WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] [PATCH] xen: increase static dmesg buffer to 64K

To: "Olaf Hering" <olaf@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] xen: increase static dmesg buffer to 64K
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Mon, 18 Jul 2011 08:30:03 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Mon, 18 Jul 2011 00:30:55 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <c6cade90d47f32e19f52.1310917403@xxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <c6cade90d47f32e19f52.1310917403@xxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
>>> On 17.07.11 at 17:43, Olaf Hering <olaf@xxxxxxxxx> wrote:
> # HG changeset patch
> # User Olaf Hering <olaf@xxxxxxxxx>
> # Date 1310917380 -7200
> # Node ID c6cade90d47f32e19f529930ba9f9acfa69f065f
> # Parent  31dd84463eece20bd01c7aee22b52a0c06c67545
> xen: increase static dmesg buffer to 64K
> 
> On large systems the static dmesg buffer will overflow the 16K buffer, early
> messages are lost. Increase the size to 64K to capture all lines on systems
> without serial console.

Please don't - on small systems it's a waste, and on even larger
systems it still won't help. If anything, the dynamic allocation may
need to happen earlier. As you probably saw, console_init_postirq()
already sizes the buffer dependent on the number of CPUs in the
system.

Additionally I think we greatly reduced the amount of per-CPU
messages printed by default. So one other thing to do would be to
look into completely suppressing all per-CPU messages by default if
these are still causing trouble.

Jan

> Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
> 
> diff -r 31dd84463eec -r c6cade90d47f xen/drivers/char/console.c
> --- a/xen/drivers/char/console.c
> +++ b/xen/drivers/char/console.c
> @@ -53,7 +53,7 @@ boolean_param("console_timestamps", opt_
>  static uint32_t __initdata opt_conring_size;
>  size_param("conring_size", opt_conring_size);
>  
> -#define _CONRING_SIZE 16384
> +#define _CONRING_SIZE (64 * 1024)
>  #define CONRING_IDX_MASK(i) ((i)&(conring_size-1))
>  static char __initdata _conring[_CONRING_SIZE];
>  static char *__read_mostly conring = _conring;
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx 
> http://lists.xensource.com/xen-devel 




_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel