linux-kernel - Re: [PATCH v2 00/28] The new cgroup slab memory controller

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Message-ID: <579ae7c7-6ec2-e3b1-67d4-83d0f58ec3ed@redhat.com>
Date:   Thu, 3 Sep 2020 20:09:09 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Pavel Tatashin <pasha.tatashin@...een.com>,
        Michal Hocko <mhocko@...e.com>
Cc:     David Hildenbrand <dhildenb@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>, Roman Gushchin <guro@...com>,
        Bharata B Rao <bharata@...ux.ibm.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        Yafang Shao <laoar.shao@...il.com>,
        stable <stable@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH v2 00/28] The new cgroup slab memory controller

> 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