linux-kernel - Re: [PATCH v6 7/8] mm: only IPI CPUs to drain local pages if they exist

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Date:	Mon, 09 Jan 2012 17:47:30 +0100
From:	"Michal Nazarewicz" <mina86@...a86.com>
To:	"Gilad Ben-Yossef" <gilad@...yossef.com>,
	"Christoph Lameter" <cl@...ux.com>
Cc:	linux-kernel@...r.kernel.org,
	"Chris Metcalf" <cmetcalf@...era.com>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"Frederic Weisbecker" <fweisbec@...il.com>,
	"Russell King" <linux@....linux.org.uk>, linux-mm@...ck.org,
	"Pekka Enberg" <penberg@...nel.org>,
	"Matt Mackall" <mpm@...enic.com>,
	"Sasha Levin" <levinsasha928@...il.com>,
	"Rik van Riel" <riel@...hat.com>,
	"Andi Kleen" <andi@...stfloor.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Alexander Viro" <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, "Avi Kivity" <avi@...hat.com>,
	"Michal Nazarewicz" <mina86@...a86.org>
Subject: Re: [PATCH v6 7/8] mm: only IPI CPUs to drain local pages if they
 exist

On Mon, 09 Jan 2012 17:35:26 +0100, Christoph Lameter <cl@...ux.com> wrote:

> On Sun, 8 Jan 2012, Gilad Ben-Yossef wrote:
>
>> @@ -67,6 +67,14 @@ DEFINE_PER_CPU(int, numa_node);
>>  EXPORT_PER_CPU_SYMBOL(numa_node);
>>  #endif
>>
>> +/*
>> + * A global cpumask of CPUs with per-cpu pages that gets
>> + * recomputed on each drain. We use a global cpumask
>> + * here to avoid allocation on direct reclaim code path
>> + * for CONFIG_CPUMASK_OFFSTACK=y
>> + */
>> +static cpumask_var_t cpus_with_pcps;
>
> Move the static definition into drain_all_pages()?

This is initialised in setup_per_cpu_pageset() so it needs to be file scoped.

>> +
>>  #ifdef CONFIG_HAVE_MEMORYLESS_NODES
>>  /*
>>   * N.B., Do NOT reference the '_numa_mem_' per cpu variable directly.
>> @@ -1097,7 +1105,19 @@ void drain_local_pages(void *arg)
>>   */
>>  void drain_all_pages(void)
>>  {
>> -	on_each_cpu(drain_local_pages, NULL, 1);
>> +	int cpu;
>> +	struct per_cpu_pageset *pcp;
>> +	struct zone *zone;
>> +
>> +	for_each_online_cpu(cpu)
>> +		for_each_populated_zone(zone) {
>> +			pcp = per_cpu_ptr(zone->pageset, cpu);
>> +			if (pcp->pcp.count)
>> +				cpumask_set_cpu(cpu, cpus_with_pcps);
>> +			else
>> +				cpumask_clear_cpu(cpu, cpus_with_pcps);
>> +		}
>> +	on_each_cpu_mask(cpus_with_pcps, drain_local_pages, NULL, 1);
>>  }
>>
>>  #ifdef CONFIG_HIBERNATION
>> @@ -3601,6 +3621,10 @@ static void setup_zone_pageset(struct zone *zone)
>>  void __init setup_per_cpu_pageset(void)
>>  {
>>  	struct zone *zone;
>> +	int ret;
>> +
>> +	ret = zalloc_cpumask_var(&cpus_with_pcps, GFP_KERNEL);
>> +	BUG_ON(!ret);
>>
>>  	for_each_populated_zone(zone)
>>  		setup_zone_pageset(zone);
>>
>
> --
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-- 
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.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
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