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SubjectRe: [PATCH] genirq: reduce irqdebug bouncing cachelines
On 4/13/21 10:24 PM, Thomas Gleixner wrote:
> On Tue, Apr 13 2021 at 14:16, Cédric Le Goater wrote:
>>>> 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.
> Does having that NODEBUG flag set on the IPI irqs make a measurable
> difference or is it just too small to matter?

It does not add much benefits on the 2s and 4s systems but I will give it
a try on bigger ones when I can grab them. Then we can decide if it is
worth merging.



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