linux-kernel - Re: [RFC PATCH v2 0/4] mm, memory_hotplug: allocate memmap from hotadded memory

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Date:   Tue, 29 Jan 2019 09:43:59 +0100
From:   Oscar Salvador <osalvador@...e.de>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-mm@...ck.org, mhocko@...e.com, dan.j.williams@...el.com,
        Pavel.Tatashin@...rosoft.com, linux-kernel@...r.kernel.org,
        dave.hansen@...el.com
Subject: Re: [RFC PATCH v2 0/4] mm, memory_hotplug: allocate memmap from
 hotadded memory

On Fri, Jan 25, 2019 at 09:53:35AM +0100, David Hildenbrand wrote:
Hi David,

> I only had a quick glimpse. I would prefer if the caller of add_memory()
> can specify whether it would be ok to allocate vmmap from the range.
> This e.g. allows ACPI dimm code to allocate from the range, however
> other machanisms (XEN, hyper-v, virtio-mem) can allow it once they
> actually support it.

Well, I think this can be done, and it might make more sense, as we
would get rid of some other flags to prevent allocating vmemmap
besides mhp_restrictions.

> 
> Also, while s390x standby memory cannot support allocating from the
> range, virtio-mem could easily support it on s390x.
> 
> Not sure how such an interface could look like, but I would really like
> to have control over that on the add_memory() interface, not per arch.

Let me try it out and will report back.

Btw, since you are a virt-guy, would it be do feasible for you to test the patchset
on hyper-v, xen or your virtio-mem driver?

Thanks David!

-- 
Oscar Salvador
SUSE L3