Commit 54880b5a authored by Frederic Weisbecker's avatar Frederic Weisbecker
Browse files

mm: Create/affine kcompactd to its preferred node 



Kcompactd is dedicated to a specific node. As such it wants to be
preferrably affine to it, memory and CPUs-wise.

Use the proper kthread API to achieve that. As a bonus it takes care of
CPU-hotplug events and CPU-isolation on its behalf.

Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
parent d1a89197

mm/compaction.c

+3 −40
Original line number Diff line number Diff line
@@ -3154,15 +3154,9 @@ void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx) 
static int kcompactd(void *p)

{

	pg_data_t *pgdat = (pg_data_t *)p;

	struct task_struct *tsk = current;

	long default_timeout = msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC);

	long timeout = default_timeout;



	const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);



	if (!cpumask_empty(cpumask))

		set_cpus_allowed_ptr(tsk, cpumask);



	set_freezable();



	pgdat->kcompactd_max_order = 0;
@@ -3233,10 +3227,12 @@ void __meminit kcompactd_run(int nid) 
	if (pgdat->kcompactd)

		return;



	pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid);

	pgdat->kcompactd = kthread_create_on_node(kcompactd, pgdat, nid, "kcompactd%d", nid);

	if (IS_ERR(pgdat->kcompactd)) {

		pr_err("Failed to start kcompactd on node %d\n", nid);

		pgdat->kcompactd = NULL;

	} else {

		wake_up_process(pgdat->kcompactd);

	}

}
@@ -3254,30 +3250,6 @@ void __meminit kcompactd_stop(int nid) 
	}

}



/*

 * It's optimal to keep kcompactd on the same CPUs as their memory, but

 * not required for correctness. So if the last cpu in a node goes

 * away, we get changed to run anywhere: as the first one comes back,

 * restore their cpu bindings.

 */

static int kcompactd_cpu_online(unsigned int cpu)

{

	int nid;



	for_each_node_state(nid, N_MEMORY) {

		pg_data_t *pgdat = NODE_DATA(nid);

		const struct cpumask *mask;



		mask = cpumask_of_node(pgdat->node_id);



		if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)

			/* One of our CPUs online: restore mask */

			if (pgdat->kcompactd)

				set_cpus_allowed_ptr(pgdat->kcompactd, mask);

	}

	return 0;

}



static int proc_dointvec_minmax_warn_RT_change(const struct ctl_table *table,

		int write, void *buffer, size_t *lenp, loff_t *ppos)

{
@@ -3337,15 +3309,6 @@ static struct ctl_table vm_compaction[] = { 
static int __init kcompactd_init(void)

{

	int nid;

	int ret;



	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,

					"mm/compaction:online",

					kcompactd_cpu_online, NULL);

	if (ret < 0) {

		pr_err("kcompactd: failed to register hotplug callbacks.\n");

		return ret;

	}



	for_each_node_state(nid, N_MEMORY)

		kcompactd_run(nid);