From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Wang Subject: Re: [PATCH v34 2/4] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT Date: Tue, 26 Jun 2018 20:27:44 +0800 Message-ID: <5B323140.1000306@intel.com> References: <1529928312-30500-1-git-send-email-wei.w.wang@intel.com> <1529928312-30500-3-git-send-email-wei.w.wang@intel.com> <20180626002822-mutt-send-email-mst@kernel.org> <5B31B71B.6080709@intel.com> <20180626064338-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180626064338-mutt-send-email-mst@kernel.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S. Tsirkin" Cc: yang.zhang.wz@gmail.com, virtio-dev@lists.oasis-open.org, riel@redhat.com, quan.xu0@gmail.com, kvm@vger.kernel.org, nilal@redhat.com, liliang.opensource@gmail.com, linux-kernel@vger.kernel.org, mhocko@kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, akpm@linux-foundation.org, virtualization@lists.linux-foundation.org, torvalds@linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org On 06/26/2018 11:56 AM, Michael S. Tsirkin wrote: > On Tue, Jun 26, 2018 at 11:46:35AM +0800, Wei Wang wrote: > >> >>> >>>> + if (!arrays) >>>> + return NULL; >>>> + >>>> + for (i = 0; i < max_array_num; i++) { >>> So we are getting a ton of memory here just to free it up a bit later. >>> Why doesn't get_from_free_page_list get the pages from free list for us? >>> We could also avoid the 1st allocation then - just build a list >>> of these. >> That wouldn't be a good choice for us. If we check how the regular >> allocation works, there are many many things we need to consider when pages >> are allocated to users. >> For example, we need to take care of the nr_free >> counter, we need to check the watermark and perform the related actions. >> Also the folks working on arch_alloc_page to monitor page allocation >> activities would get a surprise..if page allocation is allowed to work in >> this way. >> > mm/ code is well positioned to handle all this correctly. I'm afraid that would be a re-implementation of the alloc functions, and that would be much more complex than what we have. I think your idea of passing a list of pages is better. Best, Wei