lkml.org 
[lkml]   [2006]   [Dec]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] WorkStruct: Implement generic UP cmpxchg() where an arch doesn't support it
On Wed, Dec 06, 2006 at 10:56:14AM -0800, Christoph Lameter wrote:
> I'd really appreciate a cmpxchg that is generically available for
> all arches. It will allow lockless implementation for various performance
> criticial portions of the kernel.

Let's recap on cmpxchg.

For CPUs with no atomic operation other than SWP, it is not lockless.
For CPUs with load locked + store conditional, it is expensive.

I've shown in the past that a generic implementation based around ll/sc
can be cheaply implemented using cmpxchg. The reverse is *not* true.

If you want an operation for performance critical portions of the
kernel, please allow architecture maintainers the freedom to use their
best performance enhancements.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of:
-
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: 2006-12-06 20:03    [W:0.102 / U:59.900 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site