Messages in this thread Patch in this message | | | From | Shilpasri G Bhat <> | Subject | [PATCH v7 3/6] cpufreq: powernv: Remove cpu_to_chip_id() from hot-path | Date | Thu, 28 Jan 2016 12:55:38 +0530 |
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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: Anton Blanchard <anton@samba.org> Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> --- Changes from v6: - Minor changes to move the code 'cpumask_copy()' after 'core_to_chip_map' is allocated. - Move 'kfree(chips)' to a separate patch.
No changes from v5.
Changes from v4: - Taken care of Shreyas's comments to add a core_to_chip_map array to store the chip id.
drivers/cpufreq/powernv-cpufreq.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c index a271b0f..c670314 100644 --- a/drivers/cpufreq/powernv-cpufreq.c +++ b/drivers/cpufreq/powernv-cpufreq.c @@ -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); -- 1.9.3
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