Re: [RFC PATCH 0/3] Fix SLQB on memoryless configurations V2

Mel Gorman
2009-09-21T18:07:35Z

On Mon, Sep 21, 2009 at 01:54:12PM -0400, Christoph Lameter wrote:
> Lets just keep SLQB back until the basic issues with memoryless nodes are
> resolved.

It's not even super-clear that the memoryless nodes issues are entirely
related to SLQB. Sachin for example says that there was a stall issue
with memoryless nodes that could be triggered without SLQB. Sachin, is
that still accurate?

If so, it's possible that SLQB somehow exasperates the problem in some
unknown fashion.

> There does not seem to be an easy way to deal with this. Some
> thought needs to go into how memoryless node handling relates to per cpu
> lists and locking. List handling issues need to be addressed before SLQB.
> can work reliably. The same issues can surface on x86 platforms with weird
> NUMA memory setups.
>

Can you spot if there is something fundamentally wrong with patch 2? I.e. what
is wrong with treating the closest node as local instead of only the
closest node?

> Or just allow SLQB for !NUMA configurations and merge it now.
>

Forcing SLQB !NUMA will not rattle out any existing list issues
unfortunately :(.

--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab