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 1F1DD6B0003 for ; Tue, 26 Jun 2018 09:34:35 -0400 (EDT) Received: by mail-qt0-f199.google.com with SMTP id j11-v6so16504768qtf.15 for ; Tue, 26 Jun 2018 06:34:35 -0700 (PDT) Received: from mx1.redhat.com (mx3-rdu2.redhat.com. [66.187.233.73]) by mx.google.com with ESMTPS id g5-v6si1491656qtd.359.2018.06.26.06.34.34 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Jun 2018 06:34:34 -0700 (PDT) Date: Tue, 26 Jun 2018 16:34:27 +0300 From: "Michael S. Tsirkin" Subject: Re: [PATCH v34 2/4] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT Message-ID: <20180626163139-mutt-send-email-mst@kernel.org> 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> <5B323140.1000306@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5B323140.1000306@intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: Wei Wang Cc: virtio-dev@lists.oasis-open.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-mm@kvack.org, mhocko@kernel.org, akpm@linux-foundation.org, torvalds@linux-foundation.org, pbonzini@redhat.com, liliang.opensource@gmail.com, yang.zhang.wz@gmail.com, quan.xu0@gmail.com, nilal@redhat.com, riel@redhat.com, peterx@redhat.com On Tue, Jun 26, 2018 at 08:27:44PM +0800, Wei Wang wrote: > 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, A re-factoring - you can share code. The main difference is locking. > 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 How much memory is this allocating anyway? -- MST