linux-kernel - Re: [PATCH v6 05/10] mm/memory_hotplug: Shrink zones when offlining memory

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Date:   Tue, 3 Dec 2019 16:27:12 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-sh@...r.kernel.org, x86@...nel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: Re: [PATCH v6 05/10] mm/memory_hotplug: Shrink zones when offlining
 memory

On 03.12.19 16:10, Oscar Salvador wrote:
> On Sun, Oct 06, 2019 at 10:56:41AM +0200, David Hildenbrand wrote:
>> Fixes: d0dc12e86b31 ("mm/memory_hotplug: optimize memory hotplug")
>> Signed-off-by: David Hildenbrand <david@...hat.com>
> 
> I did not see anything wrong with the taken approach, and makes sense to me.
> The only thing that puzzles me is we seem to not balance spanned_pages
> for ZONE_DEVICE anymore.
> memremap_pages() increments them via move_pfn_range_to_zone, but we skip
> ZONE_DEVICE in remove_pfn_range_from_zone.

Yes, documented e.g., in

commit 7ce700bf11b5e2cb84e4352bbdf2123a7a239c84
Author: David Hildenbrand <david@...hat.com>
Date:   Thu Nov 21 17:53:56 2019 -0800

    mm/memory_hotplug: don't access uninitialized memmaps in
shrink_zone_span()

Needs some more thought - but is definitely not urgent (well, now it's
at least no longer completely broken).

> 
> That is not really related to this patch, so I might be missing something,
> but it caught my eye while reviewing this.
> 
> Anyway, for this one:
> 
> Reviewed-by: Oscar Salvador <osalvador@...e.de>
> 

Thanks!

> 
> off-topic: I __think__ we really need to trim the CC list.

Yes we should :) - done.

-- 
Thanks,

David / dhildenb