linux-kernel - Re: [PATCH] genirq: Provide new interfaces for affinity hints

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Message-ID: <CAFki+LmW1d1f-mdFq8ovGERDRMkM7o=urmmQZi9cwXoR+Ydm=w@mail.gmail.com>
Date:   Fri, 4 Jun 2021 16:35:45 -0400
From:   Nitesh Lal <nilal@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Robin Murphy <robin.murphy@....com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        intel-wired-lan@...ts.osuosl.org, jbrandeb@...nel.org,
        "frederic@...nel.org" <frederic@...nel.org>,
        "juri.lelli@...hat.com" <juri.lelli@...hat.com>,
        Alex Belits <abelits@...vell.com>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "sfr@...b.auug.org.au" <sfr@...b.auug.org.au>,
        "stephen@...workplumber.org" <stephen@...workplumber.org>,
        "rppt@...ux.vnet.ibm.com" <rppt@...ux.vnet.ibm.com>,
        "jinyuqi@...wei.com" <jinyuqi@...wei.com>,
        "zhangshaokun@...ilicon.com" <zhangshaokun@...ilicon.com>,
        netdev@...r.kernel.org, chris.friesen@...driver.com,
        Marc Zyngier <maz@...nel.org>,
        Neil Horman <nhorman@...driver.com>, pjwaskiewicz@...il.com
Subject: Re: [PATCH] genirq: Provide new interfaces for affinity hints

On Fri, May 21, 2021 at 5:48 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> On Fri, May 21 2021 at 12:13, Nitesh Lal wrote:
> > On Fri, May 21, 2021 at 8:03 AM Thomas Gleixner <tglx@...utronix.de> wrote:
> >> Provide new interfaces:
> >>
> >>   irq_update_affinity_hint() - Only sets the affinity hint pointer
> >>   irq_apply_affinity_hint()  - Set the pointer and apply the affinity to
> >>                                the interrupt
> >>
> >
> > Any reason why you ruled out the usage of irq_set_affinity_and_hint()?
> > IMHO the latter makes it very clear what the function is meant to do.
>
> You're right. I was trying to phase the existing hint setter out, but
> that's probably pointless overengineering for no real value. Let me redo
> that.
>

Thomas, are you planning to send a v2 for this soon or did I somehow miss
it?

Since your other patch "genirq: Export affinity setter for modules" is
already in linux-next, I have started looking into the drivers where
we can use that.

On thinking about this whole chunk a little more, I do wonder about the
reason why we are still sticking with the hints.

The two reasons that I could come up with are:
- We are not entirely sure if irqbalance still consumes this or not
- For future use by some other userspace daemon  (?)

Does that sound right?

-- 
Thanks
Nitesh