linux-kernel - Re: [PATCH v3 3/3] acpi,srat: give memory block size advice based on CFMWS alignment

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Message-ID: <ZyENzGgsDOdhqBjd@kernel.org>
Date: Tue, 29 Oct 2024 18:31:08 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Gregory Price <gourry@...rry.net>
Cc: David Hildenbrand <david@...hat.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-mm@...ck.org, linux-cxl@...ck.org,
	Jonathan.Cameron@...wei.com, dan.j.williams@...el.com,
	rrichter@....com, Terry.Bowman@....com, dave.jiang@...el.com,
	ira.weiny@...el.com, alison.schofield@...el.com,
	dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org,
	tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
	rafael@...nel.org, lenb@...nel.org, osalvador@...e.de,
	gregkh@...uxfoundation.org, akpm@...ux-foundation.org
Subject: Re: [PATCH v3 3/3] acpi,srat: give memory block size advice based on
 CFMWS alignment

On Tue, Oct 29, 2024 at 09:20:44AM -0400, Gregory Price wrote:
> On Tue, Oct 29, 2024 at 01:42:12PM +0100, David Hildenbrand wrote:
> > 
> > >   static int __init acpi_parse_cfmws(union acpi_subtable_headers *header,
> > >   				   void *arg, const unsigned long table_end)
> > >   {
> > > @@ -545,6 +569,15 @@ int __init acpi_numa_init(void)
> > >   	 * Initialize a fake_pxm as the first available PXM to emulate.
> > >   	 */
> > > +	/* Align memblock size to CFMW regions if possible */
> > > +	acpi_table_parse_cedt(ACPI_CEDT_TYPE_CFMWS, acpi_align_cfmws, NULL);
> > > +
> > > +	/*
> > > +	 * Nodes start populating with blocks after this, so probe the max
> > > +	 * block size to prevent it from changing in the future.
> > > +	 */
> > > +	memory_block_probe_max_size();
> > > +
> > 
> > This looks odd. Why shouldn't we allow someone else to suggest/advise an
> > even smaller "max size" ? I'd drop that.
> > 
> 
> Ah, my reading of the numa_add_memblk path was mistaken.  I thought the
> hotplug blocks would start being created immediately after this in the
> acpi_parse_cfmws path - but memblk != memory_block x_x.

Right, we have a bunch of semi related memory blocks :)

There's mm/memblock.c for early memory description and allocation,
mm/numa_memblks.c for to describe what range belongs to which NUMA node and
there are memory blocks in drivers/base/memory.c that describe
hot-(un)plugable memory blocks.

Maybe it's time to rename memblock_* APIs back to bootmem_ :-D
 
> Will drop along with other recommended updates and submit v4.
> 
> ~Gregory

-- 
Sincerely yours,
Mike.