Re: [RFC PATCH 0/4]: affinity-on-next-touch

[Andi Kleen <andi@firstfloor.org>]

On Mon, May 11, 2009 at 04:54:40PM +0200, Stefan Lankes wrote:
> > From: Andi Kleen [mailto:andi@firstfloor.org]
> > 
> > Stefan Lankes <lankes@lfbs.rwth-aachen.de> writes:
> > >
> > > [Patch 1/4]: Extend the system call madvise with a new parameter
> > > MADV_ACCESS_LWP (the same as used in Solaris). The specified memory
> > area
> > 
> > Linux does NUMA memory policies in mbind(), not madvise()
> > Also if there's a new NUMA policy it should be in the standard
> > Linux NUMA memory policy frame work, not inventing a new one
> 
> By default, mbind only has an effect on new allocations. I think that this

Nope, it affects existing pages too, it can even move pages
if you ask for it.

> is different from what we need for applications with dynamic memory access
> patterns. The app gives the kernel a hint that the access pattern has been
> changed and the kernel has to redistribute the pages which are already
> allocated.

MF_MOVE


> For instance, Norden's PDE solvers using adaptive mesh refinements (AMR) [1]
> is an application with a dynamic access pattern. We use this example to
> evaluate the performance of our patch. We ran this solver on our
> quad-socket, dual-core Opteron 875 (2.2GHz) system running CentOS 5.2. The
> code was already optimized for NUMA architectures. Before the arrays are
> initialized, the threads are bound to one core. In our test case, the solver
> needs 5318s. If we use our kernel extension, the solver needs 4489s. 

Okay that sounds like good numbers. 

> Currently, we are testing some other apps.

Please keep the list updated.

-Andi
-- 
ak@linux.intel.com -- Speaking for myself only.