Re: [Qemu-devel] [PATCH v14 3/5] virtio-balloon: VIRTIO_BALLOON_F_SG

[Michael S. Tsirkin]

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