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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED 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 0B224C43387 for ; Tue, 15 Jan 2019 01:00:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D49BB20578 for ; Tue, 15 Jan 2019 01:00:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727590AbfAOBAa (ORCPT ); Mon, 14 Jan 2019 20:00:30 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56364 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727389AbfAOBA3 (ORCPT ); Mon, 14 Jan 2019 20:00:29 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7E880811D3; Tue, 15 Jan 2019 01:00:29 +0000 (UTC) Received: from redhat.com (ovpn-124-229.rdu2.redhat.com [10.10.124.229]) by smtp.corp.redhat.com (Postfix) with SMTP id 3609E5D962; Tue, 15 Jan 2019 01:00:28 +0000 (UTC) Date: Mon, 14 Jan 2019 20:00:27 -0500 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, cohuck@redhat.com, borntraeger@de.ibm.com, pbonzini@redhat.com, dgilbert@redhat.com, pasic@linux.ibm.com Subject: Re: [PATCH v3 2/3] virtio-balloon: improve update_balloon_size_func Message-ID: <20190114195450-mutt-send-email-mst@kernel.org> References: <1546844466-38079-1-git-send-email-wei.w.wang@intel.com> <1546844466-38079-3-git-send-email-wei.w.wang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1546844466-38079-3-git-send-email-wei.w.wang@intel.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Tue, 15 Jan 2019 01:00:29 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 07, 2019 at 03:01:05PM +0800, Wei Wang wrote: > There is no need to update the balloon actual register when there is no > ballooning request. This patch avoids update_balloon_size when diff is 0. > > Signed-off-by: Wei Wang > Reviewed-by: Cornelia Huck > Reviewed-by: Halil Pasic It sounds reasonable but it does have a side effect of not writing into actual anymore. I am not sure actual never can get out of sync as a result. So better deferred, pls send this in the next merge window. > --- > drivers/virtio/virtio_balloon.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index fb12fe2..e33dc8e 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -457,9 +457,12 @@ static void update_balloon_size_func(struct work_struct *work) > update_balloon_size_work); > diff = towards_target(vb); > > + if (!diff) > + return; > + > if (diff > 0) > diff -= fill_balloon(vb, diff); > - else if (diff < 0) > + else > diff += leak_balloon(vb, -diff); > update_balloon_size(vb); > > -- > 2.7.4