| Message ID | 1538654644-32705-1-git-send-email-daniel.lezcano@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | [V2,1/2] sched: Factor out nr_iowait and nr_iowait_cpu | expand |
On Thu, Oct 04, 2018 at 02:04:03PM +0200, Daniel Lezcano wrote: > The function get_loadavg() returns almost always zero. To be more > precise, statistically speaking for a total of 1023379 times passing > in the function, the load is equal to zero 1020728 times, greater than > 100, 610 times, the remaining is between 0 and 5. > > In 2011, the get_loadavg() was removed from the Android tree because > of the above [1]. At this time, the load was: > > unsigned long this_cpu_load(void) > { > struct rq *this = this_rq(); > return this->cpu_load[0]; > } > > In 2014, the code was changed by commit 372ba8cb46b2 (cpuidle: menu: Lookup CPU > runqueues less) and the load is: > > void get_iowait_load(unsigned long *nr_waiters, unsigned long *load) > { > struct rq *rq = this_rq(); > *nr_waiters = atomic_read(&rq->nr_iowait); > *load = rq->load.weight; > } > > with the same result. > > Both measurements show using the load in this code path does no matter > anymore. Removing it. > > [1] https://android.googlesource.com/kernel/common/+/4dedd9f124703207895777ac6e91dacde0f7cc17 > > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Todd Kjos <tkjos@google.com> > Cc: Joel Fernandes <joelaf@google.com> > Cc: Colin Cross <ccross@android.com> > Cc: Ramesh Thomas <ramesh.thomas@intel.com> > Cc: Mel Gorman <mgorman@suse.de> > Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> I agree that removing this is the most sensible option so; Acked-by: Mel Gorman <mgorman@suse.de> -- Mel Gorman SUSE Labs
On Thu, Oct 4, 2018 at 2:04 PM Daniel Lezcano <daniel.lezcano@linaro.org> wrote: > > The function get_loadavg() returns almost always zero. To be more > precise, statistically speaking for a total of 1023379 times passing > in the function, the load is equal to zero 1020728 times, greater than > 100, 610 times, the remaining is between 0 and 5. > > In 2011, the get_loadavg() was removed from the Android tree because > of the above [1]. At this time, the load was: > > unsigned long this_cpu_load(void) > { > struct rq *this = this_rq(); > return this->cpu_load[0]; > } > > In 2014, the code was changed by commit 372ba8cb46b2 (cpuidle: menu: Lookup CPU > runqueues less) and the load is: > > void get_iowait_load(unsigned long *nr_waiters, unsigned long *load) > { > struct rq *rq = this_rq(); > *nr_waiters = atomic_read(&rq->nr_iowait); > *load = rq->load.weight; > } > > with the same result. > > Both measurements show using the load in this code path does no matter > anymore. Removing it. > > [1] https://android.googlesource.com/kernel/common/+/4dedd9f124703207895777ac6e91dacde0f7cc17 > > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Todd Kjos <tkjos@google.com> > Cc: Joel Fernandes <joelaf@google.com> > Cc: Colin Cross <ccross@android.com> > Cc: Ramesh Thomas <ramesh.thomas@intel.com> > Cc: Mel Gorman <mgorman@suse.de> > Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > drivers/cpuidle/governors/menu.c | 26 +++++++------------------- > include/linux/sched/stat.h | 1 - > kernel/sched/core.c | 7 ------- > 3 files changed, 7 insertions(+), 27 deletions(-) > > diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c > index e26a409..066b01f 100644 > --- a/drivers/cpuidle/governors/menu.c > +++ b/drivers/cpuidle/governors/menu.c > @@ -135,11 +135,6 @@ struct menu_device { > #define LOAD_INT(x) ((x) >> FSHIFT) > #define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100) > > -static inline int get_loadavg(unsigned long load) > -{ > - return LOAD_INT(load) * 10 + LOAD_FRAC(load) / 10; > -} > - > static inline int which_bucket(unsigned int duration, unsigned long nr_iowaiters) > { > int bucket = 0; > @@ -173,18 +168,10 @@ static inline int which_bucket(unsigned int duration, unsigned long nr_iowaiters > * to be, the higher this multiplier, and thus the higher > * the barrier to go to an expensive C state. > */ > -static inline int performance_multiplier(unsigned long nr_iowaiters, unsigned long load) > +static inline int performance_multiplier(unsigned long nr_iowaiters) > { > - int mult = 1; > - > - /* for higher loadavg, we are more reluctant */ > - > - mult += 2 * get_loadavg(load); > - > - /* for IO wait tasks (per cpu!) we add 5x each */ > - mult += 10 * nr_iowaiters; > - > - return mult; > + /* for IO wait tasks (per cpu!) we add 10x each */ > + return 1 + 10 * nr_iowaiters; > } > > static DEFINE_PER_CPU(struct menu_device, menu_devices); > @@ -290,7 +277,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, > int idx; > unsigned int interactivity_req; > unsigned int expected_interval; > - unsigned long nr_iowaiters, cpu_load; > + unsigned long nr_iowaiters; > ktime_t delta_next; > > if (data->needs_update) { > @@ -307,7 +294,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, > /* determine the expected residency time, round up */ > data->next_timer_us = ktime_to_us(tick_nohz_get_sleep_length(&delta_next)); > > - get_iowait_load(&nr_iowaiters, &cpu_load); > + nr_iowaiters = nr_iowait_cpu(dev->cpu); > data->bucket = which_bucket(data->next_timer_us, nr_iowaiters); > > /* > @@ -359,7 +346,8 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, > * Use the performance multiplier and the user-configurable > * latency_req to determine the maximum exit latency. > */ > - interactivity_req = data->predicted_us / performance_multiplier(nr_iowaiters, cpu_load); > + interactivity_req = data->predicted_us / > + performance_multiplier(nr_iowaiters); > if (latency_req > interactivity_req) > latency_req = interactivity_req; > } > diff --git a/include/linux/sched/stat.h b/include/linux/sched/stat.h > index 04f1321..f30954c 100644 > --- a/include/linux/sched/stat.h > +++ b/include/linux/sched/stat.h > @@ -20,7 +20,6 @@ extern unsigned long nr_running(void); > extern bool single_task_running(void); > extern unsigned long nr_iowait(void); > extern unsigned long nr_iowait_cpu(int cpu); > -extern void get_iowait_load(unsigned long *nr_waiters, unsigned long *load); > > static inline int sched_info_on(void) > { > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 43efb74..48a786a 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -2886,13 +2886,6 @@ unsigned long nr_iowait_cpu(int cpu) > return atomic_read(&cpu_rq(cpu)->nr_iowait); > } > > -void get_iowait_load(unsigned long *nr_waiters, unsigned long *load) > -{ > - struct rq *rq = this_rq(); > - *nr_waiters = atomic_read(&rq->nr_iowait); > - *load = rq->load.weight; > -} > - > /* > * IO-wait accounting, and how its mostly bollocks (on SMP). > * > -- > 2.7.4 >
On Thu, Oct 04, 2018 at 02:04:02PM +0200, Daniel Lezcano wrote: > The function nr_iowait_cpu() can be used directly by nr_iowait() instead > of duplicating code. > > Call nr_iowait_cpu() from nr_iowait() > > Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
On Thu, Oct 04, 2018 at 02:04:03PM +0200, Daniel Lezcano wrote: > The function get_loadavg() returns almost always zero. To be more > precise, statistically speaking for a total of 1023379 times passing > in the function, the load is equal to zero 1020728 times, greater than > 100, 610 times, the remaining is between 0 and 5. > > In 2011, the get_loadavg() was removed from the Android tree because > of the above [1]. At this time, the load was: > > unsigned long this_cpu_load(void) > { > struct rq *this = this_rq(); > return this->cpu_load[0]; > } > > In 2014, the code was changed by commit 372ba8cb46b2 (cpuidle: menu: Lookup CPU > runqueues less) and the load is: > > void get_iowait_load(unsigned long *nr_waiters, unsigned long *load) > { > struct rq *rq = this_rq(); > *nr_waiters = atomic_read(&rq->nr_iowait); > *load = rq->load.weight; > } > > with the same result. > > Both measurements show using the load in this code path does no matter > anymore. Removing it. > > [1] https://android.googlesource.com/kernel/common/+/4dedd9f124703207895777ac6e91dacde0f7cc17 > > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Todd Kjos <tkjos@google.com> > Cc: Joel Fernandes <joelaf@google.com> > Cc: Colin Cross <ccross@android.com> > Cc: Ramesh Thomas <ramesh.thomas@intel.com> > Cc: Mel Gorman <mgorman@suse.de> > Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
