linux-kernel - Re: [GIT PULL] device-dax for 5.1: PMEM as RAM

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Message-ID: <CAPcyv4g+reM9y+CiGXpxBYMQZ-Yh4LuXDi2530FR0zt3o6J8Hg@mail.gmail.com>
Date:   Wed, 15 May 2019 13:26:16 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux MM <linux-mm@...ck.org>,
        Dave Hansen <dave.hansen@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        Vishal L Verma <vishal.l.verma@...el.com>
Subject: Re: [GIT PULL] device-dax for 5.1: PMEM as RAM

On Mon, Mar 11, 2019 at 5:08 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Mon, Mar 11, 2019 at 8:37 AM Dan Williams <dan.j.williams@...el.com> wrote:
> >
> > Another feature the userspace tooling can support for the PMEM as RAM
> > case is the ability to complete an Address Range Scrub of the range
> > before it is added to the core-mm. I.e at least ensure that previously
> > encountered poison is eliminated.
>
> Ok, so this at least makes sense as an argument to me.
>
> In the "PMEM as filesystem" part, the errors have long-term history,
> while in "PMEM as RAM" the memory may be physically the same thing,
> but it doesn't have the history and as such may not be prone to
> long-term errors the same way.
>
> So that validly argues that yes, when used as RAM, the likelihood for
> errors is much lower because they don't accumulate the same way.

In case anyone is looking for the above mentioned tooling for use with
the v5.1 kernel, Vishal has released ndctl-v65 with the new
"clear-errors" command [1].

[1]: https://pmem.io/ndctl/ndctl-clear-errors.html