Re: [EXT] Re: [RFC PATCH 0/2] Node migration between memory tiers

[Michal Hocko]

On Tue 05-12-23 01:26:07, Srinivasulu Thanneeru wrote:
> 
> 
> On 12/4/2023 9:13 PM, Michal Hocko wrote:
> > CAUTION: EXTERNAL EMAIL. Do not click links or open attachments unless you recognize the sender and were expecting this message.
> > 
> > 
> > On Fri 01-12-23 03:34:20, sthanneeru.opensrc@xxxxxxxxxx wrote:
> > > From: Srinivasulu Thanneeru <sthanneeru.opensrc@xxxxxxxxxx>
> > > 
> > > The memory tiers feature allows nodes with similar memory types
> > > or performance characteristics to be grouped together in a
> > > memory tier. However, there is currently no provision for
> > > moving a node from one tier to another on demand.
> > 
> > Could you expand on why this is really needed/necessary? What is the
> > actual usecase?
> 
> Hi Michal Hock,
> 
> Following two use-cases we have observed.
> 1. It is not accurate to group similar memory types in the same tier,
>    because even similar memory types may have different speed grades.

Presumably they are grouped based on a HW configuration. Does that mean
that the configuration is wrong? Are you trying to workaround that by
this interface?

> 2. Some systems boots up with CXL devices and DRAM on the same memory-tier,
> we need a way to move the CXL nodes to the correct tier from the user space.

Again, could you expand a bit more and explain why this cannot be
configured automatically?
-- 
Michal Hocko
SUSE Labs