> > +struct qed_ll2_tx_pkt_info {
> > + u8 num_of_bds;
> > + u16 vlan;
> > + u8 bd_flags;
> > + u16 l4_hdr_offset_w; /* from start of packet */
> > + enum qed_ll2_tx_dest tx_dest;
> > + enum qed_ll2_roce_flavor_type qed_roce_flavor;
> > + dma_addr_t first_frag;
> > + u16 first_frag_len;
> > + bool enable_ip_cksum;
> > + bool enable_l4_cksum;
> > + bool calc_ip_len;
> > + void *cookie;
> > +};
> > +
>
> This layout is extremely inefficient, with lots of padding in between struct
> members.
>
> Group small u8 members and u16 members together so that they consume
> full 32-bit areas so you can eliminate all of the padding.
While I can mend the holes, the total structure size doesn't really change:
struct qed_ll2_tx_pkt_info {
u8 num_of_bds; /* 0 1 */
/* XXX 1 byte hole, try to pack */
u16 vlan; /* 2 2 */
u8 bd_flags; /* 4 1 */
/* XXX 1 byte hole, try to pack */
u16 l4_hdr_offset_w; /* 6 2 */
enum qed_ll2_tx_dest tx_dest; /* 8 4 */
enum qed_ll2_roce_flavor_type qed_roce_flavor; /* 12 4 */
dma_addr_t first_frag; /* 16 8 */
u16 first_frag_len; /* 24 2 */
bool enable_ip_cksum; /* 26 1 */
bool enable_l4_cksum; /* 27 1 */
bool calc_ip_len; /* 28 1 */
/* XXX 3 bytes hole, try to pack */
void * cookie; /* 32 8 */
/* size: 40, cachelines: 1, members: 12 */
/* sum members: 35, holes: 3, sum holes: 5 */
/* last cacheline: 40 bytes */
};
Becomes:
struct qed_ll2_tx_pkt_info {
void * cookie; /* 0 8 */
dma_addr_t first_frag; /* 8 8 */
enum qed_ll2_tx_dest tx_dest; /* 16 4 */
enum qed_ll2_roce_flavor_type qed_roce_flavor; /* 20 4 */
u16 vlan; /* 24 2 */
u16 l4_hdr_offset_w; /* 26 2 */
u16 first_frag_len; /* 28 2 */
u8 num_of_bds; /* 30 1 */
u8 bd_flags; /* 31 1 */
bool enable_ip_cksum; /* 32 1 */
bool enable_l4_cksum; /* 33 1 */
bool calc_ip_len; /* 34 1 */
/* size: 40, cachelines: 1, members: 12 */
/* padding: 5 */
/* last cacheline: 40 bytes */
};
I'm going to send the changed version in V2 as as there's no harm to it,
[+ we *can* reduce the size of qed_ll2_comp_rx_data you commented
for patch #2 in series]
But one thing I thought of asking - do we consider layouts of relatively
insignificant structures to be some golden coding standard?
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