From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH v3 2/3] virtio-balloon: improve update_balloon_size_func Date: Mon, 14 Jan 2019 20:00:27 -0500 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 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 To: Wei Wang Return-path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Content-Disposition: inline In-Reply-To: <1546844466-38079-3-git-send-email-wei.w.wang@intel.com> List-Id: kvm.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