sched: Fix missing sched tunable recalculation on cpu add/remove
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>
diff --git a/kernel/sched.c b/kernel/sched.c
index 3878f50..b54ecf8 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -814,6 +814,7 @@
* 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
@@ -1814,6 +1815,7 @@
#endif
static void calc_load_account_active(struct rq *this_rq);
+static void update_sysctl(void);
static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
{
@@ -7028,22 +7030,23 @@
*
* This idea comes from the SD scheduler of Con Kolivas:
*/
+static void update_sysctl(void)
+{
+ unsigned int cpus = min(num_online_cpus(), 8U);
+ unsigned int factor = 1 + ilog2(cpus);
+
+#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
+}
+
static inline void sched_init_granularity(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;
-
- sysctl_sched_wakeup_granularity *= factor;
-
- sysctl_sched_shares_ratelimit *= factor;
+ update_sysctl();
}
#ifdef CONFIG_SMP