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Commit 57f848a9 authored by Liam Mark's avatar Liam Mark
Browse files

mm: vmscan: support setting of kswapd cpu affinity 



Allow the kswapd cpu affinity to be configured.
There can be power benefits on certain targets when limiting kswapd
to run only on certain cores.

CRs-fixed: 752344
Change-Id: I8a83337ff313a7e0324361140398226a09f8be0f
Signed-off-by: default avatarLiam Mark <lmark@codeaurora.org>
parent fd7e6316

mm/Kconfig

+13 −0
Original line number Diff line number Diff line
@@ -540,3 +540,16 @@ config BALANCE_ANON_FILE_RECLAIM 


config GENERIC_EARLY_IOREMAP

	bool



config KSWAPD_CPU_AFFINITY_MASK

	string "kswapd cpu affinity mask"

	depends on SMP

	help

	  Set the cpu affinity for the kswapd task.

	  There can be power benefits on certain targets when limiting kswapd

	  to run only on certain cores.

	  The cpu affinity bitmask is represented by a hex string where commas

	  group hex digits into chunks.  Each chunk defines exactly 32 bits of

	  the resultant bitmask.

	  For example to limit kswapd to the first 4 cores use the following:

	  CONFIG_KSWAPD_CPU_AFFINITY_MASK="f"

mm/vmscan.c

+28 −2
Original line number Diff line number Diff line
@@ -133,6 +133,12 @@ struct scan_control { 
int vm_swappiness = 60;

unsigned long vm_total_pages;	/* The total number of pages which the VM controls */



#ifdef CONFIG_KSWAPD_CPU_AFFINITY_MASK

char *kswapd_cpu_mask = CONFIG_KSWAPD_CPU_AFFINITY_MASK;

#else

char *kswapd_cpu_mask = NULL;

#endif



static LIST_HEAD(shrinker_list);

static DECLARE_RWSEM(shrinker_rwsem);
@@ -3077,7 +3083,7 @@ static int kswapd(void *p) 


	lockdep_set_current_reclaim_state(GFP_KERNEL);



	if (!cpumask_empty(cpumask))

	if (kswapd_cpu_mask == NULL && !cpumask_empty(cpumask))

		set_cpus_allowed_ptr(tsk, cpumask);

	current->reclaim_state = &reclaim_state;
@@ -3251,6 +3257,22 @@ static int cpu_callback(struct notifier_block *nfb, unsigned long action, 
	return NOTIFY_OK;

}



static int set_kswapd_cpu_mask(pg_data_t *pgdat)

{

	int ret = 0;

	cpumask_t tmask;



	if (!kswapd_cpu_mask)

		return 0;



	cpus_clear(tmask);

	ret = cpumask_parse(kswapd_cpu_mask, &tmask);

	if (ret)

		return ret;



	return set_cpus_allowed_ptr(pgdat->kswapd, &tmask);

}



/*

 * This kswapd start function will be called by init and node-hot-add.

 * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added.
@@ -3270,6 +3292,9 @@ int kswapd_run(int nid) 
		pr_err("Failed to start kswapd on node %d\n", nid);

		ret = PTR_ERR(pgdat->kswapd);

		pgdat->kswapd = NULL;

	} else if (kswapd_cpu_mask) {

		if (set_kswapd_cpu_mask(pgdat))

			pr_warn("error setting kswapd cpu affinity mask\n");

	}

	return ret;

}
@@ -3295,6 +3320,7 @@ static int __init kswapd_init(void) 
	swap_setup();

	for_each_node_state(nid, N_MEMORY)

 		kswapd_run(nid);

	if (kswapd_cpu_mask == NULL)

		hotcpu_notifier(cpu_callback, 0);

	return 0;

}