Re: [PATCH 00/35] AutoNUMA alpha14

Andrea Arcangeli
2012-05-29T16:10:23Z

Hi,

On Tue, May 29, 2012 at 10:53:32AM -0500, Christoph Lameter wrote:
> then does the distribution of the load on its own. NUMA aware applications
> like that do not benefit and do not need either of the mechanisms proposed
> here.

Agreed. Who changes the apps to optimize things to that lowlevel, I
doubt wants to risk to hit on on a migrate on fault (or AutoNUMA async
migration for that matter).

> I think the proof that we need is that a general mix of applications
> actually benefits from an auto migration scheme. I would also like to see

Agreed.

> that it does no harm to existing NUMA aware applications.

As far as AutoNUMA is concerned, it will be a total bypass whenever
the mpol isn't MPOL_DEFAULT. So it shouldn't harm. Shared memory is
also bypassed.

It only alters the beahvior of MPOL_DEFAULT, any other kind of
mempolicy is unaffected, and all CPU bindings are also unaffected.

If an app has only a few vmas that are MPOL_DEFAULT those few will be
handled by AutoNUMA.

If people thinks AutoMigration is a better name I should rename
it. It's up to you. I thought using a "NUMA" suffix would make it
more intuitive that if your hardware isn't NUMA, this won't do
anything at all. Migration as a feature isn't limited to NUMA (see
compaction etc..). Comments welcome.