From 3dc167ba5729ddd2d8e3fa1841653792c295d3f1 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 19 May 2020 19:25:06 +0200 Subject: sched/cputime: Improve cputime_adjust() People report that utime and stime from /proc//stat become very wrong when the numbers are big enough, especially if you watch these counters incrementally. Specifically, the current implementation of: stime*rtime/total, results in a saw-tooth function on top of the desired line, where the teeth grow in size the larger the values become. IOW, it has a relative error. The result is that, when watching incrementally as time progresses (for large values), we'll see periods of pure stime or utime increase, irrespective of the actual ratio we're striving for. Replace scale_stime() with a math64.h helper: mul_u64_u64_div_u64() that is far more accurate. This also allows architectures to override the implementation -- for instance they can opt for the old algorithm if this new one turns out to be too expensive for them. Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200519172506.GA317395@hirez.programming.kicks-ass.net --- include/linux/math64.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux') diff --git a/include/linux/math64.h b/include/linux/math64.h index 11a267413e8e..d097119419e6 100644 --- a/include/linux/math64.h +++ b/include/linux/math64.h @@ -263,6 +263,8 @@ static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 divisor) } #endif /* mul_u64_u32_div */ +u64 mul_u64_u64_div_u64(u64 a, u64 mul, u64 div); + #define DIV64_U64_ROUND_UP(ll, d) \ ({ u64 _tmp = (d); div64_u64((ll) + _tmp - 1, _tmp); }) -- cgit v1.2.3 From 461daba06bdcb9c7a3f92b9bbd110e1f7d093ffc Mon Sep 17 00:00:00 2001 From: Suren Baghdasaryan Date: Thu, 28 May 2020 12:54:42 -0700 Subject: psi: eliminate kthread_worker from psi trigger scheduling mechanism Each psi group requires a dedicated kthread_delayed_work and kthread_worker. Since no other work can be performed using psi_group's kthread_worker, the same result can be obtained using a task_struct and a timer directly. This makes psi triggering simpler by removing lists and locks involved with kthread_worker usage and eliminates the need for poll_scheduled atomic use in the hot path. Signed-off-by: Suren Baghdasaryan Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200528195442.190116-1-surenb@google.com --- include/linux/psi_types.h | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/psi_types.h b/include/linux/psi_types.h index 4b7258495a04..b95f3211566a 100644 --- a/include/linux/psi_types.h +++ b/include/linux/psi_types.h @@ -153,9 +153,10 @@ struct psi_group { unsigned long avg[NR_PSI_STATES - 1][3]; /* Monitor work control */ - atomic_t poll_scheduled; - struct kthread_worker __rcu *poll_kworker; - struct kthread_delayed_work poll_work; + struct task_struct __rcu *poll_task; + struct timer_list poll_timer; + wait_queue_head_t poll_wait; + atomic_t poll_wakeup; /* Protects data used by the monitor */ struct mutex trigger_lock; -- cgit v1.2.3 From 9cc5b8656892a72438ee7deb5e80f5be47643b8b Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Wed, 27 May 2020 16:29:09 +0200 Subject: isolcpus: Affine unbound kernel threads to housekeeping cpus This is a kernel enhancement that configures the cpu affinity of kernel threads via kernel boot option nohz_full=. When this option is specified, the cpumask is immediately applied upon kthread launch. This does not affect kernel threads that specify cpu and node. This allows CPU isolation (that is not allowing certain threads to execute on certain CPUs) without using the isolcpus=domain parameter, making it possible to enable load balancing on such CPUs during runtime (see kernel-parameters.txt). Note-1: this is based off on Wind River's patch at https://github.com/starlingx-staging/stx-integ/blob/master/kernel/kernel-std/centos/patches/affine-compute-kernel-threads.patch Difference being that this patch is limited to modifying kernel thread cpumask. Behaviour of other threads can be controlled via cgroups or sched_setaffinity. Note-2: Wind River's patch was based off Christoph Lameter's patch at https://lwn.net/Articles/565932/ with the only difference being the kernel parameter changed from kthread to kthread_cpus. Signed-off-by: Frederic Weisbecker Signed-off-by: Marcelo Tosatti Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200527142909.23372-3-frederic@kernel.org --- include/linux/sched/isolation.