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List:       linux-virtualization
Subject:    Re: [PATCH v14 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG
From:       "Michael S. Tsirkin" <mst () redhat ! com>
Date:       2017-08-21 20:22:17
Message-ID: 20170821232052-mutt-send-email-mst () kernel ! org
[Download RAW message or body]

On Fri, Aug 18, 2017 at 03:39:27PM +0800, Wei Wang wrote:
> On 08/18/2017 10:22 AM, Michael S. Tsirkin wrote:
> > +static void send_balloon_page_sg(struct virtio_balloon *vb,
> > +				 struct virtqueue *vq,
> > +				 void *addr,
> > +				 uint32_t size)
> > +{
> > +	unsigned int len;
> > +	int ret;
> > +
> > +	do {
> > +		ret = add_one_sg(vq, addr, size);
> > +		virtqueue_kick(vq);
> > +		wait_event(vb->acked, virtqueue_get_buf(vq, &len));
> > +		/*
> > +		 * It is uncommon to see the vq is full, because the sg is sent
> > +		 * one by one and the device is able to handle it in time. But
> > +		 * if that happens, we go back to retry after an entry gets
> > +		 * released.
> > +		 */
> > Why send one by one though? Why not batch some s/gs and wait for all
> > of them to be completed? If memory if fragmented, waiting every time is
> > worse than what we have now (VIRTIO_BALLOON_ARRAY_PFNS_MAX at a time).
> > 
> 
> OK, I'll do batching in some fashion.
> 
> 
> Best,
> Wei
> 
> 

btw you need to address the build errors that kbot has found.

-- 
MST
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