netdev - Re: [PATCH net-next] net: rps: Add the rfs_needed check when record flow hash

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Message-ID: <1495724103.6465.98.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Thu, 25 May 2017 07:55:03 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     gfree.wind@....163.com
Cc:     davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: rps: Add the rfs_needed check when record
 flow hash

On Wed, 2017-05-24 at 15:35 +0800, gfree.wind@....163.com wrote:
> From: Gao Feng <gfree.wind@....163.com>
> 
> There are two spots which invoke the sock_rps_record_flow_hash, one is
> sock_rps_record_flow which has already checked rfs_needed. But the other
> is tun_flow_update which doesn't check if the rfs is enabled.
> 
> Now rename the original function sock_rps_record_flow_hash to
> _sock_rps_record_flow_hash, and add one helper func which checks the
> rfs_needed.
> 
> The perf result of two functions is following.
> When rfs is disabled, it could enhance 58% performance with checking
> rfs_needed.
> When rfs is enabled, the performanc is lower than current about 29%.
> 
> Because the RFS is disabled by default. I think it is useful to tun
> driver.
> 
> The follow is test statistics.

> Signed-off-by: Gao Feng <gfree.wind@....163.com>
> ---
>  include/net/sock.h | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/include/net/sock.h b/include/net/sock.h
> index 3467d9e..584bb9a 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -910,7 +910,7 @@ static inline void sk_incoming_cpu_update(struct sock *sk)
>  	sk->sk_incoming_cpu = raw_smp_processor_id();
>  }
>  
> -static inline void sock_rps_record_flow_hash(__u32 hash)
> +static inline void _sock_rps_record_flow_hash(__u32 hash)
>  {
>  #ifdef CONFIG_RPS
>  	struct rps_sock_flow_table *sock_flow_table;
> @@ -922,6 +922,14 @@ static inline void sock_rps_record_flow_hash(__u32 hash)
>  #endif
>  }
>  
> +static inline void sock_rps_record_flow_hash(__u32 hash)
> +{
> +#ifdef CONFIG_RPS
> +	if (static_key_false(&rfs_needed))
> +		_sock_rps_record_flow_hash(hash);
> +#endif

Seems that after your patch, sock_rps_record_flow_hash() is no longer
needed/used.