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux') diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h index 0fbcbacd1b29..cc9f393e2a70 100644 --- a/include/linux/sched/isolation.h +++ b/include/linux/sched/isolation.h @@ -14,6 +14,7 @@ enum hk_flags { HK_FLAG_DOMAIN = (1 << 5), HK_FLAG_WQ = (1 << 6), HK_FLAG_MANAGED_IRQ = (1 << 7), + HK_FLAG_KTHREAD = (1 << 8), }; #ifdef CONFIG_CPU_ISOLATION -- cgit v1.2.3 From b4098bfc5efb1fd7ecf40165132a1283aeea3500 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 26 Jul 2019 16:54:10 +0200 Subject: sched/deadline: Impose global limits on sched_attr::sched_period Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20190726161357.397880775@infradead.org --- include/linux/sched/sysctl.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux') diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h index 660ac49f2b53..24be30a40814 100644 --- a/include/linux/sched/sysctl.h +++ b/include/linux/sched/sysctl.h @@ -61,6 +61,9 @@ int sched_proc_update_handler(struct ctl_table *table, int write, extern unsigned int sysctl_sched_rt_period; extern int sysctl_sched_rt_runtime; +extern unsigned int sysctl_sched_dl_period_max; +extern unsigned int sysctl_sched_dl_period_min; + #ifdef CONFIG_UCLAMP_TASK extern unsigned int sysctl_sched_uclamp_util_min; extern unsigned int sysctl_sched_uclamp_util_max; -- cgit v1.2.3 From 01e377c539ca52a6c753d0fdbe93b3b8fcd66a1c Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Thu, 18 Jun 2020 21:08:10 +0200 Subject: sched/core: Remove mmdrop() definition Commit bf2c59fce4074 ("sched/core: Fix illegal RCU from offline CPUs") introduced a definition for mmdrop() but a a few lines above there is already mmdrop() defined as static inline. Remove the newly introduced mmdrop() definition. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200618190810.790211-1-bigeasy@linutronix.de --- include/linux/sched/mm.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index 480a4d1b7dd8..a98604ea76f1 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -49,8 +49,6 @@ static inline void mmdrop(struct mm_struct *mm) __mmdrop(mm); } -void mmdrop(struct mm_struct *mm); - /* * This has to be called after a get_task_mm()/mmget_not_zero() * followed by taking the mmap_lock for writing before modifying the -- cgit v1.2.3 From 9d246053a69196c7c27068870e9b4b66ac536f68 Mon Sep 17 00:00:00 2001 From: Phil Auld Date: Mon, 29 Jun 2020 15:23:03 -0400 Subject: sched: Add a tracepoint to track rq->nr_running Add a bare tracepoint trace_sched_update_nr_running_tp which tracks ->nr_running CPU's rq. This is used to accurately trace this data and provide a visualization of scheduler imbalances in, for example, the form of a heat map. The tracepoint is accessed by loading an external kernel module. An example module (forked from Qais' module and including the pelt related tracepoints) can be found at: https://github.com/auldp/tracepoints-helpers.git A script to turn the trace-cmd report output into a heatmap plot can be found at: https://github.com/jirvoz/plot-nr-running The tracepoints are added to add_nr_running() and sub_nr_running() which are in kernel/sched/sched.h. In order to avoid CREATE_TRACE_POINTS in the header a wrapper call is used and the trace/events/sched.h include is moved before sched.h in kernel/sched/core. Signed-off-by: Phil Auld Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200629192303.GC120228@lorien.usersys.redhat.com --- include/linux/sched.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux') diff --git a/include/linux/sched.h b/include/linux/sched.h index 683372943093..12b10ce51a08 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2044,6 +2044,7 @@ const struct sched_avg *sched_trace_rq_avg_dl(struct rq *rq); const struct sched_avg *sched_trace_rq_avg_irq(struct rq *rq); int sched_trace_rq_cpu(struct rq *rq); +int sched_trace_rq_nr_running(struct rq *rq); const struct cpumask *sched_trace_rd_span(struct root_domain *rd); -- cgit v1.2.3 From 58877d347b58c9e971112df5eb311c13bb0acb28 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 2 Jul 2020 14:52:11 +0200 Subject: sched: Better document ttwu() Dave hit the problem fixed by commit: b6e13e85829f ("sched/core: Fix ttwu() race") and failed to understand much of the code involved. Per his request a few comments to (hopefully) clarify things. Requested-by: Dave Chinner Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200702125211.GQ4800@hirez.programming.kicks-ass.net --- include/linux/sched.h | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) (limited to 'include/linux') diff --git a/include/linux/sched.h b/include/linux/sched.h index 