cpufreq: schedutil: Use idle_calls counter of the remote CPU
Subsystems (3)
PATCH 1/3 cpufreq: schedutil: Use idle_calls counter of the remote CPU
Since the recent remote cpufreq callback work, its possible that a cpufreq update is triggered from a remote CPU. For single policies however, the current code uses the local CPU when trying to determine if the remote sg_cpu entered idle or is busy. This is incorrect. To remedy this, compare with the nohz tick idle_calls counter of the remote CPU.
--- include/linux/tick.h | 1 + kernel/sched/cpufreq_schedutil.c | 2 +- kernel/time/tick-sched.c | 13 +++++++++++++ 3 files changed, 15 insertions(+), 1 deletion(-)
include/linux/tick.h +1 -0
@@ -119,6 +119,7 @@ extern void tick_nohz_idle_exit(void);extern void tick_nohz_irq_exit (void );extern ktime_t tick_nohz_get_sleep_length (void );extern unsigned long tick_nohz_get_idle_calls (void ); +extern unsigned long tick_nohz_get_idle_calls_cpu (int cpu);extern u64 get_cpu_idle_time_us (int cpu,u64 *last_update_time);extern u64 get_cpu_iowait_time_us (int cpu,u64 *last_update_time);#else /* !CONFIG_NO_HZ_COMMON */
kernel/sched/cpufreq_schedutil.c +1 -1
@@ -244,7 +244,7 @@ static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, unsigned long *util,#ifdef CONFIG_NO_HZ_COMMON static bool sugov_cpu_is_busy (struct sugov_cpu *sg_cpu) { -unsigned long idle_calls =tick_nohz_get_idle_calls (); +unsigned long idle_calls =tick_nohz_get_idle_calls_cpu (sg_cpu->cpu);bool ret = idle_calls == sg_cpu->saved_idle_calls; sg_cpu->saved_idle_calls = idle_calls;
kernel/time/tick-sched.c +13 -0
@@ -985,6 +985,19 @@ ktime_t tick_nohz_get_sleep_length(void)return ts->sleep_length; } +/** +* tick_nohz_get_idle_calls_cpu - return the current idle calls counter value +* for a particular CPU. +* +* Called from the schedutil frequency scaling governor in scheduler context. +*/ +unsigned long tick_nohz_get_idle_calls_cpu (int cpu) +{ +struct tick_sched *ts =tick_get_tick_sched (cpu); + +return ts->idle_calls; +} +/** * tick_nohz_get_idle_calls - return the current idle calls counter value *
Signature · 1 line
2.15.1.504.g5279b80103-goog
PATCH 2/3 sched/fair: Correct obsolete comment about cpufreq_update_util
Since the remote cpufreq callback work, the cpufreq_update_util call can happen from remote CPUs. The comment about local CPUs is thus obsolete. Update it accordingly.
--- kernel/sched/fair.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
kernel/sched/fair.c +1 -3
@@ -3020,9 +3020,7 @@ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)/* * There are a few boundary cases this might miss but it should * get called often enough that that should (hopefully) not be -* a real problem -- added to that it only calls on the local -* CPU, so if we enqueue remotely we'll miss an update, but -* the next tick/schedule should update. +* a real problem. * * It will not get called when we go idle, because the idle * thread is a different class (!fair), nor will the utilization
Signature · 1 line
2.15.1.504.g5279b80103-goog
Peter Zijlstra
maintainerRe: [PATCH 2/3] sched/fair: Correct obsolete comment about cpufreq_update_util
Quoted 6 lines · Joel Fernandes
Since the remote cpufreq callback work, the
cpufreq_update_utilcall can happen from remote CPUs. The comment about local CPUs is thus obsolete. Update it accordingly.Reviewed-by Viresh Kumar <[email protected]>Signed-off-by Joel Fernandes <[email protected]>
Sure, ACK
Quoted 22 lines
--- kernel/sched/fair.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)kernel/sched/fair.c +1
-3@@ -3020,9 +3020,7 @@ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)/* * There are a few boundary cases this might miss but it should * get called often enough that that should (hopefully) not be -* a real problem -- added to that it only calls on the local -* CPU, so if we enqueue remotely we'll miss an update, but -* the next tick/schedule should update. +* a real problem. * * It will not get called when we go idle, because the idle * thread is a different class (!fair), nor will the utilization Signature · 1 line
2.15.1.504.g5279b80103-goog
tip-bot for Joel Fernandes
merge bot[tip:sched/core] sched/fair: Correct obsolete comment about cpufreq_update_util()
In reply to Joel Fernandessched/fair: Correct obsolete comment about cpufreq_update_util()
Commit-ID: 9783be2c0e90bbaceec3c471c4fb017bff7293ba Gitweb: https://git.kernel.org/tip/9783be2c0e90bbaceec3c471c4fb017bff7293ba Author: Joel Fernandes <[email protected]> AuthorDate: Fri, 15 Dec 2017 07:39:43 -0800 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 10 Jan 2018 11:30:30 +0100
sched/fair: Correct obsolete comment about cpufreq_update_util()
Since the remote cpufreq callback work, the cpufreq_update_util() call can happen from remote CPUs. The comment about local CPUs is thus obsolete. Update it accordingly.
