[PATCH V2 net] ipv4:correct description for tcp_max_syn_backlog

[PATCH V2 net] ipv4:correct description for tcp_max_syn_backlog

[Weiping Pan]

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are out of date.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@gmail.com>
---
 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

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@gmail.com>
> ---
>  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@tuxdriver.com>

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

[David Miller]

From: Neil Horman <nhorman@tuxdriver.com>
Date: Tue, 6 Dec 2011 09:07:09 -0500

> 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@gmail.com>
 ...
> Acked-by: Neil Horman <nhorman@tuxdriver.com>

Applied, thanks everyone.