12b10ce51a08..5033813fecd5 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -154,24 +154,24 @@ struct task_group; * * for (;;) { * set_current_state(TASK_UNINTERRUPTIBLE); - * if (!need_sleep) - * break; + * if (CONDITION) + * break; * * schedule(); * } * __set_current_state(TASK_RUNNING); * * If the caller does not need such serialisation (because, for instance, the - * condition test and condition change and wakeup are under the same lock) then + * CONDITION test and condition change and wakeup are under the same lock) then * use __set_current_state(). * * The above is typically ordered against the wakeup, which does: * - * need_sleep = false; + * CONDITION = 1; * wake_up_state(p, TASK_UNINTERRUPTIBLE); * - * where wake_up_state() executes a full memory barrier before accessing the - * task state. + * where wake_up_state()/try_to_wake_up() executes a full memory barrier before + * accessing p->state. * * Wakeup will do: if (@state & p->state) p->state = TASK_RUNNING, that is, * once it observes the TASK_UNINTERRUPTIBLE store the waking CPU can issue a -- cgit v1.2.3 From 46132e3ac58cb2ee48051ed80bffc0070ad59b2e Mon Sep 17 00:00:00 2001 From: Paul Gortmaker Date: Wed, 1 Jul 2020 14:34:18 -0400 Subject: sched: nohz: stop passing around unused "ticks" parameter. The "ticks" parameter was added in commit 0f004f5a696a ("sched: Cure more NO_HZ load average woes") since calc_global_nohz() was called and needed the "ticks" argument. But in commit c308b56b5398 ("sched: Fix nohz load accounting -- again!") it became unused as the function calc_global_nohz() dropped using "ticks". Fixes: c308b56b5398 ("sched: Fix nohz load accounting -- again!") Signed-off-by: Paul Gortmaker Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/1593628458-32290-1-git-send-email-paul.gortmaker@windriver.com --- include/linux/sched/loadavg.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/sched/loadavg.h b/include/linux/sched/loadavg.h index 4859bea47a7b..83ec54b65e79 100644 --- a/include/linux/sched/loadavg.h +++ b/include/linux/sched/loadavg.h @@ -43,6 +43,6 @@ extern unsigned long calc_load_n(unsigned long load, unsigned long exp, #define LOAD_INT(x) ((x) >> FSHIFT) #define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100) -extern void calc_global_load(unsigned long ticks); +extern void calc_global_load(void); #endif /* _LINUX_SCHED_LOADAVG_H */ -- cgit v1.2.3 From e0078e2eb8620079d988f150ba02a4ce9b5a946a Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Wed, 15 Jul 2020 18:30:31 -0700 Subject: linux/sched/mm.h: drop duplicated words in comments Drop doubled words "to" and "that". Signed-off-by: Randy Dunlap Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/927ea8d8-3f6c-9b65-4c2b-63ab4bd59ef1@infradead.org --- include/linux/sched/mm.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index a98604ea76f1..6be66f52a2ad 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -23,7 +23,7 @@ extern struct mm_struct *mm_alloc(void); * will still exist later on and mmget_not_zero() has to be used before * accessing it. * - * This is a preferred way to to pin @mm for a longer/unbounded amount + * This is a preferred way to pin @mm for a longer/unbounded amount * of time. * * Use mmdrop() to release the reference acquired by mmgrab(). @@ -232,7 +232,7 @@ static inline unsigned int memalloc_noio_save(void) * @flags: Flags to restore. * * Ends the implicit GFP_NOIO scope started by memalloc_noio_save function. - * Always make sure that that the given flags is the return value from the + * Always make sure that the given flags is the return value from the * pairing memalloc_noio_save call. */ static inline void memalloc_noio_restore(unsigned int flags) @@ -263,7 +263,7 @@ static inline unsigned int memalloc_nofs_save(void) * @flags: Flags to restore. * * Ends the implicit GFP_NOFS scope started by memalloc_nofs_save function. - * Always make sure that that the given flags is the return value from the + * Always make sure that the given flags is the return value from the * pairing memalloc_nofs_save call. */ static inline void memalloc_nofs_restore(unsigned int flags) -- cgit v1.2.3 From 25980c7a79af42f2daa73e2f475ebf4cbac8253e Mon Sep 17 00:00:00 2001 From: Valentin Schneider Date: Sun, 12 Jul 2020 17:59:15 +0100 Subject: arch_topology, sched/core: Cleanup thermal pressure definition The following commit: 14533a16c46d ("thermal/cpu-cooling, sched/core: Move the arch_set_thermal_pressure() API to generic scheduler code") moved the definition of arch_set_thermal_pressure() to sched/core.c, but kept its