Re: [Qemu-devel] [PATCH RFC kernel] balloon: speed up inflating/deflating process

[Li, Liang Z]

> On 20/05/2016 11:59, Liang Li wrote:
> > +
> > +           sg_init_table(sg, 5);
> > +           sg_set_buf(&sg[0], &flags, sizeof(flags));
> > +           sg_set_buf(&sg[1], &start_pfn, sizeof(start_pfn));
> > +           sg_set_buf(&sg[2], &page_shift, sizeof(page_shift));
> > +           sg_set_buf(&sg[3], &bmap_len, sizeof(bmap_len));
> 
> These four should probably be placed in a single struct and therefore a single
> sg entry.  It might even be faster to place it together with the bitmap, thus
> avoiding the use of indirect descriptors.
> 

Yes, thanks for your suggestion.

> You should also test ballooning of a 64GB guest after filling in the page 
> cache,
> not just ballooning of a freshly booted 4GB guest.  This will give you a much
> more sparse bitmap.  Still, the improvement in sending PFNs to the host are

I will include the test result for that case in next version.


Thanks,

Liang

> impressive.
> 
> Thanks,
> 
> Paolo
> 
> > +           sg_set_buf(&sg[4], vb->page_bitmap +
> > +                            (start_pfn / BITS_PER_LONG), bmap_len);
> > +           virtqueue_add_outbuf(vq, sg, 5, vb, GFP_KERNEL);