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From: Frank Seidel <fseidel@suse.de>
To: Adrian Bunk <bunk@kernel.org>
Cc: Jiri Slaby <jirislaby@gmail.com>, linux-kernel@vger.kernel.org
Subject: Re: [RFC 13/13] Char: nozomi, cleanup read and write
Date: Mon, 12 Nov 2007 10:43:41 +0100	[thread overview]
Message-ID: <200711121043.42745.fseidel@suse.de> (raw)
In-Reply-To: <20071112075452.GD9771@stusta.de>

On Montag 12 November 2007 08:54:52, you (Adrian Bunk) wrote:
> On Sat, Nov 10, 2007 at 11:04:41PM +0100, Jiri Slaby wrote:
> > 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...
> 
> AFAIK there is no well defined semantics whether likely/unlikely means 
> 10:1 or 10000:1 that is guaranteed to not change during the next
> 10 years.
> 
> Unless there's a measurable difference, it's best to write readable 
> C code and simply leave all optimizations to the compiler.

>From my (totally) beginners point of view i would have guessed a chance of
very well below one percent that this condition is true could be called
"unlikely",
but i have to admit this is most probably a much too naive way of thinking,
especially in regards of compiler optimizations.
And in this special case now there are already most calls (about 80 percent)
caught by the switch-case-shortcuts anyway.

So, i'll revert it.

Thanks a lot for your feedback,
Frank	

  reply	other threads:[~2007-11-12  9:43 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-11-09 23:43 [RFC 1/13] Char: nozomi, remove unneded stuff Jiri Slaby
2007-11-09 23:44 ` [RFC 2/13] Char: nozomi, expand some functions Jiri Slaby
2007-11-10 15:41   ` Frank Seidel
2007-11-09 23:44 ` [RFC 3/13] Char: nozomi, fix fail paths Jiri Slaby
2007-11-10 15:41   ` Frank Seidel
2007-11-09 23:45 ` [RFC 4/13] Char: nozomi, tty index cleanup Jiri Slaby
2007-11-10 15:41   ` Frank Seidel
2007-11-10 15:50     ` Jiri Slaby
2007-11-09 23:46 ` [RFC 5/13] Char: nozomi, ioctls cleanup Jiri Slaby
2007-11-10 15:41   ` Frank Seidel
2007-11-09 23:46 ` [RFC 6/13] Char: nozomi, reorder and cleanup probe, remove Jiri Slaby
2007-11-10 15:42   ` Frank Seidel
2007-11-09 23:47 ` [RFC 7/13] Char: nozomi, remove struct irq Jiri Slaby
2007-11-10 15:42   ` Frank Seidel
2007-11-12 15:11   ` Frank Seidel
2007-11-09 23:48 ` [RFC 8/13] Char: nozomi, tty cleanup Jiri Slaby
2007-11-10 15:42   ` Frank Seidel
2007-11-12 18:43   ` Frank Seidel
2007-11-09 23:48 ` [RFC 9/13] Char: nozomi, lock cleanup Jiri Slaby
2007-11-10 15:42   ` Frank Seidel
2007-11-09 23:49 ` [RFC! 10/13] Char: nozomi, fix tty_flip_buffer_push Jiri Slaby
2007-11-10 15:43   ` Frank Seidel
2007-11-09 23:50 ` [RFC 11/13] Char: nozomi, remove unused includes Jiri Slaby
2007-11-10 15:43   ` Frank Seidel
2007-11-09 23:50 ` [RFC 12/13] Char: nozomi, remove void acc char2 char3 more mp mp.c mp.yy m1 nozomi2 proto rej slock1 casts Jiri Slaby
2007-11-10 15:43   ` Frank Seidel
2007-11-09 23:51 ` [RFC 13/13] Char: nozomi, cleanup read and write Jiri Slaby
2007-11-10 15:43   ` Frank Seidel
2007-11-10 16:15   ` Adrian Bunk
2007-11-10 22:04     ` Jiri Slaby
2007-11-11  2:37       ` Frank Seidel
2007-11-11 16:02         ` Frank Seidel
2007-11-12  7:54       ` Adrian Bunk
2007-11-12  9:43         ` Frank Seidel [this message]
2007-11-10 15:41 ` [RFC 1/13] Char: nozomi, remove unneded stuff Frank Seidel
2007-11-10 15:55   ` Jiri Slaby

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