linux-kernel - Re: [PATCH 0/4] Allow persistent memory to be used like normal RAM

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Message-ID: <x49ef9b6j7m.fsf@segfault.boston.devel.redhat.com>
Date:   Thu, 17 Jan 2019 16:57:17 -0500
From:   Jeff Moyer <jmoyer@...hat.com>
To:     Keith Busch <keith.busch@...el.com>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>, thomas.lendacky@....com,
        fengguang.wu@...el.com, dave@...1.net, linux-nvdimm@...ts.01.org,
        tiwai@...e.de, zwisler@...nel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, mhocko@...e.com,
        baiyaowei@...s.chinamobile.com, ying.huang@...el.com,
        bhelgaas@...gle.com, akpm@...ux-foundation.org, bp@...e.de
Subject: Re: [PATCH 0/4] Allow persistent memory to be used like normal RAM

Keith Busch <keith.busch@...el.com> writes:

>> Keith, you seem to be implying that there are platforms that won't
>> support memory mode.  Do you also have some insight into how customers
>> want to use this, beyond my speculation?  It's really frustrating to see
>> patch sets like this go by without any real use cases provided.
>
> Right, most NFIT reporting platforms today don't have memory mode, and
> the kernel currently only supports the persistent DAX mode with these.
> This series adds another option for those platforms.

All NFIT reporting platforms today are shipping NVDIMM-Ns, where it
makes absolutely no sense to use them as regular DRAM.  I don't think
that's a good argument to make.

> I think numactl as you mentioned is the first consideration for how
> customers may make use. Dave or Dan might have other use cases in mind.

Well, it sure looks like this took a lot of work, so I thought there
were known use cases or users asking for this functionality.

Cheers,
Jeff