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Subject: Re: [PATCH v2 00/28] The new cgroup slab memory controller
To:     Pavel Tatashin <pasha.tatashin@soleen.com>,
        Michal Hocko <mhocko@suse.com>
Cc:     David Hildenbrand <dhildenb@redhat.com>,
        Vlastimil Babka <vbabka@suse.cz>, Roman Gushchin <guro@fb.com>,
        Bharata B Rao <bharata@linux.ibm.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Shakeel Butt <shakeelb@google.com>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Kernel Team <Kernel-team@fb.com>,
        Yafang Shao <laoar.shao@gmail.com>,
        stable <stable@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Sasha Levin <sashal@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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From:   David Hildenbrand <david@redhat.com>
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Date:   Thu, 3 Sep 2020 20:09:09 +0200
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> For performance reasons during system updates/reboots we do not erase
> memory content. The memory content is erased only on power cycle,
> which we do not do in production.
> 
> Once we hot-remove the memory, we convert it back into DAXFS PMEM
> device, format it into EXT4, mount it as DAX file system, and allow
> programs to serialize their states to it so they can read it back
> after the reboot.
> 
> During startup we mount pmem, programs read the state back, and after
> that we hotplug the PMEM DAX as a movable zone. This way during normal
> runtime we have 8G available to programs.
> 

Thanks for sharing the workflow - while it sounds somewhat sub-optimal,
I guess it gets the job done using existing tools / mechanisms.

(I remember the persistent tmpfs over kexec RFC, which tries to tackle
it by introducing something new)

-- 
Thanks,

David / dhildenb