declaration in linux/arch_topology.h. When building e.g. an x86 kernel with CONFIG_SCHED_THERMAL_PRESSURE=y, cpufreq_cooling.c ends up getting the declaration of arch_set_thermal_pressure() from include/linux/arch_topology.h, which is somewhat awkward. On top of this, sched/core.c unconditionally defines o The thermal_pressure percpu variable o arch_set_thermal_pressure() while arch_scale_thermal_pressure() does nothing unless redefined by the architecture. arch_*() functions are meant to be defined by architectures, so revert the aforementioned commit and re-implement it in a way that keeps arch_set_thermal_pressure() architecture-definable, and doesn't define the thermal pressure percpu variable for kernels that don't need it (CONFIG_SCHED_THERMAL_PRESSURE=n). Signed-off-by: Valentin Schneider Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200712165917.9168-2-valentin.schneider@arm.com --- include/linux/arch_topology.h | 4 ++-- include/linux/sched/topology.h | 7 +++++++ 2 files changed, 9 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h index 0566cb3314ef..69b1dabe39dc 100644 --- a/include/linux/arch_topology.h +++ b/include/linux/arch_topology.h @@ -39,8 +39,8 @@ static inline unsigned long topology_get_thermal_pressure(int cpu) return per_cpu(thermal_pressure, cpu); } -void arch_set_thermal_pressure(struct cpumask *cpus, - unsigned long th_pressure); +void topology_set_thermal_pressure(const struct cpumask *cpus, + unsigned long th_pressure); struct cpu_topology { int thread_id; diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h index fb11091129b3..764222d637b7 100644 --- a/include/linux/sched/topology.h +++ b/include/linux/sched/topology.h @@ -232,6 +232,13 @@ unsigned long arch_scale_thermal_pressure(int cpu) } #endif +#ifndef arch_set_thermal_pressure +static __always_inline +void arch_set_thermal_pressure(const struct cpumask *cpus, + unsigned long th_pressure) +{ } +#endif + static inline int task_node(const struct task_struct *p) { return cpu_to_node(task_cpu(p)); -- cgit v1.2.3 From c1b7b8d42b5422627b0a8268416a60748f8d000f Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E7=8E=8B=E6=96=87=E8=99=8E?= Date: Mon, 27 Jul 2020 21:39:51 +0800 Subject: sched: Fix a typo in a comment Change the comment typo: "direcly" -> "directly". Signed-off-by: Wang Wenhu Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/AAcAXwBTDSpsKN-5iyIOtaqk.1.1595857191899.Hmail.wenhu.wang@vivo.com --- include/linux/sched.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/sched.h b/include/linux/sched.h index 5033813fecd5..adf0125190d4 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -374,7 +374,7 @@ struct util_est { * For cfs_rq, they are the aggregated values of all runnable and blocked * sched_entities. * - * The load/runnable/util_avg doesn't direcly factor frequency scaling and CPU + * The load/runnable/util_avg doesn't directly factor frequency scaling and CPU * capacity scaling. The scaling is done through the rq_clock_pelt that is used * for computing those signals (see update_rq_clock_pelt()) * -- cgit v1.2.3 From 13685c4a08fca9dd76bf53bfcbadc044ab2a08cb Mon Sep 17 00:00:00 2001 From: Qais Yousef Date: Thu, 16 Jul 2020 12:03:45 +0100 Subject: sched/uclamp: Add a new sysctl to control RT default boost value RT tasks by default run at the highest capacity/performance level. When uclamp is selected this default behavior is retained by enforcing the requested uclamp.min (p->uclamp_req[UCLAMP_MIN]) of the RT tasks to be uclamp_none(UCLAMP_MAX), which is SCHED_CAPACITY_SCALE; the maximum value. This is also referred to as 'the default boost value of RT tasks'. See commit 1a00d999971c ("sched/uclamp: Set default clamps for RT tasks"). On battery powered devices, it is desired to control this default (currently hardcoded) behavior at runtime to reduce energy consumed by RT tasks. For example, a mobile device manufacturer where big.LITTLE architecture is dominant, the performance of the little cores varies across SoCs, and on high end ones the big cores could be too power hungry. Given the diversity of SoCs, the new knob allows manufactures to tune the best performance/power for RT tasks for the particular hardware they run on. They could opt to further tune the value when the user selects a different power saving mode or when the device is actively charging. The runtime aspect of it further helps in creating a single kernel image that can be run on multiple devices that require different tuning. Keep in mind that a lot of RT tasks in the system are created by the