CMPXCHG

CMPXCHG

[Scott Huang]

Four adapters need to produce data to a 
descriptor queue which is consumed by a
user process. A lock mechanism was implemented
to sync the adapters. However, this causes 
a performance hit.  Is it possible to use
CMPXCHG on Intel's i-386 to avoid the locking?
Where can I find some doc and some sample code?

Thx

-Scott

Re: CMPXCHG

[Ingo Oeser]

On Wed, May 16, 2001 at 03:37:00PM -0700, Scott Huang wrote:
> Four adapters need to produce data to a 
> descriptor queue which is consumed by a
> user process. A lock mechanism was implemented
> to sync the adapters. However, this causes 
> a performance hit.  Is it possible to use
> CMPXCHG on Intel's i-386 to avoid the locking?

What about using atomic operations for that? This is more general
and works on ALL architectures. CMPXCHG is just and special
atomic operation on ia32.

> Where can I find some doc and some sample code?

   Documentation/DocBook/kernel-hacking.tmpl

But better do

   make htmldocs 

in the kernel top level directory and read

   Documentation/DocBook/kernel-hacking/lk-hacking-guide.html

instead.

Sample code is scattered all around in the kernel.


Regards

Ingo Oeser
-- 
To the systems programmer,
users and applications serve only to provide a test load.