lkml.org 
[lkml]   [2005]   [Aug]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [patch] IBM HDAPS accelerometer driver, with probing.
From
Date
"David S. Miller" <davem@davemloft.net> writes:

> From: Alexey Dobriyan <adobriyan@gmail.com>
> Date: Sat, 27 Aug 2005 02:58:48 +0400
>
> > What's the point of having unlikely() attached to every possible if ()?
>
> If can result in smaller code, for one thing, even if it
> isn't a performance critical path.

Really? At least on x86 it tends to generate bigger code when
block reordering is enabled because a jump forward and a jump
backward and a possible label alignment are bigger than just
a single jump forward. But then it doesn't make that much difference
because the compiler does it on its own for every block.

On x86-64 I keep it disabled because:
- it generates bigger code
- it makes the assembly code unreadable
- it doesn't seem to help that much on modern CPUs with good
branch prediction and big icaches anyways.

-Andi (who originally introduced likely/unlikely, but regrets it these
days because it's far overused and makes code uglier everywhere)
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-08-27 04:37    [W:0.046 / U:1.568 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site