Re: [v2 RFC PATCH 0/9] Another Approach to Use PMEM as NUMA Node

Yang Shi
2019-04-16T23:17:52Z

On 4/16/19 4:04 PM, Dave Hansen wrote:
> On 4/16/19 2:59 PM, Yang Shi wrote:
>> On 4/16/19 2:22 PM, Dave Hansen wrote:
>>> Keith Busch had a set of patches to let you specify the demotion order
>>> via sysfs for fun.  The rules we came up with were:
>>> 1. Pages keep no history of where they have been
>>> 2. Each node can only demote to one other node
>> Does this mean any remote node? Or just DRAM to PMEM, but remote PMEM
>> might be ok?
> In Keith's code, I don't think we differentiated. We let any node
> demote to any other node you want, as long as it follows the cycle rule.

I recall Keith's code let the userspace define the target node. Anyway,
we may need add one rule: not migrate-on-reclaim from PMEM node.
Demoting from PMEM to DRAM sounds pointless.