From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f199.google.com (mail-qt0-f199.google.com [209.85.216.199]) by kanga.kvack.org (Postfix) with ESMTP id 1AA876B0292 for ; Tue, 20 Jun 2017 14:17:38 -0400 (EDT) Received: by mail-qt0-f199.google.com with SMTP id m57so84374409qta.9 for ; Tue, 20 Jun 2017 11:17:38 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id 138si240560qkh.173.2017.06.20.11.17.36 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 20 Jun 2017 11:17:37 -0700 (PDT) Date: Tue, 20 Jun 2017 21:17:26 +0300 From: "Michael S. Tsirkin" Subject: Re: [PATCH v11 4/6] mm: function to offer a page block on the free list Message-ID: <20170620211445-mutt-send-email-mst@kernel.org> References: <1497004901-30593-1-git-send-email-wei.w.wang@intel.com> <1497004901-30593-5-git-send-email-wei.w.wang@intel.com> <1497977049.20270.100.camel@redhat.com> <7b626551-6d1b-c8d5-4ef7-e357399e78dc@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7b626551-6d1b-c8d5-4ef7-e357399e78dc@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: David Hildenbrand Cc: Rik van Riel , Dave Hansen , Wei Wang , linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, cornelia.huck@de.ibm.com, akpm@linux-foundation.org, mgorman@techsingularity.net, aarcange@redhat.com, amit.shah@redhat.com, pbonzini@redhat.com, liliang.opensource@gmail.com, Nitesh Narayan Lal On Tue, Jun 20, 2017 at 06:49:33PM +0200, David Hildenbrand wrote: > On 20.06.2017 18:44, Rik van Riel wrote: > > On Mon, 2017-06-12 at 07:10 -0700, Dave Hansen wrote: > > > >> The hypervisor is going to throw away the contents of these pages, > >> right? As soon as the spinlock is released, someone can allocate a > >> page, and put good data in it. What keeps the hypervisor from > >> throwing > >> away good data? > > > > That looks like it may be the wrong API, then? > > > > We already have hooks called arch_free_page and > > arch_alloc_page in the VM, which are called when > > pages are freed, and allocated, respectively. > > > > Nitesh Lal (on the CC list) is working on a way > > to efficiently batch recently freed pages for > > free page hinting to the hypervisor. > > > > If that is done efficiently enough (eg. with > > MADV_FREE on the hypervisor side for lazy freeing, > > and lazy later re-use of the pages), do we still > > need the harder to use batch interface from this > > patch? > > > David's opinion incoming: > > No, I think proper free page hinting would be the optimum solution, if > done right. This would avoid the batch interface and even turn > virtio-balloon in some sense useless. I agree generally. But we have to balance that against the fact that this was discussed since at least 2011 and no one built this solution yet. > -- > > Thanks, > > David -- 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