@@ -29,46 +29,50 @@ struct napi_gro_cb {
/* Number of segments aggregated. */
u16 count;
- /* Start offset for remote checksum offload */
- u16 gro_remcsum_start;
+ /* Used in ipv6_gro_receive() and foo-over-udp */
+ u16 proto;
/* jiffies when first packet was created/queued */
unsigned long age;
- /* Used in ipv6_gro_receive() and foo-over-udp */
- u16 proto;
+ /* portion of the cb set to zero at every gro iteration */
+ struct_group(zeroed,
+
+ /* Start offset for remote checksum offload */
+ u16 gro_remcsum_start;
- /* This is non-zero if the packet may be of the same flow. */
- u8 same_flow:1;
+ /* This is non-zero if the packet may be of the same flow. */
+ u8 same_flow:1;
- /* Used in tunnel GRO receive */
- u8 encap_mark:1;
+ /* Used in tunnel GRO receive */
+ u8 encap_mark:1;
- /* GRO checksum is valid */
- u8 csum_valid:1;
+ /* GRO checksum is valid */
+ u8 csum_valid:1;
- /* Number of checksums via CHECKSUM_UNNECESSARY */
- u8 csum_cnt:3;
+ /* Number of checksums via CHECKSUM_UNNECESSARY */
+ u8 csum_cnt:3;
- /* Free the skb? */
- u8 free:2;
+ /* Free the skb? */
+ u8 free:2;
#define NAPI_GRO_FREE 1
#define NAPI_GRO_FREE_STOLEN_HEAD 2
- /* Used in foo-over-udp, set in udp[46]_gro_receive */
- u8 is_ipv6:1;
+ /* Used in foo-over-udp, set in udp[46]_gro_receive */
+ u8 is_ipv6:1;
- /* Used in GRE, set in fou/gue_gro_receive */
- u8 is_fou:1;
+ /* Used in GRE, set in fou/gue_gro_receive */
+ u8 is_fou:1;
- /* Used to determine if flush_id can be ignored */
- u8 is_atomic:1;
+ /* Used to determine if flush_id can be ignored */
+ u8 is_atomic:1;
- /* Number of gro_receive callbacks this packet already went through */
- u8 recursion_counter:4;
+ /* Number of gro_receive callbacks this packet already went through */
+ u8 recursion_counter:4;
- /* GRO is done by frag_list pointer chaining. */
- u8 is_flist:1;
+ /* GRO is done by frag_list pointer chaining. */
+ u8 is_flist:1;
+ );
/* used to support CHECKSUM_COMPLETE for tunneling protocols */
__wsum csum;
@@ -459,29 +459,22 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff
skb_set_network_header(skb, skb_gro_offset(skb));
skb_reset_mac_len(skb);
- NAPI_GRO_CB(skb)->same_flow = 0;
+ BUILD_BUG_ON(sizeof_field(struct napi_gro_cb, zeroed) != sizeof(u32));
+ BUILD_BUG_ON(!IS_ALIGNED(offsetof(struct napi_gro_cb, zeroed),
+ sizeof(u32))); /* Avoid slow unaligned acc */
+ *(u32 *)&NAPI_GRO_CB(skb)->zeroed = 0;
NAPI_GRO_CB(skb)->flush = skb_is_gso(skb) || skb_has_frag_list(skb);
- NAPI_GRO_CB(skb)->free = 0;
- NAPI_GRO_CB(skb)->encap_mark = 0;
- NAPI_GRO_CB(skb)->recursion_counter = 0;
- NAPI_GRO_CB(skb)->is_fou = 0;
NAPI_GRO_CB(skb)->is_atomic = 1;
- NAPI_GRO_CB(skb)->gro_remcsum_start = 0;
/* Setup for GRO checksum validation */
switch (skb->ip_summed) {
case CHECKSUM_COMPLETE:
NAPI_GRO_CB(skb)->csum = skb->csum;
NAPI_GRO_CB(skb)->csum_valid = 1;
- NAPI_GRO_CB(skb)->csum_cnt = 0;
break;
case CHECKSUM_UNNECESSARY:
NAPI_GRO_CB(skb)->csum_cnt = skb->csum_level + 1;
- NAPI_GRO_CB(skb)->csum_valid = 0;
break;
- default:
- NAPI_GRO_CB(skb)->csum_cnt = 0;
- NAPI_GRO_CB(skb)->csum_valid = 0;
}
pp = INDIRECT_CALL_INET(ptype->callbacks.gro_receive,
While inspecting some perf report, I noticed that the compiler emits suboptimal code for the napi CB initialization, fetching and storing multiple times the memory for flags bitfield. This is with gcc 10.3.1, but I observed the same with older compiler versions. We can help the compiler to do a nicer work clearing several fields at once using an u32 alias. The generated code is quite smaller, with the same number of conditional. Before: objdump -t net/core/gro.o | grep " F .text" 0000000000000bb0 l F .text 0000000000000357 dev_gro_receive After: 0000000000000bb0 l F .text 000000000000033c dev_gro_receive v1 -> v2: - use struct_group (Alexander and Alex) RFC -> v1: - use __struct_group to delimit the zeroed area (Alexander) Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- include/net/gro.h | 52 +++++++++++++++++++++++++---------------------- net/core/gro.c | 15 ++++---------- 2 files changed, 32 insertions(+), 35 deletions(-)