From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S937073AbdCJN0a (ORCPT ); Fri, 10 Mar 2017 08:26:30 -0500 Received: from mx1.redhat.com ([209.132.183.28]:3664 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933142AbdCJN0Y (ORCPT ); Fri, 10 Mar 2017 08:26:24 -0500 Subject: Re: [virtio-dev] Re: [PATCH v7 kernel 3/5] virtio-balloon: implementation of VIRTIO_BALLOON_F_CHUNK_TRANSFER To: Wei Wang , "Michael S. Tsirkin" References: <1488519630-89058-1-git-send-email-wei.w.wang@intel.com> <1488519630-89058-4-git-send-email-wei.w.wang@intel.com> <20170308054813-mutt-send-email-mst@kernel.org> <58C279B7.2060106@intel.com> Cc: "virtio-dev@lists.oasis-open.org" , "kvm@vger.kernel.org" , "qemu-devel@nongnu.org" , "linux-kernel@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "linux-mm@kvack.org" , Liang Li , Paolo Bonzini , Cornelia Huck , Amit Shah , "Hansen, Dave" , Andrea Arcangeli , Liang Li From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <2572fe97-4d28-fb34-4513-924959bc5cb2@redhat.com> Date: Fri, 10 Mar 2017 14:26:18 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <58C279B7.2060106@intel.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Fri, 10 Mar 2017 13:26:24 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 10.03.2017 um 11:02 schrieb Wei Wang: > On 03/08/2017 12:01 PM, Michael S. Tsirkin wrote: >> On Fri, Mar 03, 2017 at 01:40:28PM +0800, Wei Wang wrote: >>> From: Liang Li >>> >>> The implementation of the current virtio-balloon is not very >>> efficient, because the pages are transferred to the host one by one. >>> Here is the breakdown of the time in percentage spent on each >>> step of the balloon inflating process (inflating 7GB of an 8GB >>> idle guest). >>> >>> 1) allocating pages (6.5%) >>> 2) sending PFNs to host (68.3%) >>> 3) address translation (6.1%) >>> 4) madvise (19%) >>> >>> It takes about 4126ms for the inflating process to complete. >>> The above profiling shows that the bottlenecks are stage 2) >>> and stage 4). >>> >>> This patch optimizes step 2) by transfering pages to the host in >>> chunks. A chunk consists of guest physically continuous pages, and >>> it is offered to the host via a base PFN (i.e. the start PFN of >>> those physically continuous pages) and the size (i.e. the total >>> number of the pages). A normal chunk is formated as below: >>> ----------------------------------------------- >>> | Base (52 bit) | Size (12 bit)| >>> ----------------------------------------------- >>> For large size chunks, an extended chunk format is used: >>> ----------------------------------------------- >>> | Base (64 bit) | >>> ----------------------------------------------- >>> ----------------------------------------------- >>> | Size (64 bit) | >>> ----------------------------------------------- >>> >>> By doing so, step 4) can also be optimized by doing address >>> translation and madvise() in chunks rather than page by page. >>> >>> This optimization requires the negotation of a new feature bit, >>> VIRTIO_BALLOON_F_CHUNK_TRANSFER. >>> >>> With this new feature, the above ballooning process takes ~590ms >>> resulting in an improvement of ~85%. >>> >>> TODO: optimize stage 1) by allocating/freeing a chunk of pages >>> instead of a single page each time. >>> >>> Signed-off-by: Liang Li >>> Signed-off-by: Wei Wang >>> Suggested-by: Michael S. Tsirkin >>> Cc: Michael S. Tsirkin >>> Cc: Paolo Bonzini >>> Cc: Cornelia Huck >>> Cc: Amit Shah >>> Cc: Dave Hansen >>> Cc: Andrea Arcangeli >>> Cc: David Hildenbrand >>> Cc: Liang Li >>> Cc: Wei Wang >> Does this pass sparse? I see some endian-ness issues here. > > "pass sparse"- what does that mean? > I didn't see any complaints from "make" on my machine. https://kernel.org/doc/html/latest/dev-tools/sparse.html Static code analysis. You have to run it explicitly. -- Thanks, David