linux-kernel - Re: [PATCH v3 00/26] genirq: Add support for percpu

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Message-ID: <aNZtJoFrOv8dHlkV@raptor>
Date: Fri, 26 Sep 2025 11:38:30 +0100
From: Alexandru Elisei <alexandru.elisei@....com>
To: Marc Zyngier <maz@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-acpi@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Mark Rutland <mark.rutland@....com>, Will Deacon <will@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sven Peter <sven@...nel.org>, Janne Grunau <j@...nau.net>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	James Clark <james.clark@...aro.org>,
	Jonathan Cameron <jonathan.cameron@...wei.com>
Subject: Re: [PATCH v3 00/26] genirq: Add support for percpu_devid IRQ
 affinity

Hi,

Tested this on a rockpro64 - 4xA53 + 2xA72.

On kernel v6.17-rc5, using perf to profile iperf3 for 10 seconds, the top
overhead symbol was _raw_spinlock_irq_restore() and the PMU wasn't using NMIs
(checked by printing has_nmi after armpmu_request_irq()).

With this series, same test, *irq_restore() overhead dropped to about 1% on the
little core, below 1% on the big core, and the PMU was using NMIs.

Thanks,
Alex

On Mon, Sep 22, 2025 at 09:28:07AM +0100, Marc Zyngier wrote:
> This is the third version of this series, originally posted at [1],
> which aims at allowing percpu_devid interrupt requests on the basis of
> an affinity mask. See the original submission for the details of why
> this is a desirable outcome.
> 
> From v2, we have some tidying up, thanks to Jonathan's review -- see
> changelog for details.
> 
> FWIW, I've pushed a branch at [3].
> 
> * From v2 [2]:
> 
>   - Turned of_node_to_fwnode() usage to of_fwnode_handle() (Jonathan)
> 
>   - Added a patch to finally kill of_node_to_fwnode()
> 
>   - Tidied-up documentation, comments and formatting (Jonathan)
> 
>   - Collected ABs and Rbs, with thanks (Jonathan, Suzuki, Sven)
> 
> * From v1 [1]:
> 
>   - Fixed NMI handling by getting rid of the NMI-specific flow
>     handler, which was pretty useless anyway (Will)
> 
>   - As a result, killed a metric buttload worth of GICv3 code
> 
>   - Moved irq_fwspec out of irq_fwspec_info, and passed it as a
>     parameter to irq_get_fwspec_info(), renamed from irq_get_info(),
>     and applied some generous sanitisation of the structure (Thomas)
> 
>   - Dropped the rather useless fwspec validity flag (Thomas)
> 
>   - Rejigged the PMU per-CPU handling to better deal with the DT/ACPI
>     differences, and drop some now useless patches (Will)
> 
>   - Plenty of cosmetic rework (Raphael, Thomas)
> 
> [1] https://lore.kernel.org/r/20250908163127.2462948-1-maz@kernel.org
> [2] https://lore.kernel.org/r/20250915085702.519996-1-maz@kernel.org
> [3] git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/ppi-affinity