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Commit 96c4726f authored by Shilpasri G Bhat's avatar Shilpasri G Bhat Committed by Rafael J. Wysocki
Browse files

cpufreq: powernv: Remove cpu_to_chip_id() from hot-path 



cpu_to_chip_id() does a DT walk through to find out the chip id by
taking a contended device tree lock. This adds an unnecessary overhead
in a hot path. So instead of calling cpu_to_chip_id() everytime cache
the chip ids for all cores in the array 'core_to_chip_map' and use it
in the hotpath.

Reported-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarShilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com>
Reviewed-by: default avatarGautham R. Shenoy <ego@linux.vnet.ibm.com>
Acked-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 6d167a44

drivers/cpufreq/powernv-cpufreq.c

+20 −3
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ 


static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1];

static bool rebooting, throttled, occ_reset;

static unsigned int *core_to_chip_map;



static struct chip {

	unsigned int id;
@@ -313,13 +314,14 @@ static inline unsigned int get_nominal_index(void) 
static void powernv_cpufreq_throttle_check(void *data)

{

	unsigned int cpu = smp_processor_id();

	unsigned int chip_id = core_to_chip_map[cpu_core_index_of_thread(cpu)];

	unsigned long pmsr;

	int pmsr_pmax, i;



	pmsr = get_pmspr(SPRN_PMSR);



	for (i = 0; i < nr_chips; i++)

		if (chips[i].id == cpu_to_chip_id(cpu))

		if (chips[i].id == chip_id)

			break;



	/* Check for Pmax Capping */
@@ -559,19 +561,29 @@ static int init_chip_info(void) 
	unsigned int chip[256];

	unsigned int cpu, i;

	unsigned int prev_chip_id = UINT_MAX;

	cpumask_t cpu_mask;

	int ret = -ENOMEM;



	for_each_possible_cpu(cpu) {

	core_to_chip_map = kcalloc(cpu_nr_cores(), sizeof(unsigned int),

				   GFP_KERNEL);

	if (!core_to_chip_map)

		goto out;



	cpumask_copy(&cpu_mask, cpu_possible_mask);

	for_each_cpu(cpu, &cpu_mask) {

		unsigned int id = cpu_to_chip_id(cpu);



		if (prev_chip_id != id) {

			prev_chip_id = id;

			chip[nr_chips++] = id;

		}

		core_to_chip_map[cpu_core_index_of_thread(cpu)] = id;

		cpumask_andnot(&cpu_mask, &cpu_mask, cpu_sibling_mask(cpu));

	}



	chips = kmalloc_array(nr_chips, sizeof(struct chip), GFP_KERNEL);

	if (!chips)

		return -ENOMEM;

		goto free_chip_map;



	for (i = 0; i < nr_chips; i++) {

		chips[i].id = chip[i];
@@ -582,6 +594,10 @@ static int init_chip_info(void) 
	}



	return 0;

free_chip_map:

	kfree(core_to_chip_map);

out:

	return ret;

}



static int __init powernv_cpufreq_init(void)
@@ -616,6 +632,7 @@ static void __exit powernv_cpufreq_exit(void) 
	opal_message_notifier_unregister(OPAL_MSG_OCC,

					 &powernv_cpufreq_opal_nb);

	kfree(chips);

	kfree(core_to_chip_map);

	cpufreq_unregister_driver(&powernv_cpufreq_driver);

}

module_exit(powernv_cpufreq_exit);