Re: [PATCH v3 0/3] create sysfs representation of ACPI HMAT

[Anshuman Khandual]

On 12/22/2017 10:43 PM, Dave Hansen wrote:
> On 12/21/2017 07:09 PM, Anshuman Khandual wrote:
>> I had presented a proposal for NUMA redesign in the Plumbers Conference this
>> year where various memory devices with different kind of memory attributes
>> can be represented in the kernel and be used explicitly from the user space.
>> Here is the link to the proposal if you feel interested. The proposal is
>> very intrusive and also I dont have a RFC for it yet for discussion here.
> I think that's the best reason to "re-use NUMA" for this: it's _not_
> intrusive.
> 
> Also, from an x86 perspective, these HMAT systems *will* be out there.
> Old versions of Linux *will* see different types of memory as separate
> NUMA nodes.  So, if we are going to do something different, it's going
> to be interesting to un-teach those systems about using the NUMA APIs
> for this.  That ship has sailed.

I understand the need to fetch these details from ACPI/DT for
applications to target these distinct memory only NUMA nodes.
This can be done by parsing from platform specific values from
/proc/acpi/ or /proc/device-tree/ interfaces. This can be a
short term solution before NUMA redesign can be figured out.
But adding generic devices like "hmat" in the /sys/devices/
path which will be locked for good, seems problematic.