From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D8506C43142 for ; Wed, 27 Jun 2018 02:41:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7AF7626899 for ; Wed, 27 Jun 2018 02:41:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7AF7626899 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753155AbeF0Clo (ORCPT ); Tue, 26 Jun 2018 22:41:44 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:40750 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751682AbeF0Clm (ORCPT ); Tue, 26 Jun 2018 22:41:42 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1599E401B3AB; Wed, 27 Jun 2018 02:41:42 +0000 (UTC) Received: from redhat.com (ovpn-122-22.rdu2.redhat.com [10.10.122.22]) by smtp.corp.redhat.com (Postfix) with SMTP id 8BD1F1C66E; Wed, 27 Jun 2018 02:41:37 +0000 (UTC) Date: Wed, 27 Jun 2018 05:41:37 +0300 From: "Michael S. Tsirkin" 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 Subject: Re: [PATCH v34 2/4] virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT Message-ID: <20180627053952-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> <20180626163139-mutt-send-email-mst@kernel.org> <5B32E742.8080902@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5B32E742.8080902@intel.com> X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Wed, 27 Jun 2018 02:41:42 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Wed, 27 Jun 2018 02:41:42 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'mst@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 27, 2018 at 09:24:18AM +0800, Wei Wang wrote: > On 06/26/2018 09:34 PM, Michael S. Tsirkin wrote: > > 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? > > > > For every 2TB memory that the guest has, we allocate 4MB. Hmm I guess I'm missing something, I don't see it: + max_entries = max_free_page_blocks(ARRAY_ALLOC_ORDER); + entries_per_page = PAGE_SIZE / sizeof(__le64); + entries_per_array = entries_per_page * (1 << ARRAY_ALLOC_ORDER); + max_array_num = max_entries / entries_per_array + + !!(max_entries % entries_per_array); Looks like you always allocate the max number? > This is the same > for both cases. > For today's guests, usually there will be only one 4MB allocated and passed > to get_from_free_page_list. > > Best, > Wei > >