--- kernel/sched/fair.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
kernel/sched/fair.c +1 -3
@@ -3020,9 +3020,7 @@ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)/* * There are a few boundary cases this might miss but it should * get called often enough that that should (hopefully) not be -* a real problem -- added to that it only calls on the local -* CPU, so if we enqueue remotely we'll miss an update, but -* the next tick/schedule should update. +* a real problem. * * It will not get called when we go idle, because the idle * thread is a different class (!fair), nor will the utilization
PATCH 3/3 sched/fair: remove impossible condition from find_idlest_group_cpu
In reply to Joel Fernandesfind_idlest_group_cpu goes through CPUs of a group previous selected by find_idlest_group. find_idlest_group returns NULL if the local group is the selected one and doesn't execute find_idlest_group_cpu if the group to which 'cpu' belongs to is chosen. So we're always guaranteed to call find_idlest_group_cpu with a group to which cpu is non-local. This makes one of the conditions in find_idlest_group_cpu an impossible one, which we can get rid off.
--- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
kernel/sched/fair.c +1 -1
@@ -5948,7 +5948,7 @@ find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this } }else if (shallowest_idle_cpu ==-1 ) { load =weighted_cpuload (cpu_rq (i)); -if (load < min_load || (load == min_load && i == this_cpu)) { +if (load < min_load) { min_load = load; least_loaded_cpu = i; }
Signature · 1 line
2.15.1.504.g5279b80103-goog
tip-bot for Joel Fernandes
merge bot[tip:sched/core] sched/fair: Remove impossible condition from find_idlest_group_cpu()
sched/fair: Remove impossible condition from find_idlest_group_cpu()
Commit-ID: 18cec7e0ddd5e28b7722f7049d715873373be3e9 Gitweb: https://git.kernel.org/tip/18cec7e0ddd5e28b7722f7049d715873373be3e9 Author: Joel Fernandes <[email protected]> AuthorDate: Fri, 15 Dec 2017 07:39:44 -0800 Committer: Ingo Molnar <[email protected]> CommitDate: Wed, 10 Jan 2018 11:30:30 +0100
sched/fair: Remove impossible condition from find_idlest_group_cpu()
find_idlest_group_cpu() goes through CPUs of a group previous selected by find_idlest_group(). find_idlest_group() returns NULL if the local group is the selected one and doesn't execute find_idlest_group_cpu if the group to which 'cpu' belongs to is chosen. So we're always guaranteed to call find_idlest_group_cpu() with a group to which 'cpu' is non-local.
This makes one of the conditions in find_idlest_group_cpu() an impossible one, which we can get rid off.
--- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
kernel/sched/fair.c +1 -1
@@ -5950,7 +5950,7 @@ find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this } }else if (shallowest_idle_cpu ==-1 ) { load =weighted_cpuload (cpu_rq (i)); -if (load < min_load || (load == min_load && i == this_cpu)) { +if (load < min_load) { min_load = load; least_loaded_cpu = i; }