linux-kernel - Re: [PATCH RFC v1 0/3] powerpc/memtrace: Don't offline memory blocks via offline

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Message-ID: <840333d6-e848-8bbc-5861-47d5a497aca7@redhat.com>
Date:   Tue, 17 Dec 2019 13:42:24 +0100
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, Allison Randal <allison@...utok.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Balbir Singh <bsingharora@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Jens Axboe <axboe@...nel.dk>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michal Hocko <mhocko@...nel.org>,
        Oscar Salvador <osalvador@...e.de>,
        Paul Mackerras <paulus@...ba.org>,
        Rashmica Gupta <rashmica.g@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH RFC v1 0/3] powerpc/memtrace: Don't offline memory blocks
 via offline_pages()

On 17.12.19 13:38, David Hildenbrand wrote:
> This RFC is based on linux-next and
> - 2 patches from "PATCH RFC v4 00/13] virtio-mem: paravirtualized memory"
>  -> "mm: Allow to offline unmovable PageOffline() pages via
>      MEM_GOING_OFFLINE" [1]
>  -> "mm/memory_hotplug: Introduce offline_and_remove_memory()" [2]
> - "mm/memory_hotplug: Don't free usage map when removing a re-added early
>    section" [3]
> 
> A branch with all patches (kept updated) is available at:
> 	https://github.com/davidhildenbrand/linux.git memtrace
> 
> Stop using offline_pages() to offline memory blocks. Allocate the memory
> blocks using alloc_contig_pages() first and offline+remove the allcoated
> memory blocks using a clean MM interface. Offlining of allocated memory is
> made possible by using PageOffline() in combination with a memory notifier
> (similar to virto-mem).
> 
> Note: In the future, we might want to switch to only removing/readding the
> page tables of the allocated memory (while still marking it PageOffline()).
> However, that might have other implications, and requires work from PPC
> people (IOW, I won't fiddle with that :) ).
> 
> [1] https://lkml.kernel.org/r/20191212171137.13872-8-david@redhat.com
> [2] https://lkml.kernel.org/r/20191212171137.13872-10-david@redhat.com
> [3] https://lkml.kernel.org/r/20191217104637.5509-1-david@redhat.com
> 
> 
> David Hildenbrand (3):
>   powerpc/memtrace: Enforce power of 2 for memory buffer size
>   powerpc/memtrace: Factor out readding memory into memtrace_free_node()
>   powerpc/memtrace: Don't offline memory blocks via offline_pages()
> 
>  arch/powerpc/platforms/powernv/Kconfig    |   1 +
>  arch/powerpc/platforms/powernv/memtrace.c | 217 ++++++++++++++--------
>  2 files changed, 136 insertions(+), 82 deletions(-)
> 

(CC linuxppc-dev on the cover letter, my fancy sendmail cc-cmd.sh script
missed it, sorry)

-- 
Thanks,

David / dhildenb