[rfc] enumerating device / bus domain information

[Warner Losh]

On Oct 7, 2014, at 7:37 PM, Adrian Chadd <adrian at FreeBSD.org> wrote:

> Hi,
> 
> Right now we're not enumerating any NUMA domain information about devices.
> 
> The more recent intel NUMA stuff has some extra affinity information
> for devices that (eventually) will allow us to bind kernel/user
> threads and/or memory allocation to devices to keep access local.
> There's a penalty for DMAing in/out of remote memory, so we'll want to
> figure out what counts as "Local" for memory allocation and perhaps
> constrain the CPU set that worker threads for a device run on.
> 
> This patch adds a few things:
> 
> * it adds a bus_if.m method for fetching the VM domain ID of a given
> device; or ENOENT if it's not in a VM domain;

Maybe a default VM domain. All devices are in VM domains :) By default
today, we have only one VM domain, and that’s the model that most of the
code expects…

Warner

> * it adds some hooks to print the numa-domain out of a device if it exists;
> * it adds hooks in srat.c to store the original proximity-id values
> and uses them to map PXM to FreeBSD VM domain IDs;
> * the ACPI code now has bus methods to enumerate which PXM (and thus
> which VM domain) a device is on.
> 
> The review for it is here:
> 
> https://reviews.freebsd.org/D906
> 
> Please ignore the vm_phys.c patch; it's purely for experimenting on my
> side and won't be committed part of this work.
> 
> Thanks,
> 
> 
> -a
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