kernel. On Android for instance I can see over 50 RT tasks, only a handful of which created by the Android framework. To control the default behavior globally by system admins and device integrator, introduce the new sysctl_sched_uclamp_util_min_rt_default to change the default boost value of the RT tasks. I anticipate this to be mostly in the form of modifying the init script of a particular device. To avoid polluting the fast path with unnecessary code, the approach taken is to synchronously do the update by traversing all the existing tasks in the system. This could race with a concurrent fork(), which is dealt with by introducing sched_post_fork() function which will ensure the racy fork will get the right update applied. Tested on Juno-r2 in combination with the RT capacity awareness [1]. By default an RT task will go to the highest capacity CPU and run at the maximum frequency, which is particularly energy inefficient on high end mobile devices because the biggest core[s] are 'huge' and power hungry. With this patch the RT task can be controlled to run anywhere by default, and doesn't cause the frequency to be maximum all the time. Yet any task that really needs to be boosted can easily escape this default behavior by modifying its requested uclamp.min value (p->uclamp_req[UCLAMP_MIN]) via sched_setattr() syscall. [1] 804d402fb6f6: ("sched/rt: Make RT capacity-aware") Signed-off-by: Qais Yousef Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200716110347.19553-2-qais.yousef@arm.com --- include/linux/sched.h | 10 ++++++++-- include/linux/sched/sysctl.h | 1 + include/linux/sched/task.h | 1 + 3 files changed, 10 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/sched.h b/include/linux/sched.h index adf0125190d4..a6bf77c34687 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -686,9 +686,15 @@ struct task_struct { struct sched_dl_entity dl; #ifdef CONFIG_UCLAMP_TASK - /* Clamp values requested for a scheduling entity */ + /* + * Clamp values requested for a scheduling entity. + * Must be updated with task_rq_lock() held. + */ struct uclamp_se uclamp_req[UCLAMP_CNT]; - /* Effective clamp values used for a scheduling entity */ + /* + * Effective clamp values used for a scheduling entity. + * Must be updated with task_rq_lock() held. + */ struct uclamp_se uclamp[UCLAMP_CNT]; #endif diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h index 24be30a40814..3c31ba88aca5 100644 --- a/include/linux/sched/sysctl.h +++ b/include/linux/sched/sysctl.h @@ -67,6 +67,7 @@ extern unsigned int sysctl_sched_dl_period_min; #ifdef CONFIG_UCLAMP_TASK extern unsigned int sysctl_sched_uclamp_util_min; extern unsigned int sysctl_sched_uclamp_util_max; +extern unsigned int sysctl_sched_uclamp_util_min_rt_default; #endif #ifdef CONFIG_CFS_BANDWIDTH diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index 38359071236a..e7ddab095baf 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -55,6 +55,7 @@ extern asmlinkage void schedule_tail(struct task_struct *prev); extern void init_idle(struct task_struct *idle, int cpu); extern int sched_fork(unsigned long clone_flags, struct task_struct *p); +extern void sched_post_fork(struct task_struct *p); extern void sched_dead(struct task_struct *p); void __noreturn do_task_dead(void); -- cgit v1.2.3 From f4470cdf108f00533e8079b19434e6cb48c17fa3 Mon Sep 17 00:00:00 2001 From: Valentin Schneider Date: Fri, 31 Jul 2020 20:20:14 +0100 Subject: sched: Document arch_scale_*_capacity() Rather that hide their purpose in some dark, damp corner of Documentation/, add some documentation to the default implementations. Signed-off-by: Valentin Schneider Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20200731192016.7484-2-valentin.schneider@arm.com --- include/linux/sched/topology.h | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'include/linux') diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h index 764222d637b7..820511289857 100644 --- a/include/linux/sched/topology.h +++ b/include/linux/sched/topology.h @@ -217,6 +217,16 @@ static inline bool cpus_share_cache(int this_cpu, int that_cpu) #endif /* !CONFIG_SMP */ #ifndef arch_scale_cpu_capacity +/** + * arch_scale_cpu_capacity - get the capacity scale factor of a given CPU. + * @cpu: the CPU in question. + * + * Return: the CPU scale factor normalized against SCHED_CAPACITY_SCALE, i.e. + * + * max_perf(cpu) + * ----------------------------- * SCHED_CAPACITY_SCALE + * max(max_perf(c) : c \in CPUs) + */ static __always_inline unsigned long arch_scale_cpu_capacity(int cpu) { -- cgit v1.2.3