Re: [patch 01/23] Fall back on interrupt disable in cmpxchg8b on 80386 and 80486

Mathieu Desnoyers
2007-08-20T21:29:36Z

* Christoph Lameter (clameter@sgi.com) wrote:
> On Mon, 20 Aug 2007, Mathieu Desnoyers wrote:
>
> > Yes, I use it as synchronization mechanism for my buffer management algorithm
> > in LTTng. Since I write in per-cpu buffers and want to be as reentrant
> > as possible wrt other contexts (dealing with NMI as worse case, but also
> > applies to MCE..), I use local_cmpxchg to reserve space in my buffers.
> > It is faster than the standard cmpxchg.
>
> Ok I have seen these numbers in the OLS papers but I could not reproduce
> them in SLUB.
>

I'm digging in the slub with cmpxchg_local patch... first detail:
slab_alloc seems to have a return path that does not reenable
preemption... I'll keep you posted when I finish the 2.6.23-rc2-mm2
port.

Mathieu