linux-kernel - Re: [PATCH v2 10/11] mm/vmstat: switch vmstat shepherd to flush per-CPU counters remotely

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Message-ID: <ZAEOk7GdJ0c8NS+y@x1n>
Date:   Thu, 2 Mar 2023 16:01:07 -0500
From:   Peter Xu <peterx@...hat.com>
To:     Marcelo Tosatti <mtosatti@...hat.com>
Cc:     Christoph Lameter <cl@...ux.com>,
        Aaron Tomlin <atomlin@...mlin.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2 10/11] mm/vmstat: switch vmstat shepherd to flush
 per-CPU counters remotely

On Thu, Feb 09, 2023 at 12:02:00PM -0300, Marcelo Tosatti wrote:
> +#ifdef CONFIG_HAVE_CMPXCHG_LOCAL
> +/* Flush counters remotely if CPU uses cmpxchg to update its per-CPU counters */
> +static void vmstat_shepherd(struct work_struct *w)
> +{
> +	int cpu;
> +
> +	cpus_read_lock();
> +	for_each_online_cpu(cpu) {
> +		cpu_vm_stats_fold(cpu);

Nitpick: IIUC this line is the only change with CONFIG_HAVE_CMPXCHG_LOCAL
to replace the queuing.  Would it be cleaner to move the ifdef into
vmstat_shepherd, then, and keep the common logic?

> +		cond_resched();
> +	}
> +	cpus_read_unlock();
> +
> +	schedule_delayed_work(&shepherd,
> +		round_jiffies_relative(sysctl_stat_interval));
> +}
> +#else
>  static void vmstat_shepherd(struct work_struct *w)
>  {
>  	int cpu;
> @@ -2026,6 +2043,7 @@ static void vmstat_shepherd(struct work_
>  	schedule_delayed_work(&shepherd,
>  		round_jiffies_relative(sysctl_stat_interval));
>  }
> +#endif
>  
>  static void __init start_shepherd_timer(void)
>  {
> 
> 
> 

-- 
Peter Xu