{inet,ipv6}_gro_receive functions perform flush checks (ttl, flags, iph->id, ...) against all packets in a loop. These flush checks are used in all merging UDP and TCP flows.
These checks need to be done only once and only against the found p skb, since they only affect flush and not same_flow.
This patch leverages correct network header offsets from the cb for both outer and inner network headers - allowing these checks to be done only once, in tcp_gro_receive and udp_gro_receive_segment. 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, thus removing the need for flush_id in napi_gro_cb.
This results in less parsing code for non-loop flush tests for TCP and UDP flows.
To make sure results are not within noise range - I've made netfilter drop all TCP packets, and measured CPU performance in GRO (in this case GRO is responsible for about 50% of the CPU utilization).
perf top while replaying 64 parallel IP/TCP streams merging in GRO: (gro_receive_network_flush is compiled inline to tcp_gro_receive) net-next: 6.94% [kernel] [k] inet_gro_receive 3.02% [kernel] [k] tcp_gro_receive
patch applied: 4.27% [kernel] [k] tcp_gro_receive 4.22% [kernel] [k] inet_gro_receive
perf top while replaying 64 parallel IP/IP/TCP streams merging in GRO (same results for any encapsulation, in this case inet_gro_receive is top offender in net-next) net-next: 10.09% [kernel] [k] inet_gro_receive 2.08% [kernel] [k] tcp_gro_receive
patch applied: 6.97% [kernel] [k] inet_gro_receive 3.68% [kernel] [k] tcp_gro_receive
Signed-off-by: Richard Gobert richardbgobert@gmail.com --- include/net/gro.h | 78 +++++++++++++++++++++++++++++++++++++----- net/core/gro.c | 3 -- net/ipv4/af_inet.c | 41 +--------------------- net/ipv4/tcp_offload.c | 17 ++------- net/ipv4/udp_offload.c | 10 ++---- net/ipv6/ip6_offload.c | 11 ------ 6 files changed, 76 insertions(+), 84 deletions(-)
diff --git a/include/net/gro.h b/include/net/gro.h index 3dafa0f31ae1..e0939b4b6579 100644 --- a/include/net/gro.h +++ b/include/net/gro.h @@ -36,15 +36,15 @@ 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 @@ -75,8 +75,8 @@ struct napi_gro_cb { /* 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 ipid_offset can be ignored */ + u8 ip_fixedid:1;
/* Number of gro_receive callbacks this packet already went through */ u8 recursion_counter:4; @@ -85,9 +85,6 @@ struct napi_gro_cb { u8 is_flist:1; );
- /* used to support CHECKSUM_COMPLETE for tunneling protocols */ - __wsum csum; - /* L3 offsets */ union { struct { @@ -442,6 +439,71 @@ static inline __wsum ip6_gro_compute_pseudo(const struct sk_buff *skb, skb_gro_len(skb), proto, 0)); }
+static inline int inet_gro_flush(const struct iphdr *iph, const struct iphdr *iph2, + struct sk_buff *p, bool outer) +{ + const u32 id = ntohl(*(__be32 *)&iph->id); + const u32 id2 = ntohl(*(__be32 *)&iph2->id); + const u16 ipid_offset = (id >> 16) - (id2 >> 16); + const u16 count = NAPI_GRO_CB(p)->count; + const u32 df = id & IP_DF; + int flush; + + /* All fields must match except length and checksum. */ + flush = (iph->ttl ^ iph2->ttl) | (iph->tos ^ iph2->tos) | (df ^ (id2 & IP_DF)); + + if (outer && df) + return flush; + + /* 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 (count == 1 && df && !ipid_offset) + NAPI_GRO_CB(p)->ip_fixedid = true; + + if (NAPI_GRO_CB(p)->ip_fixedid && df) + return flush | ipid_offset; + + return flush | (ipid_offset ^ count); +} + +static inline int ipv6_gro_flush(const struct ipv6hdr *iph, const 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 int __gro_receive_network_flush(const void *th, const void *th2, + struct sk_buff *p, const u16 diff, + bool outer) +{ + const void *nh = th - diff; + const void *nh2 = th2 - diff; + + if (((struct iphdr *)nh)->version == 6) + return