> References: <23066.59196.909026.689706@gargle.gargle.HOWL> <20171127101232.ykriowhatecnvjvg@dhcp22.suse.cz> <87vahv8whv.fsf@linux.intel.com> <20171127183218.33zm666jw3uqkxdq@dhcp22.suse.cz> <20171127195732.3hkfx57d3ytyccvp@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20171127195732.3hkfx57d3ytyccvp-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Michal Hocko Cc: Mikael Pettersson , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-api@vger.kernel.org On Mon, Nov 27, 2017 at 08:57:32PM +0100, Michal Hocko wrote: > On Mon 27-11-17 19:32:18, Michal Hocko wrote: > > On Mon 27-11-17 09:25:16, Andi Kleen wrote: > [...] > > > 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. -Andi