linux-kernel - Re: [PATCH v1 5/6] mm: make vmstat

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Date:	Mon, 07 May 2012 15:33:59 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Christoph Lameter <cl@...ux.com>
CC:	Gilad Ben-Yossef <gilad@...yossef.com>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Tejun Heo <tj@...nel.org>, John Stultz <johnstul@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>, Mike Frysinger <vapier@...too.org>,
	David Rientjes <rientjes@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	Minchan Kim <minchan.kim@...il.com>,
	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	Chris Metcalf <cmetcalf@...era.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Max Krasnyansky <maxk@...lcomm.com>,
	Frederic Weisbecker <fweisbec@...il.com>, linux-mm@...ck.org,
	kosaki.motohiro@...il.com
Subject: Re: [PATCH v1 5/6] mm: make vmstat_update periodic run conditional

>> @@ -1204,8 +1265,14 @@ static int __init setup_vmstat(void)
>>
>>   	register_cpu_notifier(&vmstat_notifier);
>>
>> +	INIT_DELAYED_WORK_DEFERRABLE(&vmstat_monitor_work,
>> +				vmstat_update_monitor);
>> +	queue_delayed_work(system_unbound_wq,
>> +				&vmstat_monitor_work,
>> +				round_jiffies_relative(HZ));
>> +
>>   	for_each_online_cpu(cpu)
>> -		start_cpu_timer(cpu);
>> +		setup_cpu_timer(cpu);
>>   #endif
>>   #ifdef CONFIG_PROC_FS
>>   	proc_create("buddyinfo", S_IRUGO, NULL,&fragmentation_file_operations);
>
> So the monitoring thread just bounces around the system? Hope that the
> scheduler does the right thing to keep it on processors that do some other
> work.

Good point. Usually, all cpus have update items and monitor worker only makes
new noise. I think this feature is only useful some hpc case.  So I wonder if
this vmstat improvemnt can integrate Frederic's Nohz cpusets activity. I.e.
vmstat-update integrate timer house keeping and automatically stop when stopping
hz house keeping.

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