linux-kernel - Re: [PATCH v7 2/2] mm: make lru_add_drain

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Date:	Wed, 14 Aug 2013 13:18:31 -0400
From:	Chris Metcalf <cmetcalf@...era.com>
To:	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Cody P Schafer <cody@...ux.vnet.ibm.com>
Subject: Re: [PATCH v7 2/2] mm: make lru_add_drain_all() selective

On 8/14/2013 12:57 PM, Tejun Heo wrote:
> Hello, Chris.
>
> On Wed, Aug 14, 2013 at 12:03:39PM -0400, Chris Metcalf wrote:
>> Tejun, I don't know if you have a better idea for how to mark a
>> work_struct as being "not used" so we can set and test it here.
>> Is setting entry.next to NULL good?  Should we offer it as an API
>> in the workqueue header?
> Maybe simply defining a static cpumask would be cleaner?

I think you're right, actually.  Andrew, Tejun, how does this look?


static DEFINE_PER_CPU(struct work_struct, lru_add_drain_work);

void lru_add_drain_all(void)
{
        static DEFINE_MUTEX(lock);
        static struct cpumask has_work;
        int cpu;

        mutex_lock(&lock);
        get_online_cpus();
        cpumask_clear(&has_work);

        for_each_online_cpu(cpu) {
                struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);

                if (pagevec_count(&per_cpu(lru_add_pvec, cpu)) ||
                    pagevec_count(&per_cpu(lru_rotate_pvecs, cpu)) ||
                    pagevec_count(&per_cpu(lru_deactivate_pvecs, cpu)) ||
                    need_activate_page_drain(cpu)) {
                        INIT_WORK(work, lru_add_drain_per_cpu);
                        schedule_work_on(cpu, work);
                        cpumask_set_cpu(cpu, &has_work);
                }
        }

        for_each_cpu(cpu, &has_work)
                flush_work(&per_cpu(lru_add_drain_work, cpu));

        put_online_cpus();
        mutex_unlock(&lock);
}

-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com

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