Messages in this thread | | | Date | Mon, 1 Apr 2013 21:58:47 +0530 | Subject | Re: [PATCH v5] cpufreq: split the cpufreq_driver_lock and use the rcu (was cpufreq: cpufreq_driver_lock is hot on large systems) | From | Viresh Kumar <> |
| |
Hi Nathan,
Welcome back :)
On 1 April 2013 21:03, Nathan Zimmer <nzimmer@sgi.com> wrote:
You need to resent this patch as we don't want current mail subject as commit subject.. You could have used the area after three dashes "-" inside the commit for logs which you don't want to commit.
> The cpufreq_driver_lock is hot with some configs. > This lock covers both cpufreq_driver and cpufreq_cpu_data so part one of the
s/ so/, so/
> proposed fix is to split up the lock abit.
s/abit/a bit/
What's the other part?
> cpufreq_cpu_data is now covered by the cpufreq_data_lock. > cpufreq_driver is now covered by the cpufreq_driver lock and the rcu. > > This means that the cpufreq_driver_lock is no longer hot. > There remains some measurable heat on the cpufreq_data_lock it is significantly
s/it/but it/
> less then previous measured though. > > Cc: Viresh Kumar <viresh.kumar@linaro.org> > Cc: "Rafael J. Wysocki" <rjw@sisk.pl> > Signed-off-by: Nathan Zimmer <nzimmer@sgi.com> > --- > drivers/cpufreq/cpufreq.c | 305 +++++++++++++++++++++++++++++++++------------- > 1 file changed, 222 insertions(+), 83 deletions(-) > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> @@ -329,11 +339,23 @@ static int cpufreq_parse_governor(char *str_governor, unsigned int *policy, > struct cpufreq_governor **governor) > { > int err = -EINVAL; > - > - if (!cpufreq_driver) > + struct cpufreq_driver *driver; > + int (*setpolicy)(struct cpufreq_policy *policy); > + int (*target)(struct cpufreq_policy *policy, > + unsigned int target_freq, > + unsigned int relation);
You can keep bools here instead of complex function pointers. setpolicy_supported and target_supported
> + rcu_read_lock(); > + driver = rcu_dereference(cpufreq_driver); > + if (!driver) { > + rcu_read_unlock(); > goto out; > + } > + setpolicy = driver->setpolicy; > + target = driver->target; > + rcu_read_unlock(); > > - if (cpufreq_driver->setpolicy) { > + if (setpolicy) { > if (!strnicmp(str_governor, "performance", CPUFREQ_NAME_LEN)) { > *policy = CPUFREQ_POLICY_PERFORMANCE; > err = 0; > @@ -342,7 +364,7 @@ static int cpufreq_parse_governor(char *str_governor, unsigned int *policy, > *policy = CPUFREQ_POLICY_POWERSAVE; > err = 0; > } > - } else if (cpufreq_driver->target) { > + } else if (target) { > struct cpufreq_governor *t; > > mutex_lock(&cpufreq_governor_mutex);
> @@ -731,6 +766,8 @@ static int cpufreq_add_dev_interface(unsigned int cpu, > { > struct cpufreq_policy new_policy; > struct freq_attr **drv_attr; > + struct cpufreq_driver *driver; > + int (*exit)(struct cpufreq_policy *policy);
Declare it in the block which used it.
> if (ret) { > pr_debug("setting policy failed\n"); > - if (cpufreq_driver->exit) > - cpufreq_driver->exit(policy); > + rcu_read_lock(); > + exit = rcu_dereference(cpufreq_driver)->exit; > + if (exit) > + exit(policy); > + rcu_read_unlock(); > + > }
> @@ -1002,32 +1059,42 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif > unsigned int cpu = dev->id, ret, cpus; > unsigned long flags; > struct cpufreq_policy *data; > + struct cpufreq_driver *driver; > struct kobject *kobj; > struct completion *cmp; > struct device *cpu_dev; > + int (*target)(struct cpufreq_policy *policy, > + unsigned int target_freq, > + unsigned int relation);
can be bool?
> + int (*exit)(struct cpufreq_policy *policy); >
One more generic comment: What about a reader-writer lock for cpufreq_data_lock??
| |