linux-kernel - RE: [PATCH v4 2/2] ACPI: NUMA: Apply SRAT proximity domain to entire CFMWS window

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Message-ID: <6500d470d363f_19f612942b@dwillia2-xfh.jf.intel.com.notmuch>
Date:   Tue, 12 Sep 2023 14:13:20 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     <alison.schofield@...el.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "Len Brown" <lenb@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "Borislav Petkov" <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Jonathan Cameron" <Jonathan.Cameron@...wei.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Mike Rapoport <rppt@...nel.org>
CC:     Alison Schofield <alison.schofield@...el.com>, <x86@...nel.org>,
        <linux-cxl@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Derick Marks <derick.w.marks@...el.com>
Subject: RE: [PATCH v4 2/2] ACPI: NUMA: Apply SRAT proximity domain to entire
 CFMWS window

alison.schofield@ wrote:
> From: Alison Schofield <alison.schofield@...el.com>
> 
> Commit fd49f99c1809 ("ACPI: NUMA: Add a node and memblk for each
> CFMWS not in SRAT") did not account for the case where the BIOS
> only partially describes a CFMWS Window in the SRAT. That means
> the omitted address ranges, of a partially described CFMWS Window,
> do not get assigned to a NUMA node.
> 
> Replace the call to phys_to_target_node() with numa_add_memblks().
> Numa_add_memblks() searches an HPA range for existing memblk(s)
> and extends those memblk(s) to fill the entire CFMWS Window.
> 
> Extending the existing memblks is a simple strategy that reuses
> SRAT defined proximity domains from part of a window to fill out
> the entire window, based on the knowledge* that all of a CFMWS
> window is of a similar performance class.
> 
> *Note that this heuristic will evolve when CFMWS Windows present
> a wider range of characteristics. The extension of the proximity
> domain, implemented here, is likely a step in developing a more
> sophisticated performance profile in the future.
> 
> There is no change in behavior when the SRAT does not describe
> the CFMWS Window at all. In that case, a new NUMA node with a
> single memblk covering the entire CFMWS Window is created.
> 
> Fixes: fd49f99c1809 ("ACPI: NUMA: Add a node and memblk for each CFMWS not in SRAT")
> Reported-by: Derick Marks <derick.w.marks@...el.com>
> Suggested-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Alison Schofield <alison.schofield@...el.com>
> Tested-by: Derick Marks <derick.w.marks@...el.com>

Reviewed-by: Dan Williams <dan.j.williams@...el.com>