Re: [PATCH V2 net] ipv4:correct description for tcp_max_syn_backlog

[Neil Horman]

On Tue, Dec 06, 2011 at 03:39:41PM +0800, Weiping Pan wrote:
> Since commit c5ed63d66f24(tcp: fix three tcp sysctls tuning),
> sysctl_max_syn_backlog is determined by tcp_hashinfo->ehash_mask,
> and the minimal value is 128, and it will increase in proportion to the
> memory of machine.
> The original description for tcp_max_syn_backlog and sysctl_max_syn_backlog
> are out of date.
> 
> Changelog:
> V2: update description for sysctl_max_syn_backlog
> 
> Signed-off-by: Weiping Pan <panweiping3@xxxxxxxxx>
> ---
>  Documentation/networking/ip-sysctl.txt |   10 +++++-----
>  net/core/request_sock.c                |    7 ++++---
>  2 files changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
> index f049a1c..589f2da 100644
> --- a/Documentation/networking/ip-sysctl.txt
> +++ b/Documentation/networking/ip-sysctl.txt
> @@ -282,11 +282,11 @@ tcp_max_ssthresh - INTEGER
>  	Default: 0 (off)
>  
>  tcp_max_syn_backlog - INTEGER
> -	Maximal number of remembered connection requests, which are
> -	still did not receive an acknowledgment from connecting client.
> -	Default value is 1024 for systems with more than 128Mb of memory,
> -	and 128 for low memory machines. If server suffers of overload,
> -	try to increase this number.
> +	Maximal number of remembered connection requests, which have not
> +	received an acknowledgment from connecting client.
> +	The minimal value is 128 for low memory machines, and it will
> +	increase in proportion to the memory of machine.
> +	If server suffers from overload, try increasing this number.
>  
>  tcp_max_tw_buckets - INTEGER
>  	Maximal number of timewait sockets held by system simultaneously.
> diff --git a/net/core/request_sock.c b/net/core/request_sock.c
> index 182236b..9b570a6 100644
> --- a/net/core/request_sock.c
> +++ b/net/core/request_sock.c
> @@ -26,10 +26,11 @@
>   * but then some measure against one socket starving all other sockets
>   * would be needed.
>   *
> - * It was 128 by default. Experiments with real servers show, that
> + * The minimum value of it is 128. Experiments with real servers show that
>   * it is absolutely not enough even at 100conn/sec. 256 cures most
> - * of problems. This value is adjusted to 128 for very small machines
> - * (<=32Mb of memory) and to 1024 on normal or better ones (>=256Mb).
> + * of problems.
> + * This value is adjusted to 128 for low memory machines,
> + * and it will increase in proportion to the memory of machine.
>   * Note : Dont forget somaxconn that may limit backlog too.
>   */
>  int sysctl_max_syn_backlog = 256;
> -- 
> 1.7.4.4
> 
> 
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>

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