linux-kernel - Re: [PATCH v8 1/3] memory: implement memory_block_advise/probe_max

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Message-ID: <Z-w1irf6ry2J_2PL@localhost.localdomain>
Date: Tue, 1 Apr 2025 20:50:50 +0200
From: Oscar Salvador <osalvador@...e.de>
To: Gregory Price <gourry@...rry.net>
Cc: linux-mm@...ck.org, linux-acpi@...r.kernel.org, kernel-team@...a.com,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	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, david@...hat.com,
	gregkh@...uxfoundation.org, akpm@...ux-foundation.org,
	dan.j.williams@...el.com, Jonathan.Cameron@...wei.com,
	alison.schofield@...el.com, rrichter@....com, rppt@...nel.org,
	bfaccini@...dia.com, haibo1.xu@...el.com, dave.jiang@...el.com,
	Ira Weiny <ira.weiny@...el.com>, Fan Ni <fan.ni@...sung.com>
Subject: Re: [PATCH v8 1/3] memory: implement
 memory_block_advise/probe_max_size

On Mon, Jan 27, 2025 at 10:34:03AM -0500, Gregory Price wrote:
> Hotplug memory sources may have opinions on what the memblock size
> should be - usually for alignment purposes.  For example, CXL memory
> extents can be 256MB with a matching alignment. If this size/alignment
> is smaller than the block size, it can result in stranded capacity.
> 
> Implement memory_block_advise_max_size for use prior to allocator init,
> for software to advise the system on the max block size.
> 
> Implement memory_block_probe_max_size for use by arch init code to
> calculate the best block size. Use of advice is architecture defined.
> 
> The probe value can never change after first probe. Calls to advise
> after probe will return -EBUSY to aid debugging.
> 
> On systems without hotplug, always return -ENODEV and 0 respectively.
> 
> Suggested-by: Ira Weiny <ira.weiny@...el.com>
> Acked-by: David Hildenbrand <david@...hat.com>
> Acked-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
> Acked-by: Dan Williams <dan.j.williams@...el.com>
> Tested-by: Fan Ni <fan.ni@...sung.com>
> Reviewed-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Gregory Price <gourry@...rry.net>

Acked-by: Oscar Salvador <osalvador@...e.de>


-- 
Oscar Salvador
SUSE Labs