linux-kernel - Re: [PATCH] DAX: warn when kmem regions are truncated for memory block alignment.

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Message-ID: <Z-v7mMZcP1JPIuj4@gourry-fedora-PF4VCD3F>
Date: Tue, 1 Apr 2025 10:43:36 -0400
From: Gregory Price <gourry@...rry.net>
To: David Hildenbrand <david@...hat.com>
Cc: dan.j.williams@...el.com, nvdimm@...ts.linux.dev,
	linux-kernel@...r.kernel.org, kernel-team@...a.com,
	vishal.l.verma@...el.com, dave.jiang@...el.com,
	linux-cxl@...r.kernel.org
Subject: Re: [PATCH] DAX: warn when kmem regions are truncated for memory
 block alignment.

On Tue, Apr 01, 2025 at 11:33:59AM +0200, David Hildenbrand wrote:
> On 31.03.25 20:27, Gregory Price wrote:
> > We discussed [1] how this auto-sizing can cause 1GB huge page
> > allocation failures (assuming you online as ZONE_NORMAL). That means
> > ACPI-informed sizing by default would potentially be harmful to existing
> > systems and adding yet-another-boot-option just seems nasty.
> > 
> > I've since dropped acpi-informed block size patch[2].  If there are opinions
> > otherwise, I can continue pushing it.
> 
> Oh, I thought we would be going forward with that. What's the reason we
> would not want to do that?
> 

It seemed like having it reduce block size by default would make 1GB huge
pages less reliable to allocate. If you think this isn't a large concern,
I can update and push again.  I suppose I could make it a build option.

Any opinions here are welcome.

~Gregory