linux-kernel - Re: [PATCH] Inhibit NMI watchdog when Alt-SysRq-T operation is underway.

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Message-Id: <20070720140620.e742a2b9.akpm@linux-foundation.org>
Date:	Fri, 20 Jul 2007 14:06:20 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Konrad Rzeszutek <konrad@...nok.org>
Cc:	darnok@....org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Inhibit NMI watchdog when Alt-SysRq-T operation is
 underway.

On Fri, 20 Jul 2007 07:18:23 -0400
Konrad Rzeszutek <konrad@...nok.org> wrote:

> I tested your patch along with mine and found two things out:
> 
>  1). Missing this patch (for i386 platform)
> 
> diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
> index 90da057..9f3a7ff 100644
> --- a/arch/i386/kernel/traps.c
> +++ b/arch/i386/kernel/traps.c
> @@ -207,6 +207,7 @@ static void print_trace_address(void *da
>  {
>  	printk("%s [<%08lx>] ", (char *)data, addr);
>  	print_symbol("%s\n", addr);
> +	touch_nmi_watchdog();
>  }

ok...

>  static struct stacktrace_ops print_trace_ops = {
> 
> 
>   2). If I run Alt-SysRq-t about 5000 times in a loop, the slow down 
>       with this change is about 5%. Is this a big issue? (This was
>       testing both i686 and x86_64).
> 

I'm surprised.  I assume this was when it was printing to a high-speed
device?  console or netconsole?

I don't think we need to spend too much time optimising sysrq-T performance ;)
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