Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Eric Dumazet <> | Date | Thu, 25 Apr 2024 17:26:04 +0200 | Subject | Re: [PATCH v2 net-next v2 5/5] net: add heuristic for enabling TCP fraglist GRO |
| |
On Thu, Apr 25, 2024 at 5:04 PM Felix Fietkau <nbd@nbd.name> wrote: > > When forwarding TCP after GRO, software segmentation is very expensive, > especially when the checksum needs to be recalculated. > One case where that's currently unavoidable is when routing packets over > PPPoE. Performance improves significantly when using fraglist GRO > implemented in the same way as for UDP. > > When NETIF_F_GRO_FRAGLIST is enabled, perform a lookup for an established > socket in the same netns as the receiving device. While this may not > cover all relevant use cases in multi-netns configurations, it should be > good enough for most configurations that need this. > > Here's a measurement of running 2 TCP streams through a MediaTek MT7622 > device (2-core Cortex-A53), which runs NAT with flow offload enabled from > one ethernet port to PPPoE on another ethernet port + cake qdisc set to > 1Gbps. > > rx-gro-list off: 630 Mbit/s, CPU 35% idle > rx-gro-list on: 770 Mbit/s, CPU 40% idle > > Signe-off-by: Felix Fietkau <nbd@nbd.name> > --- > net/ipv4/tcp_offload.c | 48 +++++++++++++++++++++++++++++++++++++ > net/ipv6/tcpv6_offload.c | 51 ++++++++++++++++++++++++++++++++++++++++ > 2 files changed, 99 insertions(+) > > diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c > index 520fd425ab19..3bb96a110402 100644 > --- a/net/ipv4/tcp_offload.c > +++ b/net/ipv4/tcp_offload.c > @@ -405,6 +405,52 @@ void tcp_gro_complete(struct sk_buff *skb) > } > EXPORT_SYMBOL(tcp_gro_complete); > > +static void tcp4_check_fraglist_gro(struct list_head *head, struct sk_buff *skb) > +{ > + const struct iphdr *iph = skb_gro_network_header(skb);
I do not think loading iph before all skb_gro_header() and skb_gro_header_slow() calls is wise.
pskb_may_pull() can re-allocate skb->head
> + struct net *net = dev_net(skb->dev); > + unsigned int off, hlen, thlen; > + struct sk_buff *p; > + struct tcphdr *th; > + struct sock *sk; > + int iif, sdif; > + > + if (!(skb->dev->features & NETIF_F_GRO_FRAGLIST)) > + return; > + > + off = skb_gro_offset(skb); > + hlen = off + sizeof(*th); > + th = skb_gro_header(skb, hlen, off); > + if (unlikely(!th)) > + return; > + > + thlen = th->doff * 4; > + if (thlen < sizeof(*th)) > + return; > + > + hlen = off + thlen; > + if (!skb_gro_may_pull(skb, hlen)) { > + th = skb_gro_header_slow(skb, hlen, off); > + if (unlikely(!th)) > + return; > + } > + > + p = tcp_gro_lookup(head, th); > + if (p) { > + NAPI_GRO_CB(skb)->is_flist = NAPI_GRO_CB(p)->is_flist; > + return; > + } > + > + inet_get_iif_sdif(skb, &iif, &sdif); > + sk = __inet_lookup_established(net, net->ipv4.tcp_death_row.hashinfo, > + iph->saddr, th->source, > + iph->daddr, ntohs(th->dest), > + iif, sdif); > + NAPI_GRO_CB(skb)->is_flist = !sk; > + if (sk) > + sock_put(sk); > +} > + > INDIRECT_CALLABLE_SCOPE > struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb) > { > @@ -416,6 +462,8 @@ struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb) > return NULL; > } >
I would probably pull the whole TCP header here, before calling tcp4_check_fraglist_gro(head, skb) and no longer do this twice from tcp4_check_fraglist_gro() and tcp_gro_receive()
Perhaps define a new inline helper, that will be called from tcp4_gro_receive() and tcp6_gro_receive(), and not anymore from tcp_gro_receive()
static inline struct tcphdr *tcp_gro_pull_header(...) { .... off = skb_gro_offset(skb); hlen = off + sizeof(*th); th = skb_gro_header(skb, hlen, off); if (unlikely(!th)) return NULL;
thlen = th->doff * 4; if (thlen < sizeof(*th)) return NULL;
hlen = off + thlen; if (!skb_gro_may_pull(skb, hlen)) th = skb_gro_header_slow(skb, hlen, off);
return th; }
> + tcp4_check_fraglist_gro(head, skb); > + > return tcp_gro_receive(head, skb); > } > > diff --git a/net/ipv6/tcpv6_offload.c b/net/ipv6/tcpv6_offload.c > index c97d55cf036f..7948420dcad0 100644 > --- a/net/ipv6/tcpv6_offload.c > +++ b/net/ipv6/tcpv6_offload.c > @@ -7,12 +7,61 @@ > */ > #include <linux/indirect_call_wrapper.h> > #include <linux/skbuff.h> > +#include <net/inet6_hashtables.h> > #include <net/gro.h> > #include <net/protocol.h> > #include <net/tcp.h> > #include <net/ip6_checksum.h> > #include "ip6_offload.h" > > +static void tcp6_check_fraglist_gro(struct list_head *head, struct sk_buff *skb) > +{ > +#if IS_ENABLED(CONFIG_IPV6) > + const struct ipv6hdr *hdr = skb_gro_network_header(skb); > + struct net *net = dev_net(skb->dev); > + unsigned int off, hlen, thlen; > + struct sk_buff *p; > + struct tcphdr *th; > + struct sock *sk; > + int iif, sdif; > + > + if (!(skb->dev->features & NETIF_F_GRO_FRAGLIST)) > + return; > + > + off = skb_gro_offset(skb); > + hlen = off + sizeof(*th); > + th = skb_gro_header(skb, hlen, off); > + if (unlikely(!th)) > + return; > + > + thlen = th->doff * 4; > + if (thlen < sizeof(*th)) > + return; > + > + hlen = off + thlen; > + if (!skb_gro_may_pull(skb, hlen)) { > + th = skb_gro_header_slow(skb, hlen, off); > + if (unlikely(!th)) > + return; > + } > + > + p = tcp_gro_lookup(head, th); > + if (p) { > + NAPI_GRO_CB(skb)->is_flist = NAPI_GRO_CB(p)->is_flist; > + return; > + } > + > + inet6_get_iif_sdif(skb, &iif, &sdif); > + sk = __inet6_lookup_established(net, net->ipv4.tcp_death_row.hashinfo, > + &hdr->saddr, th->source, > + &hdr->daddr, ntohs(th->dest), > + iif, sdif); > + NAPI_GRO_CB(skb)->is_flist = !sk; > + if (sk) > + sock_put(sk); > +#endif /* IS_ENABLED(CONFIG_IPV6) */ > +} > + > INDIRECT_CALLABLE_SCOPE > struct sk_buff *tcp6_gro_receive(struct list_head *head, struct sk_buff *skb) > { > @@ -24,6 +73,8 @@ struct sk_buff *tcp6_gro_receive(struct list_head *head, struct sk_buff *skb) > return NULL; > } > > + tcp6_check_fraglist_gro(head, skb); > + > return tcp_gro_receive(head, skb); > } > > -- > 2.44.0 >
| ![\](/images/icornerr.gif) |