Hi,
On Mon, 2017-12-18 at 12:11 +0800, zhangliping wrote:
> From: zhangliping <zhanglipin...@baidu.com>
>
> Under our udp pressure performance test, after gro is disabled, rx rate
> will be improved from ~2500kpps to ~2800kpps. We can find some difference
> from perf report:
> 1. gro is enabled:
> 24.23% [kernel] [k] udp4_lib_lookup2
> 5.42% [kernel] [k] __memcpy
> 3.87% [kernel] [k] fib_table_lookup
> 3.76% [kernel] [k] __netif_receive_skb_core
> 3.68% [kernel] [k] ip_rcv
>
> 2. gro is disabled:
> 9.66% [kernel] [k] udp4_lib_lookup2
> 9.47% [kernel] [k] __memcpy
> 4.75% [kernel] [k] fib_table_lookup
> 4.71% [kernel] [k] __netif_receive_skb_core
> 3.90% [kernel] [k] virtnet_poll
>
> So if there's no udp tunnel(such as vxlan) configured, we can skip
> the udp gro processing.
I tested something similar some time ago, but I measured a much smaller
gain. Also the topmost perf offenders looks quite different from what I
see here, can you please share more details about the test case?
> Signed-off-by: zhangliping <zhanglipin...@baidu.com>
> ---
> include/net/udp.h | 2 ++
> net/ipv4/udp_offload.c | 7 +++++++
> net/ipv4/udp_tunnel.c | 11 ++++++++++-
> 3 files changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/include/net/udp.h b/include/net/udp.h
> index 6c759c8594e2..c503f8b06845 100644
> --- a/include/net/udp.h
> +++ b/include/net/udp.h
> @@ -188,6 +188,8 @@ static inline struct udphdr *udp_gro_udphdr(struct
> sk_buff *skb)
> return uh;
> }
>
> +extern struct static_key_false udp_gro_needed;
> +
> /* hash routines shared between UDPv4/6 and UDP-Litev4/6 */
> static inline int udp_lib_hash(struct sock *sk)
> {
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index 01801b77bd0d..9cb11a833964 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -10,10 +10,14 @@
> * UDPv4 GSO support
> */
>
> +#include <linux/static_key.h>
> #include <linux/skbuff.h>
> #include <net/udp.h>
> #include <net/protocol.h>
>
> +DEFINE_STATIC_KEY_FALSE(udp_gro_needed);
> +EXPORT_SYMBOL_GPL(udp_gro_needed);
> +
I think that adding a new static key is not required, as we can
probably reuse 'udp_encap_needed' and 'udpv6_encap_needed'. The latter
choice allows earlier branching (in
udp4_gro_receive()/udp6_gro_receive() instead of udp_gro_receive().
Cheers,
Paolo
