From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id A36096B0033 for ; Mon, 27 Nov 2017 13:32:23 -0500 (EST) Received: by mail-wm0-f69.google.com with SMTP id n8so11541912wmg.4 for ; Mon, 27 Nov 2017 10:32:23 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id w10si2184434edj.349.2017.11.27.10.32.20 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 27 Nov 2017 10:32:21 -0800 (PST) Date: Mon, 27 Nov 2017 19:32:18 +0100 From: Michal Hocko Subject: Re: [PATCH] mm: disable `vm.max_map_count' sysctl limit Message-ID: <20171127183218.33zm666jw3uqkxdq@dhcp22.suse.cz> References: <23066.59196.909026.689706@gargle.gargle.HOWL> <20171127101232.ykriowhatecnvjvg@dhcp22.suse.cz> <87vahv8whv.fsf@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87vahv8whv.fsf@linux.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andi Kleen Cc: Mikael Pettersson , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org On Mon 27-11-17 09:25:16, Andi Kleen wrote: > Michal Hocko writes: > > > > Could you be more explicit about _why_ we need to remove this tunable? > > I am not saying I disagree, the removal simplifies the code but I do not > > really see any justification here. > > It's an arbitrary scaling limit on the how many mappings the process > has. The more memory you have the bigger a problem it is. We've > ran into this problem too on larger systems. Why cannot you increase the limit? > 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. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org