{inet,ipv6}_gro_receive functions perform flush checks (ttl, flags, iph->id, ...) against all packets in a loop. These flush checks are relevant only to tcp flows, and as such they're used to determine whether the packets can be merged later in tcp_gro_receive.
These checks are not relevant to UDP packets. Furthermore, they need to be done only once in tcp_gro_receive and only against the found p skb, since they only affect flush and not same_flow.
Leveraging the initial commit in the series, correct network header offsets are saved for both outer and inner network headers - allowing these checks to be done only once, in tcp_gro_receive. As a result, NAPI_GRO_CB(p)->flush is not used at all. In addition - flush_id checks are more declarative and contained in inet_gro_flush_id, thus removing the need for flush_id in napi_gro_cb.
This results in less parsing code for UDP flows and non-loop flush tests for TCP flows.
For example, running 64 IP/UDP netperf connections: ./super_netperf.sh 64 -H 1.1.1.2 -t UDP_STREAM -l 120
Running perf top for 90s we can see that relatively less time is spent on inet_gro_receive:
net-next:
Samples: 330K of event 'cycles:P', 4000 Hz, Event count (approx.): 45945660156 lost: 0/0 drop: 0/0 1.43% [kernel] [k] inet_gro_receive
patch applied:
Samples: 295K of event 'cycles:P', 4000 Hz, Event count (approx.): 44726408099 lost: 0/0 drop: 0/0 1.22% [kernel] [k] inet_gro_receive
Signed-off-by: Richard Gobert richardbgobert@gmail.com --- include/net/gro.h | 9 ++---- net/core/gro.c | 3 -- net/ipv4/af_inet.c | 36 --------------------- net/ipv4/tcp_offload.c | 71 ++++++++++++++++++++++++++++++++++-------- net/ipv6/ip6_offload.c | 11 ------- 5 files changed, 61 insertions(+), 69 deletions(-)
diff --git a/include/net/gro.h b/include/net/gro.h index 89502a7e35ed..e6db591cdc32 100644 --- a/include/net/gro.h +++ b/include/net/gro.h @@ -35,15 +35,15 @@ struct napi_gro_cb { /* This is non-zero if the packet cannot be merged with the new skb. */ u16 flush;
- /* Save the IP ID here and check when we get to the transport layer */ - u16 flush_id; - /* Number of segments aggregated. */ u16 count;
/* Used in ipv6_gro_receive() and foo-over-udp and esp-in-udp */ u16 proto;
+ /* used to support CHECKSUM_COMPLETE for tunneling protocols */ + __wsum csum; + /* Used in napi_gro_cb::free */ #define NAPI_GRO_FREE 1 #define NAPI_GRO_FREE_STOLEN_HEAD 2 @@ -83,9 +83,6 @@ struct napi_gro_cb { /* GRO is done by frag_list pointer chaining. */ u8 is_flist:1; ); - - /* used to support CHECKSUM_COMPLETE for tunneling protocols */ - __wsum csum; };
#define NAPI_GRO_CB(skb) ((struct napi_gro_cb *)(skb)->cb) diff --git a/net/core/gro.c b/net/core/gro.c index 0759277dc14e..b7dced5bcef7 100644 --- a/net/core/gro.c +++ b/net/core/gro.c @@ -332,8 +332,6 @@ static void gro_list_prepare(const struct list_head *head, list_for_each_entry(p, head, list) { unsigned long diffs;
- NAPI_GRO_CB(p)->flush = 0; - if (hash != skb_get_hash_raw(p)) { NAPI_GRO_CB(p)->same_flow = 0; continue; @@ -466,7 +464,6 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff sizeof(u32))); /* Avoid slow unaligned acc */ *(u32 *)&NAPI_GRO_CB(skb)->zeroed = 0; NAPI_GRO_CB(skb)->flush = skb_has_frag_list(skb); - NAPI_GRO_CB(skb)->is_atomic = 1; NAPI_GRO_CB(skb)->count = 1; if (unlikely(skb_is_gso(skb))) { NAPI_GRO_CB(skb)->count = skb_shinfo(skb)->gso_segs; diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index c0f3c162bf73..fd7378ecc4e3 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -1509,7 +1509,6 @@ struct sk_buff *inet_gro_receive(struct list_head *head, struct sk_buff *skb)
list_for_each_entry(p, head, list) { struct iphdr *iph2; - u16 flush_id;
if (!NAPI_GRO_CB(p)->same_flow) continue; @@ -1526,43 +1525,8 @@ struct sk_buff *inet_gro_receive(struct list_head *head, struct sk_buff *skb) NAPI_GRO_CB(p)->same_flow = 0; continue; } - - /* All fields must match except length and checksum. */ - NAPI_GRO_CB(p)->flush |= - (iph->ttl ^ iph2->ttl) | - (iph->tos ^ iph2->tos) | - ((iph->frag_off ^ iph2->frag_off) & htons(IP_DF)); - - NAPI_GRO_CB(p)->flush |= flush; - - /* We need to store of the IP ID check to be included later - * when we can verify that this packet does in fact belong - * to a given flow. - */ - flush_id = (u16)(id - ntohs(iph2->id)); - - /* This bit of code makes it much easier for us to identify - * the cases where we are doing atomic vs non-atomic IP ID - * checks. Specifically an atomic check can return IP ID - * values 0 - 0xFFFF, while a non-atomic check can only - * return 0 or 0xFFFF. - */ - if (!NAPI_GRO_CB(p)->is_atomic || - !(iph->frag_off & htons(IP_DF))) { - flush_id ^= NAPI_GRO_CB(p)->count; - flush_id = flush_id ? 0xFFFF : 0; - } - - /* If the previous IP ID value was based on an atomic - * datagram we can overwrite the value and ignore it. - */ - if (NAPI_GRO_CB(skb)->is_atomic) - NAPI_GRO_CB(p)->flush_id = flush_id; - else - NAPI_GRO_CB(p)->flush_id |= flush_id; }
