linux-kernel - Re: [PATCH 0/3] ACPI: APEI: GHES: Performance improvements for error notification handlers

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Message-ID: <aTsRE_qMKXVrvA28@agluck-desk3>
Date: Thu, 11 Dec 2025 10:44:35 -0800
From: "Luck, Tony" <tony.luck@...el.com>
To: Shuai Xue <xueshuai@...ux.alibaba.com>
CC: <guohanjun@...wei.com>, <mchehab@...nel.org>, <yazen.ghannam@....com>,
	<dave.jiang@...el.com>, <Smita.KoralahalliChannabasappa@....com>,
	<leitao@...ian.org>, <pengdonglin@...omi.com>,
	<baolin.wang@...ux.alibaba.com>, <benjamin.cheatham@....com>, <bp@...en8.de>,
	<dan.j.williams@...el.com>, <james.morse@....com>, <lenb@...nel.org>,
	<linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<rafael@...nel.org>, <zhuo.song@...ux.alibaba.com>
Subject: Re: [PATCH 0/3] ACPI: APEI: GHES: Performance improvements for error
 notification handlers

On Wed, Dec 03, 2025 at 09:02:50PM +0800, Shuai Xue wrote:
> This patch series improves the performance of GHES error notification handlers
> (NMI and SEA) by optimizing how they check for active error conditions.
> 
> Currently, both ghes_notify_nmi() and ghes_notify_sea() perform expensive
> operations on each invocation to determine if there are actual error records
> to process. This includes mapping/unmapping physical addresses and accessing
> hardware registers, which causes significant overhead especially on systems
> with many cores.
> 
> The optimizations introduced in this series:
> 1. Pre-map error status registers during initialization
> 2. Directly check for active errors using mapped virtual addresses
> 3. Extract common functionality into reusable helper functions
> 4. Apply the same optimization to both NMI and SEA handlers
> 
> These changes significantly reduce the overhead of error checking:
> - NMI handler: From ~15,000 TSC cycles to ~900 cycles
> - SEA handler: From 8,138.3 ns to a much faster check
> 
> The initial idea for this optimization came from Tony Luck [1], who identified
> and implemented the approach for the NMI handler. This series extends the
> same concept to the SEA handler and refactors common code into shared helpers.
> 
> Patch 1 (Tony Luck): Improves ghes_notify_nmi() status check by pre-mapping
>                      error status registers and avoiding repeated mappings.
> 
> Patch 2 (Shuai Xue): Extracts common helper functions for error status handling
>                      to eliminate code duplication.
> 
> Patch 3 (Shuai Xue): Applies the same optimization to ghes_notify_sea() to improve
>                      ARMv8 system performance.
> 
> https://lore.kernel.org/lkml/20251103230547.8715-1-tony.luck@intel.com/

Thanks for the improvements to extend coverage to SEA.

Tested-by: Tony Luck <tony.luck@...el.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>

-Tony