linux-kernel - Re: [PATCH 1/6] genirq: platform wide interrupt moderation: Documentation, Kconfig, irq

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Message-ID: <CAMOZA0K3hMSE32SnyVBW5NY4V=zuC3S7ueHfZN2sAWZNqRCwvQ@mail.gmail.com>
Date: Thu, 13 Nov 2025 14:33:51 +0100
From: Luigi Rizzo <lrizzo@...gle.com>
To: Marc Zyngier <maz@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, Luigi Rizzo <rizzo.unipi@...il.com>, 
	Paolo Abeni <pabeni@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Sean Christopherson <seanjc@...gle.com>, Jacob Pan <jacob.jun.pan@...ux.intel.com>, 
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, 
	Bjorn Helgaas <bhelgaas@...gle.com>, Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH 1/6] genirq: platform wide interrupt moderation:
 Documentation, Kconfig, irq_desc

On Thu, Nov 13, 2025 at 2:25 PM Marc Zyngier <maz@...nel.org> wrote:
>
> On Wed, 12 Nov 2025 19:24:03 +0000,
> Luigi Rizzo <lrizzo@...gle.com> wrote:
>
> [...]
>
> > The system does not rely on any special hardware feature except from
> > MSI-X Pending Bit Array (PBA), a mandatory component of MSI-X
>
> Is this stuff PCI specific? if so, Why? What is the actual dependency
> on PBA? It is it just that you are relying on the ability to mask
> interrupts without losing them, something that is pretty much a given
> on any architecture?

You are right, I was overly restrictive. I only need what you say,
will replace the text accordingly.

>
> [...]
> > +To understand the motivation for this feature, we start with some
> > +background on interrupt moderation.
>
> This reads like marketing blurb. This is an API documentation, and it
> shouldn't be a description of your motivations for building it the way
> you did. I'd suggest you stick to the API, and keep the motivations
> for the cover letter.

ok will remove it.
Sorry if it reads like marketing, that is very very far from my intentions.
I just wanted to give background information in a way that is easy
to access from the source tree.

>
> > +
> > +* **Interrupt** is a mechanism to **notify** the CPU of **events**
> > +  that should be handled by software, for example, **completions**
> > +  of I/O requests (network tx/rx, disk read/writes...).
>
> That's only half of the truth, as this description only applies to
> *edge* interrupts. Level interrupts report a change in *state*, not an
> event.
>
> How do you plan to deal with interrupt moderation for level
> interrupts?

I don't. This is restricted to edge interrupts.

cheers
luigi