| Message ID | 1395317460-14811-3-git-send-email-ego@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On Thu, Mar 20, 2014 at 05:40:57PM +0530, Gautham R. Shenoy wrote: > From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> > > On POWER systems, the CPU frequency is controlled at a core-level and > hence we need to serialize so that only one of the threads in the core > switches the core's frequency at a time. > > Using a global mutex lock would needlessly serialize _all_ frequency > transitions in the system (across all cores). So introduce per-core > locking to enable finer-grained synchronization and thereby enhance > the speed and responsiveness of the cpufreq driver to varying workload > demands. > > The design of per-core locking is very simple and straight-forward: we > first define a Per-CPU lock and use the ones that belongs to the first > thread sibling of the core. > > cpu_first_thread_sibling() macro is used to find the *common* lock for > all thread siblings belonging to a core. > Forgot to add the following line. Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> > Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> > Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> > --- > drivers/cpufreq/powernv-cpufreq.c | 21 ++++++++++++++++----- > 1 file changed, 16 insertions(+), 5 deletions(-) > > diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c > index ab1551f..66dae0d 100644 > --- a/drivers/cpufreq/powernv-cpufreq.c > +++ b/drivers/cpufreq/powernv-cpufreq.c > @@ -24,8 +24,15 @@ > #include <linux/of.h> > #include <asm/cputhreads.h> > > -/* FIXME: Make this per-core */ > -static DEFINE_MUTEX(freq_switch_mutex); > +/* Per-Core locking for frequency transitions */ > +static DEFINE_PER_CPU(struct mutex, freq_switch_lock); > + > +#define lock_core_freq(cpu) \ > + mutex_lock(&per_cpu(freq_switch_lock,\ > + cpu_first_thread_sibling(cpu))); > +#define unlock_core_freq(cpu) \ > + mutex_unlock(&per_cpu(freq_switch_lock,\ > + cpu_first_thread_sibling(cpu))); > > #define POWERNV_MAX_PSTATES 256 > > @@ -221,7 +228,7 @@ static int powernv_cpufreq_target(struct cpufreq_policy *policy, > freqs.new = powernv_freqs[new_index].frequency; > freqs.cpu = policy->cpu; > > - mutex_lock(&freq_switch_mutex); > + lock_core_freq(policy->cpu); > cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE); > > pr_debug("setting frequency for cpu %d to %d kHz index %d pstate %d", > @@ -233,7 +240,7 @@ static int powernv_cpufreq_target(struct cpufreq_policy *policy, > rc = powernv_set_freq(policy->cpus, new_index); > > cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE); > - mutex_unlock(&freq_switch_mutex); > + unlock_core_freq(policy->cpu); > > return rc; > } > @@ -250,7 +257,7 @@ static struct cpufreq_driver powernv_cpufreq_driver = { > > static int __init powernv_cpufreq_init(void) > { > - int rc = 0; > + int cpu, rc = 0; > > /* Discover pstates from device tree and init */ > > @@ -260,6 +267,10 @@ static int __init powernv_cpufreq_init(void) > pr_info("powernv-cpufreq disabled\n"); > return rc; > } > + /* Init per-core mutex */ > + for_each_possible_cpu(cpu) { > + mutex_init(&per_cpu(freq_switch_lock, cpu)); > + } > > rc = cpufreq_register_driver(&powernv_cpufreq_driver); > return rc; > -- > 1.8.3.1 > -- 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
On Thu, Mar 20, 2014 at 5:40 PM, Gautham R. Shenoy <ego@linux.vnet.ibm.com> wrote: > From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> > > On POWER systems, the CPU frequency is controlled at a core-level and > hence we need to serialize so that only one of the threads in the core > switches the core's frequency at a time. Probably you don't need this anymore. https://lkml.org/lkml/2014/3/21/23 -- 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
On 03/21/2014 02:12 PM, Viresh Kumar wrote: > On Thu, Mar 20, 2014 at 5:40 PM, Gautham R. Shenoy > <ego@linux.vnet.ibm.com> wrote: >> From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> >> >> On POWER systems, the CPU frequency is controlled at a core-level and >> hence we need to serialize so that only one of the threads in the core >> switches the core's frequency at a time. > > Probably you don't need this anymore. > > https://lkml.org/lkml/2014/3/21/23 > Agreed. Regards, Srivatsa S. Bhat -- 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 ab1551f..66dae0d 100644 --- a/drivers/cpufreq/powernv-cpufreq.c +++ b/drivers/cpufreq/powernv-cpufreq.c @@ -24,8 +24,15 @@ #include <linux/of.h> #include <asm/cputhreads.h> -/* FIXME: Make this per-core */ -static DEFINE_MUTEX(freq_switch_mutex); +/* Per-Core locking for frequency transitions */ +static DEFINE_PER_CPU(struct mutex, freq_switch_lock); + +#define lock_core_freq(cpu) \ + mutex_lock(&per_cpu(freq_switch_lock,\ + cpu_first_thread_sibling(cpu))); +#define unlock_core_freq(cpu) \ + mutex_unlock(&per_cpu(freq_switch_lock,\ + cpu_first_thread_sibling(cpu))); #define POWERNV_MAX_PSTATES 256 @@ -221,7 +228,7 @@ static int powernv_cpufreq_target(struct cpufreq_policy *policy, freqs.new = powernv_freqs[new_index].frequency; freqs.cpu = policy->cpu; - mutex_lock(&freq_switch_mutex); + lock_core_freq(policy->cpu); cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE); pr_debug("setting frequency for cpu %d to %d kHz index %d pstate %d", @@ -233,7 +240,7 @@ static int powernv_cpufreq_target(struct cpufreq_policy *policy, rc = powernv_set_freq(policy->cpus, new_index); cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE); - mutex_unlock(&freq_switch_mutex); + unlock_core_freq(policy->cpu); return rc; } @@ -250,7 +257,7 @@ static struct cpufreq_driver powernv_cpufreq_driver = { static int __init powernv_cpufreq_init(void) { - int rc = 0; + int cpu, rc = 0; /* Discover pstates from device tree and init */ @@ -260,6 +267,10 @@ static int __init powernv_cpufreq_init(void) pr_info("powernv-cpufreq disabled\n"); return rc; } + /* Init per-core mutex */ + for_each_possible_cpu(cpu) { + mutex_init(&per_cpu(freq_switch_lock, cpu)); + } rc = cpufreq_register_driver(&powernv_cpufreq_driver); return rc;