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

From: Peter Xu <peterx@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Christoph Lameter <cl@linux.com>,
	Aaron Tomlin <atomlin@atomlin.com>,
	Frederic Weisbecker <frederic@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH v2 10/11] mm/vmstat: switch vmstat shepherd to flush per-CPU counters remotely
Date: Thu, 2 Mar 2023 16:01:07 -0500	[thread overview]
Message-ID: <ZAEOk7GdJ0c8NS+y@x1n> (raw)
In-Reply-To: <20230209153204.901518530@redhat.com>

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