| Message ID | 1463576020-18597-2-git-send-email-shilpa.bhat@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
On Wed, May 18, 2016 at 2:53 PM, Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> wrote: > Add fast_switch driver callback to support frequency update in > interrupt context while using schedutil governor. Changing frequency > in interrupt context will remove the jitter on the workloads which can > be seen when a kworker thread is used for the changing the frequency. > > Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> This looks simple enough. :-) A couple of comments, though. > --- > drivers/cpufreq/powernv-cpufreq.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c > index 54c4536..4553eb6 100644 > --- a/drivers/cpufreq/powernv-cpufreq.c > +++ b/drivers/cpufreq/powernv-cpufreq.c > @@ -678,6 +678,8 @@ static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy) > for (i = 0; i < threads_per_core; i++) > cpumask_set_cpu(base + i, policy->cpus); > > + policy->fast_switch_possible = true; > + > kn = kernfs_find_and_get(policy->kobj.sd, throttle_attr_grp.name); > if (!kn) { > int ret; > @@ -854,6 +856,24 @@ static void powernv_cpufreq_stop_cpu(struct cpufreq_policy *policy) > del_timer_sync(&gpstates->timer); > } > > +static unsigned int powernv_fast_switch(struct cpufreq_policy *policy, > + unsigned int target_freq) > +{ > + int index; > + struct powernv_smp_call_data freq_data; > + > + cpufreq_frequency_table_target(policy, policy->freq_table, > + target_freq, > + CPUFREQ_RELATION_C, &index); According to the discussion I had with Peter some time ago, this should be RELATION_L or you may end up using a frequency that's not sufficient to meet a deadline somewhere. Also cpufreq_frequency_table_target() is somewhat heavy-weight especially if the table is known to be sorted (which I guess is the case). > + if (index < 0 || index >= powernv_pstate_info.nr_pstates) > + return CPUFREQ_ENTRY_INVALID; > + freq_data.pstate_id = powernv_freqs[index].driver_data; > + freq_data.gpstate_id = powernv_freqs[index].driver_data; > + set_pstate(&freq_data); > + > + return pstate_id_to_freq(-index); > +} > + > static struct cpufreq_driver powernv_cpufreq_driver = { > .name = "powernv-cpufreq", > .flags = CPUFREQ_CONST_LOOPS, > @@ -861,6 +881,7 @@ static struct cpufreq_driver powernv_cpufreq_driver = { > .exit = powernv_cpufreq_cpu_exit, > .verify = cpufreq_generic_frequency_table_verify, > .target_index = powernv_cpufreq_target_index, > + .fast_switch = powernv_fast_switch, > .get = powernv_cpufreq_get, > .stop_cpu = powernv_cpufreq_stop_cpu, > .attr = powernv_cpu_freq_attr, > -- -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c index 54c4536..4553eb6 100644 --- a/drivers/cpufreq/powernv-cpufreq.c +++ b/drivers/cpufreq/powernv-cpufreq.c @@ -678,6 +678,8 @@ static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy) for (i = 0; i < threads_per_core; i++) cpumask_set_cpu(base + i, policy->cpus); + policy->fast_switch_possible = true; + kn = kernfs_find_and_get(policy->kobj.sd, throttle_attr_grp.name); if (!kn) { int ret; @@ -854,6 +856,24 @@ static void powernv_cpufreq_stop_cpu(struct cpufreq_policy *policy) del_timer_sync(&gpstates->timer); } +static unsigned int powernv_fast_switch(struct cpufreq_policy *policy, + unsigned int target_freq) +{ + int index; + struct powernv_smp_call_data freq_data; + + cpufreq_frequency_table_target(policy, policy->freq_table, + target_freq, + CPUFREQ_RELATION_C, &index); + if (index < 0 || index >= powernv_pstate_info.nr_pstates) + return CPUFREQ_ENTRY_INVALID; + freq_data.pstate_id = powernv_freqs[index].driver_data; + freq_data.gpstate_id = powernv_freqs[index].driver_data; + set_pstate(&freq_data); + + return pstate_id_to_freq(-index); +} + static struct cpufreq_driver powernv_cpufreq_driver = { .name = "powernv-cpufreq", .flags = CPUFREQ_CONST_LOOPS, @@ -861,6 +881,7 @@ static struct cpufreq_driver powernv_cpufreq_driver = { .exit = powernv_cpufreq_cpu_exit, .verify = cpufreq_generic_frequency_table_verify, .target_index = powernv_cpufreq_target_index, + .fast_switch = powernv_fast_switch, .get = powernv_cpufreq_get, .stop_cpu = powernv_cpufreq_stop_cpu, .attr = powernv_cpu_freq_attr,
Add fast_switch driver callback to support frequency update in interrupt context while using schedutil governor. Changing frequency in interrupt context will remove the jitter on the workloads which can be seen when a kworker thread is used for the changing the frequency. Signed-off-by: Shilpasri G Bhat <shilpa.bhat@linux.vnet.ibm.com> --- drivers/cpufreq/powernv-cpufreq.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)