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Subject[29/98] sched: Fix missing sched tunable recalculation on cpu add/remove
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>

commit 0bcdcf28c979869f44e05121b96ff2cfb05bd8e6 upstream.

Based on Peter Zijlstras patch suggestion this enables recalculation of
the scheduler tunables in response of a change in the number of cpus. It
also adds a max of eight cpus that are considered in that scaling.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1259579808-11357-2-git-send-email-ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
kernel/sched.c | 29 ++++++++++++++++-------------
kernel/sched_fair.c | 16 ++++++++++++++++
2 files changed, 32 insertions(+), 13 deletions(-)

--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -816,6 +816,7 @@ const_debug unsigned int sysctl_sched_nr
* default: 0.25ms
*/
unsigned int sysctl_sched_shares_ratelimit = 250000;
+unsigned int normalized_sysctl_sched_shares_ratelimit = 250000;

/*
* Inject some fuzzyness into changing the per-cpu group shares
@@ -1812,6 +1813,7 @@ static void cfs_rq_set_shares(struct cfs
#endif

static void calc_load_account_active(struct rq *this_rq);
+static void update_sysctl(void);

#include "sched_stats.h"
#include "sched_idletask.c"
@@ -7018,22 +7020,23 @@ cpumask_var_t nohz_cpu_mask;
*
* This idea comes from the SD scheduler of Con Kolivas:
*/
-static inline void sched_init_granularity(void)
+static void update_sysctl(void)
{
- unsigned int factor = 1 + ilog2(num_online_cpus());
- const unsigned long limit = 200000000;
-
- sysctl_sched_min_granularity *= factor;
- if (sysctl_sched_min_granularity > limit)
- sysctl_sched_min_granularity = limit;
-
- sysctl_sched_latency *= factor;
- if (sysctl_sched_latency > limit)
- sysctl_sched_latency = limit;
+ unsigned int cpus = min(num_online_cpus(), 8U);
+ unsigned int factor = 1 + ilog2(cpus);

- sysctl_sched_wakeup_granularity *= factor;
+#define SET_SYSCTL(name) \
+ (sysctl_##name = (factor) * normalized_sysctl_##name)
+ SET_SYSCTL(sched_min_granularity);
+ SET_SYSCTL(sched_latency);
+ SET_SYSCTL(sched_wakeup_granularity);
+ SET_SYSCTL(sched_shares_ratelimit);
+#undef SET_SYSCTL
+}

- sysctl_sched_shares_ratelimit *= factor;
+static inline void sched_init_granularity(void)
+{
+ update_sysctl();
}

#ifdef CONFIG_SMP
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -35,12 +35,14 @@
* run vmstat and monitor the context-switches (cs) field)
*/
unsigned int sysctl_sched_latency = 5000000ULL;
+unsigned int normalized_sysctl_sched_latency = 5000000ULL;

/*
* Minimal preemption granularity for CPU-bound tasks:
* (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
*/
unsigned int sysctl_sched_min_granularity = 1000000ULL;
+unsigned int normalized_sysctl_sched_min_granularity = 1000000ULL;

/*
* is kept at sysctl_sched_latency / sysctl_sched_min_granularity
@@ -70,6 +72,7 @@ unsigned int __read_mostly sysctl_sched_
* have immediate wakeup/sleep latencies.
*/
unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
+unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;

const_debug unsigned int sysctl_sched_migration_cost = 500000UL;

@@ -1880,6 +1883,17 @@ move_one_task_fair(struct rq *this_rq, i

return 0;
}
+
+static void rq_online_fair(struct rq *rq)
+{
+ update_sysctl();
+}
+
+static void rq_offline_fair(struct rq *rq)
+{
+ update_sysctl();
+}
+
#endif /* CONFIG_SMP */

/*
@@ -2027,6 +2041,8 @@ static const struct sched_class fair_sch

.load_balance = load_balance_fair,
.move_one_task = move_one_task_fair,
+ .rq_online = rq_online_fair,
+ .rq_offline = rq_offline_fair,
#endif

.set_curr_task = set_curr_task_fair,



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