Re: [PATCH net-next 2/2] net: airoha: Reorganize airoha_queue struct

Lorenzo Bianconi
2025-11-05T07:53:14Z

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> On Mon, 03 Nov 2025 11:27:56 +0100 Lorenzo Bianconi wrote:
> > Do not allocate memory for rx-only fields for hw tx queues and for tx-only
> > fields for hw rx queues.
>
> Could you share more details (pahole)
> Given that napi_struct is in the same struct, 20B is probably not going
> to make much difference?

I agree the difference is not huge, I added this patch mainly for code
readability. If you prefer I can drop the patch, I do not have a strong
opinion about it. What do you think?

net-next:

struct airoha_queue {
struct airoha_qdma * qdma; /* 0 8 */
spinlock_t lock; /* 8 4 */

/* XXX 4 bytes hole, try to pack */

struct airoha_queue_entry * entry; /* 16 8 */
struct airoha_qdma_desc * desc; /* 24 8 */
u16 head; /* 32 2 */
u16 tail; /* 34 2 */
int queued; /* 36 4 */
int ndesc; /* 40 4 */
int free_thr; /* 44 4 */
int buf_size; /* 48 4 */

/* XXX 4 bytes hole, try to pack */

struct napi_struct napi __attribute__((__aligned__(8))); /* 56 496 */

/* XXX last struct has 1 hole */

/* --- cacheline 8 boundary (512 bytes) was 40 bytes ago --- */
struct page_pool * page_pool; /* 552 8 */
struct sk_buff * skb; /* 560 8 */

/* size: 568, cachelines: 9, members: 13 */
/* sum members: 560, holes: 2, sum holes: 8 */
/* member types with holes: 1, total: 1 */
/* forced alignments: 1, forced holes: 1, sum forced holes: 4 */
/* last cacheline: 56 bytes */
} __attribute__((__aligned__(8)));

net-next + airoha_queue reorg:

struct airoha_queue {
struct airoha_qdma * qdma; /* 0 8 */
spinlock_t lock; /* 8 4 */

/* XXX 4 bytes hole, try to pack */

struct airoha_queue_entry * entry; /* 16 8 */
struct airoha_qdma_desc * desc; /* 24 8 */
int queued; /* 32 4 */
int ndesc; /* 36 4 */
struct napi_struct napi __attribute__((__aligned__(8))); /* 40 496 */

/* XXX last struct has 1 hole */

/* --- cacheline 8 boundary (512 bytes) was 24 bytes ago --- */
union {
struct {
u16 head; /* 536 2 */
u16 tail; /* 538 2 */
int buf_size; /* 540 4 */
struct page_pool * page_pool; /* 544 8 */
struct sk_buff * skb; /* 552 8 */
}; /* 536 24 */
struct {
struct list_head tx_list; /* 536 16 */
int free_thr; /* 552 4 */
}; /* 536 24 */
}; /* 536 24 */

/* size: 560, cachelines: 9, members: 8 */
/* sum members: 556, holes: 1, sum holes: 4 */
/* member types with holes: 1, total: 1 */
/* forced alignments: 1 */
/* last cacheline: 48 bytes */
} __attribute__((__aligned__(8)));

Regards,
Lorenzo

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