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sched: use a 2-d bitmap for searching lowest-pri CPU

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The current code use a linear algorithm which causes scaling issues
on larger SMP machines.  This patch replaces that algorithm with a
2-dimensional bitmap to reduce latencies in the wake-up path.

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Gregory Haskins
2008-05-12 21:21:01 +02:00
committed by Ingo Molnar
parent f333fdc909
commit 6e0534f278
5 changed files with 239 additions and 77 deletions
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36
kernel/sched_cpupri.h Normal file
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#ifndef _LINUX_CPUPRI_H
#define _LINUX_CPUPRI_H
#include <linux/sched.h>
#define CPUPRI_NR_PRIORITIES 2+MAX_RT_PRIO
#define CPUPRI_NR_PRI_WORDS CPUPRI_NR_PRIORITIES/BITS_PER_LONG
#define CPUPRI_INVALID -1
#define CPUPRI_IDLE 0
#define CPUPRI_NORMAL 1
/* values 2-101 are RT priorities 0-99 */
struct cpupri_vec {
spinlock_t lock;
int count;
cpumask_t mask;
};
struct cpupri {
struct cpupri_vec pri_to_cpu[CPUPRI_NR_PRIORITIES];
long pri_active[CPUPRI_NR_PRI_WORDS];
int cpu_to_pri[NR_CPUS];
};
#ifdef CONFIG_SMP
int cpupri_find(struct cpupri *cp,
struct task_struct *p, cpumask_t *lowest_mask);
void cpupri_set(struct cpupri *cp, int cpu, int pri);
void cpupri_init(struct cpupri *cp);
#else
#define cpupri_set(cp, cpu, pri) do { } while (0)
#define cpupri_init() do { } while (0)
#endif
#endif /* _LINUX_CPUPRI_H */