[PATCH] kill massive wireless-related log spam

[PATCH] kill massive wireless-related log spam

[Jeff Garzik]

Please apply to 2.6.14-rc.

Although this message is having the intended effect of causing wireless
driver maintainers to upgrade their code, I never should have merged
this patch in its present form.  Leading to tons of bug reports and
unhappy users.

Some wireless apps poll for statistics regularly, which leads to a
printk() every single time they ask for stats.  That's a little bit
_too_ much of a reminder that the driver is using an old API.

Change this to printing out the message once, per kernel boot.

diff --git a/net/core/wireless.c b/net/core/wireless.c
index d17f158..271ddb3 100644
--- a/net/core/wireless.c
+++ b/net/core/wireless.c
@@ -455,10 +455,15 @@ static inline struct iw_statistics *get_
 
 	/* Old location, field to be removed in next WE */
 	if(dev->get_wireless_stats) {
-		printk(KERN_DEBUG "%s (WE) : Driver using old /proc/net/wireless support, please fix driver !\n",
-		       dev->name);
+		static int printed_message;
+
+		if (!printed_message++)
+			printk(KERN_DEBUG "%s (WE) : Driver using old /proc/net/wireless support, please fix driver !\n",
+				dev->name);
+
 		return dev->get_wireless_stats(dev);
 	}
+
 	/* Not found */
 	return (struct iw_statistics *) NULL;
 }

Re: [PATCH] kill massive wireless-related log spam

[Andi Kleen]

On Wednesday 26 October 2005 06:28, Jeff Garzik wrote:

> Change this to printing out the message once, per kernel boot.

It doesn't do that. It prints it once every 2^32 calls. Also
the ++ causes unnecessary dirty cache lines in normal operation.

-Andi
> 
> diff --git a/net/core/wireless.c b/net/core/wireless.c
> index d17f158..271ddb3 100644
> --- a/net/core/wireless.c
> +++ b/net/core/wireless.c
> @@ -455,10 +455,15 @@ static inline struct iw_statistics *get_
>  
>  	/* Old location, field to be removed in next WE */
>  	if(dev->get_wireless_stats) {
> -		printk(KERN_DEBUG "%s (WE) : Driver using old /proc/net/wireless support, please fix driver !\n",
> -		       dev->name);
> +		static int printed_message;
> +
> +		if (!printed_message++)
> +			printk(KERN_DEBUG "%s (WE) : Driver using old /proc/net/wireless support, please fix driver !\n",
> +				dev->name);
> +
>  		return dev->get_wireless_stats(dev);
>  	}
> +

Re: [PATCH] kill massive wireless-related log spam

[Jesper Juhl]

On 10/26/05, Andi Kleen <ak@suse.de> wrote:
> On Wednesday 26 October 2005 06:28, Jeff Garzik wrote:
>
> > Change this to printing out the message once, per kernel boot.
>
> It doesn't do that. It prints it once every 2^32 calls. Also

I noted that as well. How about just using something along the lines of

static unsigned char printed_message = 0;
if (!printed_message) {
    printk(...);
    printed_message++;
}


--
Jesper Juhl <jesper.juhl@gmail.com>
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Re: [PATCH] kill massive wireless-related log spam

[J.A. Magallon]

On 2005.10.26, at 17:23, Jesper Juhl wrote:

> On 10/26/05, Andi Kleen <ak@suse.de> wrote:
>
>> On Wednesday 26 October 2005 06:28, Jeff Garzik wrote:
>>
>>
>>> Change this to printing out the message once, per kernel boot.
>>>
>>
>> It doesn't do that. It prints it once every 2^32 calls. Also
>>
>
> I noted that as well. How about just using something along the  
> lines of
>
> static unsigned char printed_message = 0;
> if (!printed_message) {
>     printk(...);
>     printed_message++;
> }

Sorry, but why not the old good

     printed_message = 1

??
What kind of microoptimization is that ?

--
J.A. Magallon <jamagallon()able!es>   \          Software is like sex:
wolverine                              \    It's better when it's free
MacOS X 10.4.2, Darwin Kernel Version 8.2.0

Re: [PATCH] kill massive wireless-related log spam

[Jesper Juhl]

On 10/26/05, J.A. Magallon <jamagallon@able.es> wrote:
>
> On 2005.10.26, at 17:23, Jesper Juhl wrote:
>
> > On 10/26/05, Andi Kleen <ak@suse.de> wrote:
> >
> >> On Wednesday 26 October 2005 06:28, Jeff Garzik wrote:
> >>
> >>
> >>> Change this to printing out the message once, per kernel boot.
> >>>
> >>
> >> It doesn't do that. It prints it once every 2^32 calls. Also
> >>
> >
> > I noted that as well. How about just using something along the
> > lines of
> >
> > static unsigned char printed_message = 0;
> > if (!printed_message) {
> >     printk(...);
> >     printed_message++;
> > }
>
> Sorry, but why not the old good
>
>      printed_message = 1
>
> ??
> What kind of microoptimization is that ?
>
Does it really matter?   I needed to pick one of
printed_message=1; or printed_message++;
the end result is the same, so I just picked one at random.
But now that you mention it, I guess ++ would turn into "inc" which
should be faster than an assignment... but it *doesn't matter*... I
was not trying to optimize anything, just make the code work properly
- as in, only ever print the message once...


--
Jesper Juhl <jesper.juhl@gmail.com>
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Re: [PATCH] kill massive wireless-related log spam

[Jeff Garzik]

Andi Kleen wrote:
> On Wednesday 26 October 2005 06:28, Jeff Garzik wrote:
> 
> 
>>Change this to printing out the message once, per kernel boot.
> 
> 
> It doesn't do that. It prints it once every 2^32 calls. Also

...which is effectively one per kernel boot


> the ++ causes unnecessary dirty cache lines in normal operation.

Not a hot path operation by any stretch of the imagination, so that's fine.

	Jeff

Re: [PATCH] kill massive wireless-related log spam

[Horst von Brand]

Jeff Garzik <jgarzik@pobox.com> wrote:
> Andi Kleen wrote:
> > On Wednesday 26 October 2005 06:28, Jeff Garzik wrote:
> >
> >>Change this to printing out the message once, per kernel boot.
> > It doesn't do that. It prints it once every 2^32 calls. Also
> 
> ...which is effectively one per kernel boot
> 
> 
> > the ++ causes unnecessary dirty cache lines in normal operation.

> Not a hot path operation by any stretch of the imagination, so that's
fine.

Right. As the "++" is inside "if(!printed) { ... }" it clearly isn't ;-)
-- 
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