| Message ID | 1452594267-12844-2-git-send-email-shilpa.bhat@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
On 01/12/2016 03:54 PM, Shilpasri G Bhat wrote: > 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 cpu_to_chip_id() use PIR of the cpu to find the chip id. > > Reported-by: Anton Blanchard <anton@samba.org> > Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> > --- > drivers/cpufreq/powernv-cpufreq.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c > index cb50138..597a084 100644 > --- a/drivers/cpufreq/powernv-cpufreq.c > +++ b/drivers/cpufreq/powernv-cpufreq.c > @@ -39,6 +39,7 @@ > #define PMSR_PSAFE_ENABLE (1UL << 30) > #define PMSR_SPR_EM_DISABLE (1UL << 31) > #define PMSR_MAX(x) ((x >> 32) & 0xFF) > +#define pir_to_chip_id(pir) (((pir) >> 7) & 0x3f) Since this is platform specific and true only for power8, this is not the right place to put it. Either you can move this to arch/powerpc or you can maintain a cpu to chip map within the driver. > > static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1]; > static bool rebooting, throttled, occ_reset; > @@ -312,13 +313,14 @@ 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 = pir_to_chip_id(hard_smp_processor_id()); > 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 */ > @@ -558,7 +560,8 @@ static int init_chip_info(void) > unsigned int prev_chip_id = UINT_MAX; > > for_each_possible_cpu(cpu) { > - unsigned int id = cpu_to_chip_id(cpu); > + unsigned int id = > + pir_to_chip_id(get_hard_smp_processor_id(cpu)); > > if (prev_chip_id != id) { > prev_chip_id = id; > Thanks, Shreyas
diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c index cb50138..597a084 100644 --- a/drivers/cpufreq/powernv-cpufreq.c +++ b/drivers/cpufreq/powernv-cpufreq.c @@ -39,6 +39,7 @@ #define PMSR_PSAFE_ENABLE (1UL << 30) #define PMSR_SPR_EM_DISABLE (1UL << 31) #define PMSR_MAX(x) ((x >> 32) & 0xFF) +#define pir_to_chip_id(pir) (((pir) >> 7) & 0x3f) static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1]; static bool rebooting, throttled, occ_reset; @@ -312,13 +313,14 @@ 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 = pir_to_chip_id(hard_smp_processor_id()); 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 */ @@ -558,7 +560,8 @@ static int init_chip_info(void) unsigned int prev_chip_id = UINT_MAX; for_each_possible_cpu(cpu) { - unsigned int id = cpu_to_chip_id(cpu); + unsigned int id = + pir_to_chip_id(get_hard_smp_processor_id(cpu)); if (prev_chip_id != id) { prev_chip_id = id;
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 cpu_to_chip_id() use PIR of the cpu to find the chip id. Reported-by: Anton Blanchard <anton@samba.org> Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> --- drivers/cpufreq/powernv-cpufreq.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)