From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by kanga.kvack.org (Postfix) with ESMTP id 7A2626B0010 for ; Mon, 2 Jul 2018 08:20:06 -0400 (EDT) Received: by mail-ed1-f69.google.com with SMTP id x5-v6so1914844edh.8 for ; Mon, 02 Jul 2018 05:20:06 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id m5-v6si7483074edm.189.2018.07.02.05.20.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 02 Jul 2018 05:20:05 -0700 (PDT) Date: Mon, 2 Jul 2018 14:20:03 +0200 From: Michal Hocko Subject: Re: [RFC PATCH] mm, oom: distinguish blockable mode for mmu notifiers Message-ID: <20180702122003.GN19043@dhcp22.suse.cz> References: <20180622150242.16558-1-mhocko@kernel.org> <20180627074421.GF32348@dhcp22.suse.cz> <71f4184c-21ea-5af1-eeb6-bf7787614e2d@amd.com> <20180702115423.GK19043@dhcp22.suse.cz> <725cb1ad-01b0-42b5-56f0-c08c29804cb4@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <725cb1ad-01b0-42b5-56f0-c08c29804cb4@amd.com> Sender: owner-linux-mm@kvack.org List-ID: To: Christian =?iso-8859-1?Q?K=F6nig?= Cc: LKML , "David (ChunMing) Zhou" , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , Alex Deucher , David Airlie , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Doug Ledford , Jason Gunthorpe , Mike Marciniszyn , Dennis Dalessandro , Sudeep Dutt , Ashutosh Dixit , Dimitri Sivanich , Boris Ostrovsky , Juergen Gross , =?iso-8859-1?B?Suly9G1l?= Glisse , Andrea Arcangeli , kvm@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-rdma@vger.kernel.org, xen-devel@lists.xenproject.org, linux-mm@kvack.org, David Rientjes , Felix Kuehling On Mon 02-07-18 14:13:42, Christian Konig wrote: > Am 02.07.2018 um 13:54 schrieb Michal Hocko: > > On Mon 02-07-18 11:14:58, Christian Konig wrote: > > > Am 27.06.2018 um 09:44 schrieb Michal Hocko: > > > > This is the v2 of RFC based on the feedback I've received so far. The > > > > code even compiles as a bonus ;) I haven't runtime tested it yet, mostly > > > > because I have no idea how. > > > > > > > > Any further feedback is highly appreciated of course. > > > That sounds like it should work and at least the amdgpu changes now look > > > good to me on first glance. > > > > > > Can you split that up further in the usual way? E.g. adding the blockable > > > flag in one patch and fixing all implementations of the MMU notifier in > > > follow up patches. > > But such a code would be broken, no? Ignoring the blockable state will > > simply lead to lockups until the fixup parts get applied. > > Well to still be bisect-able you only need to get the interface change in > first with fixing the function signature of the implementations. That would only work if those functions return -AGAIN unconditionally. Otherwise they would pretend to not block while that would be obviously incorrect. This doesn't sound correct to me. > Then add all the new code to the implementations and last start to actually > use the new interface. > > That is a pattern we use regularly and I think it's good practice to do > this. But we do rely on the proper blockable handling. > > Is the split up really worth it? I was thinking about that but had hard > > times to end up with something that would be bisectable. Well, except > > for returning -EBUSY until all notifiers are implemented. Which I found > > confusing. > > It at least makes reviewing changes much easier, cause as driver maintainer > I can concentrate on the stuff only related to me. > > Additional to that when you cause some unrelated side effect in a driver we > can much easier pinpoint the actual change later on when the patch is > smaller. > > > > > > This way I'm pretty sure Felix and I can give an rb on the amdgpu/amdkfd > > > changes. > > If you are worried to give r-b only for those then this can be done even > > for larger patches. Just make your Reviewd-by more specific > > R-b: name # For BLA BLA > > Yeah, possible alternative but more work for me when I review it :) I definitely do not want to add more work to reviewers and I completely see how massive "flag days" like these are not popular but I really didn't find a reasonable way around that would be both correct and wouldn't add much more churn on the way. So if you really insist then I would really appreciate a hint on the way to achive the same without any above downsides. -- Michal Hocko SUSE Labs