- NAPI_GRO_CB(skb)->is_atomic = !!(iph->frag_off & htons(IP_DF)); NAPI_GRO_CB(skb)->flush |= flush; if (NAPI_GRO_CB(skb)->encap_mark) skb_set_inner_network_header(skb, off); diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c index 8bbcd3f502ac..962c1b900e11 100644 --- a/net/ipv4/tcp_offload.c +++ b/net/ipv4/tcp_offload.c @@ -178,6 +178,60 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb, return segs; }
+static inline bool inet_gro_flush(struct iphdr *iph, struct iphdr *iph2) +{ + /* All fields must match except length and checksum. */ + return (iph->ttl ^ iph2->ttl) | + (iph->tos ^ iph2->tos) | + ((iph->frag_off ^ iph2->frag_off) & htons(IP_DF)); +} + +static inline bool ipv6_gro_flush(struct ipv6hdr *iph, struct ipv6hdr *iph2) +{ + /* Version:4<Traffic_Class:8><Flow_Label:20> */ + __be32 first_word = *(__be32 *)iph ^ *(__be32 *)iph2; + + /* Flush if Traffic Class fields are different. */ + return (first_word & htonl(0x0FF00000)) | + (__force __be32)(iph->hop_limit ^ iph2->hop_limit); +} + +static inline bool inet_gro_flush_id(struct sk_buff *p, struct iphdr *iph, + struct iphdr *iph2) +{ + u16 flush_id = ntohs(iph->id) - ntohs(iph2->id); + u16 is_atomic = !!(iph->frag_off & htons(IP_DF)); + u16 count_masked; + + /* When we receive our second frame we can make a decision on if we + * continue this flow as an atomic flow with a fixed ID or if we use + * an incrementing ID. + */ + if (NAPI_GRO_CB(p)->count == 1) + NAPI_GRO_CB(p)->is_atomic = flush_id == 0; + + /* Ignore outer IP ID value if based on atomic datagram. */ + if (NAPI_GRO_CB(p)->encap_mark && is_atomic && iph2 == ip_hdr(p)) + return false; + + is_atomic &= NAPI_GRO_CB(p)->is_atomic; + count_masked = NAPI_GRO_CB(p)->count & ~(-is_atomic | is_atomic); + + return flush_id ^ count_masked; +} + +static bool tcp_gro_network_flush(struct sk_buff *p, struct sk_buff *skb, + int offset) +{ + void *nh = (NAPI_GRO_CB(skb)->frag0 ?: skb->data) + offset; + void *nh2 = p->data + offset; + + if (((struct iphdr *)nh)->version == 6) + return ipv6_gro_flush(nh, nh2); + + return inet_gro_flush(nh, nh2) | inet_gro_flush_id(p, nh, nh2); +} + struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb) { struct sk_buff *pp = NULL; @@ -232,8 +286,10 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb) goto out_check_final;
found: - /* Include the IP ID check below from the inner most IP hdr */ - flush = NAPI_GRO_CB(p)->flush; + flush = tcp_gro_network_flush(p, skb, skb_network_offset(skb)); + if (NAPI_GRO_CB(skb)->encap_mark) + flush |= tcp_gro_network_flush(p, skb, skb_inner_network_offset(skb)); + flush |= (__force int)(flags & TCP_FLAG_CWR); flush |= (__force int)((flags ^ tcp_flag_word(th2)) & ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH)); @@ -242,17 +298,6 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb) flush |= *(u32 *)((u8 *)th + i) ^ *(u32 *)((u8 *)th2 + i);
- /* When we receive our second frame we can made a decision on if we - * continue this flow as an atomic flow with a fixed ID or if we use - * an incrementing ID. - */ - if (NAPI_GRO_CB(p)->flush_id != 1 || - NAPI_GRO_CB(p)->count != 1 || - !NAPI_GRO_CB(p)->is_atomic) - flush |= NAPI_GRO_CB(p)->flush_id; - else - NAPI_GRO_CB(p)->is_atomic = false; - mss = skb_shinfo(p)->gso_size;
/* If skb is a GRO packet, make sure its gso_size matches prior packet mss. diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c index db7e3db587b9..8bf93a0e9669 100644 --- a/net/ipv6/ip6_offload.c +++ b/net/ipv6/ip6_offload.c @@ -291,19 +291,8 @@ INDIRECT_CALLABLE_SCOPE struct sk_buff *ipv6_gro_receive(struct list_head *head, nlen - sizeof(struct ipv6hdr))) goto not_same_flow; } - /* flush if Traffic Class fields are different */ - NAPI_GRO_CB(p)->flush |= !!((first_word & htonl(0x0FF00000)) | - (__force __be32)(iph->hop_limit ^ iph2->hop_limit)); - NAPI_GRO_CB(p)->flush |= flush; - - /* If the previous IP ID value was based on an atomic - * datagram we can overwrite the value and ignore it. - */ - if (NAPI_GRO_CB(skb)->is_atomic) - NAPI_GRO_CB(p)->flush_id = 0; }
- NAPI_GRO_CB(skb)->is_atomic = true; NAPI_GRO_CB(skb)->flush |= flush;
skb_gro_postpull_rcsum(skb, iph, nlen);