linux-kernel - Re: [PATCH] genirq: reduce irqdebug bouncing cachelines

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Message-ID: <b299bb0c-2997-6f6f-8646-4a7ecb2c79c0@kaod.org>
Date:   Tue, 13 Apr 2021 14:16:36 +0200
From:   Cédric Le Goater <clg@...d.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Nicholas Piggin <npiggin@...il.com>
CC:     <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] genirq: reduce irqdebug bouncing cachelines

Thomas,

>> We could test irq_settings_no_debug() directly under handle_nested_irq() 
>> and handle_irq_event_percpu() to avoid calling note_interrupt(), just 
>> like we do for noirqdebug.
> 
> We can do that, but then we should not just make it:
> 
>    if (!irqnodebug && !irq_settings_no_debug(desc))
>    	note_interrupt(...);
> 
> Instead have only one condition:
> 
>    if (!irq_settings_no_debug(desc))
>    	note_interrupt(...);
> 
> See the uncompiled delta patch below.

I merged this second part with the first and gave IRQF_NO_DEBUG a try 
on P8 and P9 systems and all looked fine. I should send both patches 
after IRQF_NO_AUTOEN is merged in mainline.     

Thanks,

C.