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Subject[tip:sched/core] sched: Change rq->nr_running to unsigned int
Commit-ID:  c82513e513556a04f81aa511cd890acd23349c48
Gitweb: http://git.kernel.org/tip/c82513e513556a04f81aa511cd890acd23349c48
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Thu, 26 Apr 2012 13:12:27 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 9 May 2012 15:00:49 +0200

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: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-y3tvyszjdmbibade5bw8zl81@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/debug.c | 2 +-
kernel/sched/fair.c | 8 ++++----
kernel/sched/sched.h | 6 +++---
3 files changed, 8 insertions(+), 8 deletions(-)
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 09acaa1..31e4f61 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -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
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e955364..678966c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4447,10 +4447,10 @@ redo:
* correctly treated as an imbalance.
*/
env.flags |= LBF_ALL_PINNED;
- 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.load_move = imbalance;
+ env.src_cpu = busiest->cpu;
+ env.src_rq = busiest;
+ env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);

more_balance:
local_irq_save(flags);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index fb3acba..7282e7b 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -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;

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