From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id 4BD9C6B000A for ; Thu, 12 Jul 2018 07:30:19 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id g20-v6so18385558pfi.2 for ; Thu, 12 Jul 2018 04:30:19 -0700 (PDT) Received: from mga18.intel.com (mga18.intel.com. [134.134.136.126]) by mx.google.com with ESMTPS id f200-v6si23506363pfa.164.2018.07.12.04.30.18 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 12 Jul 2018 04:30:18 -0700 (PDT) Message-ID: <5B473CB8.1050306@intel.com> Date: Thu, 12 Jul 2018 19:34:16 +0800 From: Wei Wang MIME-Version: 1.0 Subject: Re: [PATCH v35 1/5] mm: support to get hints of free page blocks References: <1531215067-35472-1-git-send-email-wei.w.wang@intel.com> <1531215067-35472-2-git-send-email-wei.w.wang@intel.com> <5B455D50.90902@intel.com> <20180711092152.GE20050@dhcp22.suse.cz> <5B46BB46.2080802@intel.com> <5B46C258.40601@intel.com> <20180712081317.GD32648@dhcp22.suse.cz> In-Reply-To: <20180712081317.GD32648@dhcp22.suse.cz> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Linus Torvalds , virtio-dev@lists.oasis-open.org, Linux Kernel Mailing List , virtualization , KVM list , linux-mm , "Michael S. Tsirkin" , Andrew Morton , Paolo Bonzini , liliang.opensource@gmail.com, yang.zhang.wz@gmail.com, quan.xu0@gmail.com, nilal@redhat.com, Rik van Riel , peterx@redhat.com On 07/12/2018 04:13 PM, Michal Hocko wrote: > On Thu 12-07-18 10:52:08, Wei Wang wrote: >> On 07/12/2018 10:30 AM, Linus Torvalds wrote: >>> On Wed, Jul 11, 2018 at 7:17 PM Wei Wang wrote: >>>> Would it be better to remove __GFP_THISNODE? We actually want to get all >>>> the guest free pages (from all the nodes). >>> Maybe. Or maybe it would be better to have the memory balloon logic be >>> per-node? Maybe you don't want to remove too much memory from one >>> node? I think it's one of those "play with it" things. >>> >>> I don't think that's the big issue, actually. I think the real issue >>> is how to react quickly and gracefully to "oops, I'm trying to give >>> memory away, but now the guest wants it back" while you're in the >>> middle of trying to create that 2TB list of pages. >> OK. virtio-balloon has already registered an oom notifier >> (virtballoon_oom_notify). I plan to add some control there. If oom happens, >> - stop the page allocation; >> - immediately give back the allocated pages to mm. > Please don't. Oom notifier is an absolutely hideous interface which > should go away sooner or later (I would much rather like the former) so > do not build a new logic on top of it. I would appreciate if you > actually remove the notifier much more. > > You can give memory back from the standard shrinker interface. If we are > reaching low reclaim priorities then we are struggling to reclaim memory > and then you can start returning pages back. OK. Just curious why oom notifier is thought to be hideous, and has it been a consensus? Best, Wei