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Commit c82513e5 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Change rq->nr_running to unsigned int 



Since there's a PID space limit of 30bits (see
futex.h:FUTEX_TID_MASK) and allocating that many tasks (assuming a
lower bound of 2 pages per task) would still take 8T of memory it
seems reasonable to say that unsigned int is sufficient for
rq->nr_running.

When we do get anywhere near that amount of tasks I suspect other
things would go funny, load-balancer load computations would really
need to be hoisted to 128bit etc.

So save a few bytes and convert rq->nr_running and friends to
unsigned int.

Suggested-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-y3tvyszjdmbibade5bw8zl81@git.kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ad7687dd

kernel/sched/debug.c

+1 −1
Original line number Diff line number Diff line
@@ -202,7 +202,7 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) 
			SPLIT_NS(spread0));

	SEQ_printf(m, "  .%-30s: %d\n", "nr_spread_over",

			cfs_rq->nr_spread_over);

	SEQ_printf(m, "  .%-30s: %ld\n", "nr_running", cfs_rq->nr_running);

	SEQ_printf(m, "  .%-30s: %d\n", "nr_running", cfs_rq->nr_running);

	SEQ_printf(m, "  .%-30s: %ld\n", "load", cfs_rq->load.weight);

#ifdef CONFIG_FAIR_GROUP_SCHED

#ifdef CONFIG_SMP

kernel/sched/fair.c

+4 −4
Original line number Diff line number Diff line
@@ -4450,7 +4450,7 @@ redo: 
		env.load_move = imbalance;

		env.src_cpu   = busiest->cpu;

		env.src_rq    = busiest;

		env.loop_max	= min_t(unsigned long, sysctl_sched_nr_migrate, busiest->nr_running);

		env.loop_max  = min(sysctl_sched_nr_migrate, busiest->nr_running);



more_balance:

		local_irq_save(flags);

kernel/sched/sched.h

+3 −3
Original line number Diff line number Diff line
@@ -201,7 +201,7 @@ struct cfs_bandwidth { }; 
/* CFS-related fields in a runqueue */

struct cfs_rq {

	struct load_weight load;

	unsigned long nr_running, h_nr_running;

	unsigned int nr_running, h_nr_running;



	u64 exec_clock;

	u64 min_vruntime;
@@ -279,7 +279,7 @@ static inline int rt_bandwidth_enabled(void) 
/* Real-Time classes' related field in a runqueue: */

struct rt_rq {

	struct rt_prio_array active;

	unsigned long rt_nr_running;

	unsigned int rt_nr_running;

#if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED

	struct {

		int curr; /* highest queued rt task prio */
@@ -353,7 +353,7 @@ struct rq { 
	 * nr_running and cpu_load should be in the same cacheline because

	 * remote CPUs use both these fields when doing load calculation.

	 */

	unsigned long nr_running;

	unsigned int nr_running;

	#define CPU_LOAD_IDX_MAX 5

	unsigned long cpu_load[CPU_LOAD_IDX_MAX];

	unsigned long last_load_update_tick;