linux-kernel - RE: [PATCH 1/7] rtlwifi: Neaten RT_ASSERT, RT_TRACE, RTPRINT, RT_PRINT

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Date:	Thu, 5 Jan 2012 11:25:30 -0000
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"Joe Perches" <joe@...ches.com>,
	"Larry Finger" <Larry.Finger@...inger.net>,
	"Chaoming Li" <chaoming_li@...lsil.com.cn>
Cc:	"John W. Linville" <linville@...driver.com>,
	<linux-wireless@...r.kernel.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/7] rtlwifi: Neaten RT_ASSERT, RT_TRACE, RTPRINT, RT_PRINT_DATA macros

> +#define RT_PRINT_DATA(rtlpriv, _comp, _level, _titlestring, _hexdata,
\
> +		      _hexdatalen)			 	\
> +do {							 	\
> +	if (unlikely(((_comp) & rtlpriv->dbg.global_debugcomponents) &&
\
> +		     (_level <= rtlpriv->dbg.global_debuglevel))) {
\
> +		printk(KERN_DEBUG "%s: ", KBUILD_MODNAME); 	\
> +		pr_cont("In process \"%s\" (pid %i):",	 	\
> +			current->comm, current->pid);	 	\
> +		printk(_titlestring);			 	\
> +		print_hex_dump_bytes("", DUMP_PREFIX_NONE, 	\
> +				     _hexdata, _hexdatalen);
\
> +	}
\
> +} while (0)

>From my experiences you need to use:
  if (unlikely(a) && b)
not:
  if (unlikely(a && b))
to get the expected static branch prediction.

Also, only the initial test need be in the #define,
the printfs (etc) can be moved into a real function.
This would reduce the code size (if used more than once).

	David


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