linux-kernel - Re: [patch v12 07/13] task isolation: sync vmstats conditional on changes

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Date:   Wed, 27 Apr 2022 10:03:58 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Marcelo Tosatti <mtosatti@...hat.com>, linux-kernel@...r.kernel.org
Cc:     Nitesh Lal <nilal@...hat.com>,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Alex Belits <abelits@...its.com>, Peter Xu <peterx@...hat.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Oscar Shiang <oscar0225@...email.tw>,
        Marcelo Tosatti <mtosatti@...hat.com>
Subject: Re: [patch v12 07/13] task isolation: sync vmstats conditional on
 changes

On Tue, Mar 15 2022 at 12:31, Marcelo Tosatti wrote:
>  
> +#ifdef CONFIG_TASK_ISOLATION
> +struct static_key vmstat_sync_enabled;

jump_label.h:

"The use of 'struct static_key' directly, is now DEPRECATED."

> +DEFINE_PER_CPU_ALIGNED(bool, vmstat_dirty);
> +
> +static inline void mark_vmstat_dirty(void)
> +{
> +	if (!static_key_false(&vmstat_sync_enabled))
> +		return;
> +
> +	raw_cpu_write(vmstat_dirty, true);

What's the justification for raw_cpu_write()?

>  
> @@ -1512,6 +1543,7 @@ static void pagetypeinfo_showfree_print(
>  		}
>  		seq_putc(m, '\n');
>  	}
> +	mark_vmstat_dirty();

Why does a function which just dumps information via /proc/pagetypeinfo
make vmstats dirty?

Thanks,

        tglx