linux-kernel - Re: [PATCH v1] mm/memory_hotplug: drop "online" parameter from add_memory

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Message-ID: <a97fcf28-ef71-2b49-c25c-bc96cff8366b@redhat.com>
Date:   Fri, 23 Nov 2018 13:58:16 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Oscar Salvador <osalvador@...e.de>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Arun KS <arunks@...eaurora.org>,
        Mathieu Malaterre <malat@...ian.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH v1] mm/memory_hotplug: drop "online" parameter from
 add_memory_resource()

On 23.11.18 13:54, Michal Hocko wrote:
> On Fri 23-11-18 13:37:40, David Hildenbrand wrote:
>> User space should always be in charge of how to online memory and
>> if memory should be onlined automatically in the kernel. Let's drop the
>> parameter to overwrite this - XEN passes memhp_auto_online, just like
>> add_memory(), so we can directly use that instead internally.
> 
> Heh, I wanted to get rid of memhp_auto_online so much and now we have it
> in the core memory_hotplug. Not a win on my side I would say :/

That is actually a good point: Can we remove memhp_auto_online or is it
already some sort of kernel ABI?

(as it is exported via /sys/devices/system/memory/auto_online_blocks)

> On the other hand this can be seen as a cleanup because it removes that
> ambiguity that some callers might be unaware of the memhp_auto_online
> leading to a different behavior.

I would say this patch is a step into the right direction - remove the
flag from the interfaces, then drop it (eventually, as stated not sure
if that train has left the station).

> 
>> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
>> Cc: Juergen Gross <jgross@...e.com>
>> Cc: Stefano Stabellini <sstabellini@...nel.org>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: Dan Williams <dan.j.williams@...el.com>
>> Cc: Oscar Salvador <osalvador@...e.de>
>> Cc: Pavel Tatashin <pasha.tatashin@...cle.com>
>> Cc: Michal Hocko <mhocko@...e.com>
>> Cc: David Hildenbrand <david@...hat.com>
>> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
>> Cc: Arun KS <arunks@...eaurora.org>
>> Cc: Mathieu Malaterre <malat@...ian.org>
>> Cc: Stephen Rothwell <sfr@...b.auug.org.au>
>> Signed-off-by: David Hildenbrand <david@...hat.com>
> 
> Acked-by: Michal Hocko <mhocko@...e.com>
> 


-- 

Thanks,

David / dhildenb