linux-kernel - Re: [RFC 13/13] Char: nozomi, cleanup read and write

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Date:	Sat, 10 Nov 2007 23:04:41 +0100
From:	Jiri Slaby <jirislaby@...il.com>
To:	Adrian Bunk <bunk@...nel.org>
CC:	linux-kernel@...r.kernel.org, Frank Seidel <fseidel@...e.de>
Subject: Re: [RFC 13/13] Char: nozomi, cleanup read and write

On 11/10/2007 05:15 PM, Adrian Bunk wrote:
> On Fri, Nov 09, 2007 at 06:51:35PM -0500, Jiri Slaby wrote:
>> ...
>> --- a/drivers/char/nozomi.c
>> +++ b/drivers/char/nozomi.c
>> ...
>> -		if (size_bytes - i == 2) {
>> +		if (unlikely(size_bytes - i == 2)) {
>> ...
> 
> Please don't add likely/unlikely in drivers unless it brings a 
> measurable improvement.

Why? Anyway I think this is the case. The body of the then branch is executed at
most once, while the else branch each time but last. If you write/read 1002
bytes, it means 250:1. ...and it's invoked from interrupt too...

regards,
-- 
Jiri Slaby (jirislaby@...il.com)
Faculty of Informatics, Masaryk University
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