> On 10/20/2016 11:24 PM, Liang Li wrote:
> > Add a new feature which supports sending the page information with a
> > bitmap. The current implementation uses PFNs array, which is not very
> > efficient. Using bitmap can improve the performance of
> > inflating/deflating significantly
>
> Why is it not efficient? How is using a bitmap more efficient? What kinds of
> cases is the bitmap inefficient?
>
> > The page bitmap header will used to tell the host some information
> > about the page bitmap. e.g. the page size, page bitmap length and
> > start pfn.
>
> Why did you choose to add these features to the structure? What benefits
> do they add?
>
> Could you describe your solution a bit here, and describe its strengths and
> weaknesses?
>
Will elaborate the solution in V4.
> > /* Size of a PFN in the balloon interface. */ #define
> > VIRTIO_BALLOON_PFN_SHIFT 12 @@ -82,4 +83,22 @@ struct
> > virtio_balloon_stat {
> > __virtio64 val;
> > } __attribute__((packed));
> >
> > +/* Page bitmap header structure */
> > +struct balloon_bmap_hdr {
> > + /* Used to distinguish different request */
> > + __virtio16 cmd;
> > + /* Shift width of page in the bitmap */
> > + __virtio16 page_shift;
> > + /* flag used to identify different status */
> > + __virtio16 flag;
> > + /* Reserved */
> > + __virtio16 reserved;
> > + /* ID of the request */
> > + __virtio64 req_id;
> > + /* The pfn of 0 bit in the bitmap */
> > + __virtio64 start_pfn;
> > + /* The length of the bitmap, in bytes */
> > + __virtio64 bmap_len;
> > +};
>
> FWIW this is totally unreadable. Please do something like this:
>
> > +struct balloon_bmap_hdr {
> > + __virtio16 cmd; /* Used to distinguish different ...
> > + __virtio16 page_shift; /* Shift width of page in the bitmap */
> > + __virtio16 flag; /* flag used to identify different...
> > + __virtio16 reserved; /* Reserved */
> > + __virtio64 req_id; /* ID of the request */
> > + __virtio64 start_pfn; /* The pfn of 0 bit in the bitmap */
> > + __virtio64 bmap_len; /* The length of the bitmap, in bytes */
> > +};
>
> and please make an effort to add useful comments. "/* Reserved */"
> seems like a waste of bytes to me.
OK. Maybe 'padding' is better than 'reserved' .
Thanks for your comments!
Liang
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