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sched/fair, cpumask: Export for_each_cpu_wrap() 

More users for for_each_cpu_wrap() have appeared. Promote the construct
to generic cpumask interface.

The implementation is slightly modified to reduce arguments.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Lauro Ramos Venancio <lvenanci@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: lwang@redhat.com
Link: http://lkml.kernel.org/r/20170414122005.o35me2h5nowqkxbv@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2017-04-14 14:20:05 +02:00 committed by Ingo Molnar
parent 8c0334697d
commit c743f0a5c5
3 changed files with 53 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
include/linux/cpumask.h
View File

@ -236,6 +236,23 @@ unsigned int cpumask_local_spread(unsigned int i, int node);
(cpu) = cpumask_next_zero((cpu), (mask)), \
(cpu) < nr_cpu_ids;)
extern int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap);
/**
* for_each_cpu_wrap - iterate over every cpu in a mask, starting at a specified location
* @cpu: the (optionally unsigned) integer iterator
* @mask: the cpumask poiter
* @start: the start location
*
* The implementation does not assume any bit in @mask is set (including @start).
*
* After the loop, cpu is >= nr_cpu_ids.
*/
#define for_each_cpu_wrap(cpu, mask, start) \
for ((cpu) = cpumask_next_wrap((start)-1, (mask), (start), false); \
(cpu) < nr_cpumask_bits; \
(cpu) = cpumask_next_wrap((cpu), (mask), (start), true))
/**
* for_each_cpu_and - iterate over every cpu in both masks
* @cpu: the (optionally unsigned) integer iterator

45
kernel/sched/fair.c
View File

@ -5640,43 +5640,6 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu;
}
/*
* Implement a for_each_cpu() variant that starts the scan at a given cpu
* (@start), and wraps around.
*
* This is used to scan for idle CPUs; such that not all CPUs looking for an
* idle CPU find the same CPU. The down-side is that tasks tend to cycle
* through the LLC domain.
*
* Especially tbench is found sensitive to this.
*/
static int cpumask_next_wrap(int n, const struct cpumask *mask, int start, int *wrapped)
{
int next;
again:
next = find_next_bit(cpumask_bits(mask), nr_cpumask_bits, n+1);
if (*wrapped) {
if (next >= start)
return nr_cpumask_bits;
} else {
if (next >= nr_cpumask_bits) {
*wrapped = 1;
n = -1;
goto again;
}
}
return next;
}
#define for_each_cpu_wrap(cpu, mask, start, wrap) \
for ((wrap) = 0, (cpu) = (start)-1; \
(cpu) = cpumask_next_wrap((cpu), (mask), (start), &(wrap)), \
(cpu) < nr_cpumask_bits; )
#ifdef CONFIG_SCHED_SMT
static inline void set_idle_cores(int cpu, int val)
@ -5736,7 +5699,7 @@ unlock:
static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int target)
{
struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
int core, cpu, wrap;
int core, cpu;
if (!static_branch_likely(&sched_smt_present))
return -1;
@ -5746,7 +5709,7 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
cpumask_and(cpus, sched_domain_span(sd), &p->cpus_allowed);
for_each_cpu_wrap(core, cpus, target, wrap) {
for_each_cpu_wrap(core, cpus, target) {
bool idle = true;
for_each_cpu(cpu, cpu_smt_mask(core)) {
@ -5812,7 +5775,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
u64 avg_cost, avg_idle = this_rq()->avg_idle;
u64 time, cost;
s64 delta;
int cpu, wrap;
int cpu;
this_sd = rcu_dereference(*this_cpu_ptr(&sd_llc));
if (!this_sd)
@ -5829,7 +5792,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
time = local_clock();
for_each_cpu_wrap(cpu, sched_domain_span(sd), target, wrap) {
for_each_cpu_wrap(cpu, sched_domain_span(sd), target) {
if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
continue;
if (idle_cpu(cpu))

32
lib/cpumask.c
View File

@ -43,6 +43,38 @@ int cpumask_any_but(const struct cpumask *mask, unsigned int cpu)
}
EXPORT_SYMBOL(cpumask_any_but);
/**
* cpumask_next_wrap - helper to implement for_each_cpu_wrap
* @n: the cpu prior to the place to search
* @mask: the cpumask pointer
* @start: the start point of the iteration
* @wrap: assume @n crossing @start terminates the iteration
*
* Returns >= nr_cpu_ids on completion
*
* Note: the @wrap argument is required for the start condition when
* we cannot assume @start is set in @mask.
*/
int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
{
int next;
again:
next = cpumask_next(n, mask);
if (wrap && n < start && next >= start) {
return nr_cpumask_bits;
} else if (next >= nr_cpumask_bits) {
wrap = true;
n = -1;
goto again;
}
return next;
}
EXPORT_SYMBOL(cpumask_next_wrap);
/* These are not inline because of header tangles. */
#ifdef CONFIG_CPUMASK_OFFSTACK
/**