Re: [PATCH resend^2] mm: increase RECLAIM_DISTANCE to 30

From: Dave Hansen
Date: Tue Apr 12 2011 - 20:49:15 EST

On Tue, 2011-04-12 at 17:22 -0700, David Rientjes wrote:
> On Mon, 11 Apr 2011, Dave Hansen wrote:
> I know specifically of pieces of x86 hardware that set the information
> > in the BIOS to '21' *specifically* so they'll get the zone_reclaim_mode
> > behavior which that implies.
> That doesn't seem like an argument against this patch, it's an improper
> configuration unless the remote memory access has a latency of 2.1x that
> of a local access between those two nodes. If that's the case, then it's
> accurately following the ACPI spec and the VM has made its policy decision
> to enable zone_reclaim_mode as a result.

Heh, if the kernel broke on every system that didn't follow _some_ spec,
it wouldn't boot in very many places.

When you have a hammer, everything looks like a nail. When you're a
BIOS developer, you start thwacking at the kernel with munged ACPI
tables instead of boot options. Folks do this in the real world, and I
think if we can't put their names and addresses next to the code that
works around this, we might as well put the DMI strings of their
hardware. :)

-- Dave

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