linux-kernel - Re: -27% netperf TCP_STREAM regression by "tcp_memcontrol: Kill struct tcp

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Message-ID: <1382533364.7572.15.camel@edumazet-glaptop.roam.corp.google.com>
Date:	Wed, 23 Oct 2013 06:02:44 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Christoph Paasch <christoph.paasch@...ouvain.be>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	David Miller <davem@...emloft.net>, fengguang.wu@...el.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: -27% netperf TCP_STREAM regression by "tcp_memcontrol: Kill
 struct tcp_memcontrol"

On Wed, 2013-10-23 at 14:25 +0200, Christoph Paasch wrote:

> may it be the below?
> 
> 
> Cheers,
> Christoph
> 
> ----
> From: Christoph Paasch <christoph.paasch@...ouvain.be>
> Subject: [PATCH] Fix: Dereference pointer-value of sk_prot->memory_pressure
> 
> 2e685cad57 (tcp_memcontrol: Kill struct tcp_memcontrol) falsly modified
> the access to memory_pressure of sk->sk_prot->memory_pressure. The patch
> did modify the memory_pressure-field of struct cg_proto, but not the one
> of struct proto.
> 
> So, the access to sk_prot->memory_pressure should not be changed.
> 
> Reported-by: Fengguang Wu <fengguang.wu@...el.com>
> Signed-off-by: Christoph Paasch <christoph.paasch@...ouvain.be>
> ---
>  include/net/sock.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/net/sock.h b/include/net/sock.h
> index c93542f..e3a18ff 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -1137,7 +1137,7 @@ static inline bool sk_under_memory_pressure(const struct sock *sk)
>         if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
>                 return !!sk->sk_cgrp->memory_pressure;
> 
> -       return !!sk->sk_prot->memory_pressure;
> +       return !!*sk->sk_prot->memory_pressure;
>  }
> 
>  static inline void sk_leave_memory_pressure(struct sock *sk)

Nice catch, thanks !

Acked-by: Eric Dumazet <edumazet@...gle.com>



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