linux-kernel - Re: [PATCH 1/4] genirq/irq_sim: dispose of remaining mappings before removing the domain

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Date:   Tue, 15 Aug 2023 19:53:09 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Yury Norov <yury.norov@...il.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 1/4] genirq/irq_sim: dispose of remaining mappings before
 removing the domain

On Tue, Aug 15, 2023 at 09:09:10AM -0700, Yury Norov wrote:
> On Tue, Aug 15, 2023 at 01:38:49PM +0300, Andy Shevchenko wrote:
> > On Sat, Aug 12, 2023 at 09:44:54PM +0200, Bartosz Golaszewski wrote:

...

> > > @@ -16,12 +17,14 @@ struct irq_sim_work_ctx {
> > >  	unsigned int		irq_count;
> > >  	unsigned long		*pending;
> > >  	struct irq_domain	*domain;
> > > +	struct list_head	irqs;
> > >  };
> > >  
> > >  struct irq_sim_irq_ctx {
> > >  	int			irqnum;
> > >  	bool			enabled;
> > >  	struct irq_sim_work_ctx	*work_ctx;
> > 
> > > +	struct list_head	siblings;
> > 
> > You can reduce the code size by moving this to be the first member.
> > Not sure about struct irq_sim_work_ctx, you can play with bloat-o-meter.
> 
> Pahole you meant?

No. I meant bloat-o-meter.

...

> But as Bartosz said in the other email, "it's just good practice
> resulting from years of" kernel coding to have:
>  - members declared strongly according to the logic of the code, and
>    if no strong preference: 

>  - list head be the first element of the structure, to let compiler
>    avoid generating offsets when traversing lists;

Exactly.

>  - put elements of greater size at the beginning, so no holes will be
>    emitted like in the example above.
> 
> So I'd suggest:
> 
>   struct irq_sim_irq_ctx {
>      struct list_head        siblings;
>      struct irq_sim_work_ctx *work_ctx;
>      int                     irqnum;
>      bool                    enabled;
>   }

Yes, I like this.

-- 
With Best Regards,
Andy Shevchenko