ipv6_gro_flush(nh, nh2); + else + return inet_gro_flush(nh, nh2, p, outer); +} + +static inline int gro_receive_network_flush(const void *th, const void *th2, + struct sk_buff *p, int off) +{ + const bool encap_mark = NAPI_GRO_CB(p)->encap_mark; + int flush; + + flush = __gro_receive_network_flush(th, th2, p, off - NAPI_GRO_CB(p)->network_offset, encap_mark); + if (encap_mark) + flush |= __gro_receive_network_flush(th, th2, p, off - NAPI_GRO_CB(p)->inner_network_offset, false); + + return flush; +} + int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb);
/* Pass the currently batched GRO_NORMAL SKBs up to the stack. */ diff --git a/net/core/gro.c b/net/core/gro.c index 99a45a5211c9..3e9422c23bc9 100644 --- a/net/core/gro.c +++ b/net/core/gro.c @@ -331,8 +331,6 @@ 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; @@ -472,7 +470,6 @@ 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 428196e1541f..44564d009e95 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -1482,7 +1482,6 @@ struct sk_buff *inet_gro_receive(struct list_head *head, struct sk_buff *skb) struct sk_buff *p; unsigned int hlen; unsigned int off; - unsigned int id; int flush = 1; int proto;
@@ -1508,13 +1507,10 @@ struct sk_buff *inet_gro_receive(struct list_head *head, struct sk_buff *skb) goto out;
NAPI_GRO_CB(skb)->proto = proto; - id = ntohl(*(__be32 *)&iph->id); - flush = (u16)((ntohl(*(__be32 *)iph) ^ skb_gro_len(skb)) | (id & ~IP_DF)); - id >>= 16; + flush = (u16)((ntohl(*(__be32 *)iph) ^ skb_gro_len(skb)) | (ntohl(*(__be32 *)&iph->id) & ~IP_DF));
list_for_each_entry(p, head, list) { struct iphdr *iph2; - u16 flush_id;
if (!NAPI_GRO_CB(p)->same_flow) continue; @@ -1531,43 +1527,8 @@ 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; NAPI_GRO_CB(skb)->inner_network_offset = off;
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c index b70ae50e658d..5f0af1338d62 100644 --- a/net/ipv4/tcp_offload.c +++ b/net/ipv4/tcp_offload.c @@ -232,9 +232,7 @@ 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 |= (__force int)(flags & TCP_FLAG_CWR); + flush = (__force int)(flags & TCP_FLAG_CWR); flush |= (__force int)((flags ^ tcp_flag_word(th2)) & ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH)); flush |= (__force int)(th->ack_seq ^ th2->ack_seq); @@ -242,16 +240,7 @@ 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; + flush |= gro_receive_network_flush(th, th2, p, off);
mss = skb_shinfo(p)->gso_size;
@@ -338,7 +327,7 @@ INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff) iph->daddr, 0);
skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4 | - (NAPI_GRO_CB(skb)->is_atomic * SKB_GSO_TCP_FIXEDID); + (NAPI_GRO_CB(skb)->ip_fixedid * SKB_GSO_TCP_FIXEDID);
tcp_gro_complete(skb); return 0; diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c index 8721fe5beca2..726565159dc7 100644 --- a/net/ipv4/udp_offload.c +++ b/net/ipv4/udp_offload.c @@ -466,6 +466,7 @@ static struct sk_buff *udp_gro_receive_segment(struct list_head *head, struct sk_buff *skb) { struct udphdr *uh = udp_gro_udphdr(skb); + int off = skb_gro_offset(skb); struct sk_buff *pp = NULL; struct udphdr *uh2; struct sk_buff *p; @@ -505,14 +506,7 @@ static struct sk_buff *udp_gro_receive_segment(struct list_head *head, return p; }
- flush = NAPI_GRO_CB(p)->flush; - - 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; + flush = gro_receive_network_flush(uh, uh2, p, off);
/* Terminate the flow on len mismatch or if it grow "too much". * Under small packet flood GRO count could elsewhere grow a lot diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c index 288c7c6ea50f..bd5aff97d8b1 100644 --- a/net/ipv6/ip6_offload.c +++ b/net/ipv6/ip6_offload.c @@ -290,19 +290,8 @@ 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);