On Thursday, October 4, 2018 2:04:02 PM CEST Daniel Lezcano wrote: > The function nr_iowait_cpu() can be used directly by nr_iowait() instead > of duplicating code. > > Call nr_iowait_cpu() from nr_iowait() > > Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> > --- > kernel/sched/core.c | 41 ++++++++++++++++++++--------------------- > 1 file changed, 20 insertions(+), 21 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 625bc98..43efb74 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -2875,6 +2875,25 @@ unsigned long long nr_context_switches(void) > } > > /* > + * Consumers of these two interfaces, like for example the cpufreq menu > + * governor are using nonsensical data. Boosting frequency for a CPU that has > + * IO-wait which might not even end up running the task when it does become > + * runnable. > + */ > + > +unsigned long nr_iowait_cpu(int cpu) > +{ > + return atomic_read(&cpu_rq(cpu)->nr_iowait); > +} > + > +void get_iowait_load(unsigned long *nr_waiters, unsigned long *load) > +{ > + struct rq *rq = this_rq(); > + *nr_waiters = atomic_read(&rq->nr_iowait); > + *load = rq->load.weight; > +} > + > +/* > * IO-wait accounting, and how its mostly bollocks (on SMP). > * > * The idea behind IO-wait account is to account the idle time that we could > @@ -2909,31 +2928,11 @@ unsigned long nr_iowait(void) > unsigned long i, sum = 0; > > for_each_possible_cpu(i) > - sum += atomic_read(&cpu_rq(i)->nr_iowait); > + sum += nr_iowait_cpu(i); > > return sum; > } > > -/* > - * Consumers of these two interfaces, like for example the cpufreq menu > - * governor are using nonsensical data. Boosting frequency for a CPU that has > - * IO-wait which might not even end up running the task when it does become > - * runnable. > - */ > - > -unsigned long nr_iowait_cpu(int cpu) > -{ > - struct rq *this = cpu_rq(cpu); > - return atomic_read(&this->nr_iowait); > -} > - > -void get_iowait_load(unsigned long *nr_waiters, unsigned long *load) > -{ > - struct rq *rq = this_rq(); > - *nr_waiters = atomic_read(&rq->nr_iowait); > - *load = rq->load.weight; > -} > - > #ifdef CONFIG_SMP > > /* > Both [1-2/2] applied with Peter's ACKs, thanks!
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 625bc98..43efb74 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2875,6 +2875,25 @@ unsigned long long nr_context_switches(void) } /* + * Consumers of these two interfaces, like for example the cpufreq menu + * governor are using nonsensical data. Boosting frequency for a CPU that has + * IO-wait which might not even end up running the task when it does become + * runnable. + */ + +unsigned long nr_iowait_cpu(int cpu) +{ + return atomic_read(&cpu_rq(cpu)->nr_iowait); +} + +void get_iowait_load(unsigned long *nr_waiters, unsigned long *load) +{ + struct rq *rq = this_rq(); + *nr_waiters = atomic_read(&rq->nr_iowait); + *load = rq->load.weight; +} + +/* * IO-wait accounting, and how its mostly bollocks (on SMP). * * The idea behind IO-wait account is to account the idle time that we could @@ -2909,31 +2928,11 @@ unsigned long nr_iowait(void) unsigned long i, sum = 0; for_each_possible_cpu(i) - sum += atomic_read(&cpu_rq(i)->nr_iowait); + sum += nr_iowait_cpu(i); return sum; } -/* - * Consumers of these two interfaces, like for example the cpufreq menu - * governor are using nonsensical data. Boosting frequency for a CPU that has - * IO-wait which might not even end up running the task when it does become - * runnable. - */ - -unsigned long nr_iowait_cpu(int cpu) -{ - struct rq *this = cpu_rq(cpu); - return atomic_read(&this->nr_iowait); -} - -void get_iowait_load(unsigned long *nr_waiters, unsigned long *load) -{ - struct rq *rq = this_rq(); - *nr_waiters = atomic_read(&rq->nr_iowait); - *load = rq->load.weight; -} - #ifdef CONFIG_SMP /*