From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752243AbeDTVV3 (ORCPT ); Fri, 20 Apr 2018 17:21:29 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:43552 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751228AbeDTVV1 (ORCPT ); Fri, 20 Apr 2018 17:21:27 -0400 Date: Fri, 20 Apr 2018 17:21:26 -0400 (EDT) From: Mikulas Patocka X-X-Sender: mpatocka@file01.intranet.prod.int.rdu2.redhat.com To: Matthew Wilcox cc: Michal Hocko , David Miller , Andrew Morton , linux-mm@kvack.org, eric.dumazet@gmail.com, edumazet@google.com, bhutchings@solarflare.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org, dm-devel@redhat.com, Vlastimil Babka Subject: Re: [PATCH] kvmalloc: always use vmalloc if CONFIG_DEBUG_VM In-Reply-To: <20180420210200.GH10788@bombadil.infradead.org> Message-ID: References: <3e65977e-53cd-bf09-bc4b-0ce40e9091fe@gmail.com> <20180418.134651.2225112489265654270.davem@davemloft.net> <20180420130852.GC16083@dhcp22.suse.cz> <20180420210200.GH10788@bombadil.infradead.org> User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 20 Apr 2018, Matthew Wilcox wrote: > On Fri, Apr 20, 2018 at 04:54:53PM -0400, Mikulas Patocka wrote: > > On Fri, 20 Apr 2018, Michal Hocko wrote: > > > No way. This is just wrong! First of all, you will explode most likely > > > on many allocations of small sizes. Second, CONFIG_DEBUG_VM tends to be > > > enabled quite often. > > > > You're an evil person who doesn't want to fix bugs. > > Steady on. There's no need for that. Michal isn't evil. Please > apologise. I see this attitude from Michal again and again. He didn't want to fix vmalloc(GFP_NOIO), he didn't want to fix alloc_pages sleeping when __GFP_NORETRY is used. So what should I say? Fix them and you won't be evil :-) (he could also fix the oom killer, so that it is triggered when free_memory+cache+free_swap goes beyond a threshold and not when you loop too long in the allocator) > > You refused to fix vmalloc(GFP_NOIO) misbehavior a year ago (did you make > > some progress with it since that time?) and you refuse to fix kvmalloc > > misuses. > > I understand you're frustrated, but this is not the way to get the problems > fixed. > > > I tried this patch on text-only virtual machine and /proc/vmallocinfo > > shows 614kB more memory. I tried it on a desktop machine with the chrome > > browser open and /proc/vmallocinfo space is increased by 7MB. So no - this > > won't exhaust memory and kill the machine. > > This is good data, thank you for providing it. > > > Arguing that this increases memory consumption is as bogus as arguing that > > CONFIG_LOCKDEP increses memory consumption. No one is forcing you to > > enable CONFIG_LOCKDEP and no one is forcing you to enable this kvmalloc > > test too. > > I think there's a real problem which is that CONFIG_DEBUG_VM is too broad. > It inserts code in a *lot* of places, some of which is quite expensive. > We would do better to split it into more granular pieces ... although > an explosion of configuration options isn't great either. Maybe just > CONFIG_DEBUG_VM and CONFIG_DEBUG_VM_EXPENSIVE. > > Michal may be wrong, but he's not evil. I already said that we can change it from CONFIG_DEBUG_VM to CONFIG_DEBUG_SG - or to whatever other option you may want, just to make sure that it is enabled in distro debug kernels by default. Mikulas