sched: Make tunable scaling style configurable

As scaling now takes place on all kind of cpu add/remove events a user
that configures values via proc should be able to configure if his set
values are still rescaled or kept whatever happens.

As the comments state that log2 was just a second guess that worked the
interface is not just designed for on/off, but to choose a scaling type.
Currently this allows none, log and linear, but more important it allwos
us to keep the interface even if someone has an even better idea how to
scale the values.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1259579808-11357-3-git-send-email-ehrhardt@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4b1ebd3280c6d1e1593eb939a55c9ef34749cb60..ee9f200d12d301c2950e3e95c0c97321cfe32e9d 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1902,13 +1902,22 @@ extern unsigned int sysctl_sched_wakeup_granularity;
 extern unsigned int sysctl_sched_shares_ratelimit;
 extern unsigned int sysctl_sched_shares_thresh;
 extern unsigned int sysctl_sched_child_runs_first;
+
+enum sched_tunable_scaling {
+       SCHED_TUNABLESCALING_NONE,
+       SCHED_TUNABLESCALING_LOG,
+       SCHED_TUNABLESCALING_LINEAR,
+       SCHED_TUNABLESCALING_END,
+};
+extern enum sched_tunable_scaling sysctl_sched_tunable_scaling;
+
 #ifdef CONFIG_SCHED_DEBUG
 extern unsigned int sysctl_sched_migration_cost;
 extern unsigned int sysctl_sched_nr_migrate;
 extern unsigned int sysctl_sched_time_avg;
 extern unsigned int sysctl_timer_migration;
 
-int sched_nr_latency_handler(struct ctl_table *table, int write,
+int sched_proc_update_handler(struct ctl_table *table, int write,
                void __user *buffer, size_t *length,
                loff_t *ppos);
 #endif

diff --git a/kernel/sched.c b/kernel/sched.c
index b54ecf84b6be94096715b0f5ea64608c117694bd..116efed962c6e4bb747b17a955915758f636040c 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7033,7 +7033,20 @@ cpumask_var_t nohz_cpu_mask;
 static void update_sysctl(void)
 {
        unsigned int cpus = min(num_online_cpus(), 8U);
-       unsigned int factor = 1 + ilog2(cpus);
+       unsigned int factor;
+
+       switch (sysctl_sched_tunable_scaling) {
+       case SCHED_TUNABLESCALING_NONE:
+               factor = 1;
+               break;
+       case SCHED_TUNABLESCALING_LINEAR:
+               factor = cpus;
+               break;
+       case SCHED_TUNABLESCALING_LOG:
+       default:
+               factor = 1 + ilog2(cpus);
+               break;
+       }
 
 #define SET_SYSCTL(name) \
        (sysctl_##name = (factor) * normalized_sysctl_##name)

diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c
index 5fda66615feef268487f587226556340133c71bc..0fc5287fe80f21d16937397523d2ba2141b2eb57 100644 (file)
--- a/kernel/sched_debug.c
+++ b/kernel/sched_debug.c
@@ -309,6 +309,12 @@ static void print_cpu(struct seq_file *m, int cpu)
        print_rq(m, rq, cpu);
 }
 
+static const char *sched_tunable_scaling_names[] = {
+       "none",
+       "logaritmic",
+       "linear"
+};
+
 static int sched_debug_show(struct seq_file *m, void *v)
 {
        u64 now = ktime_to_ns(ktime_get());
@@ -334,6 +340,10 @@ static int sched_debug_show(struct seq_file *m, void *v)
 #undef PN
 #undef P
 
+       SEQ_printf(m, "  .%-40s: %d (%s)\n", "sysctl_sched_tunable_scaling",
+               sysctl_sched_tunable_scaling,
+               sched_tunable_scaling_names[sysctl_sched_tunable_scaling]);
+
        for_each_online_cpu(cpu)
                print_cpu(m, cpu);
 

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 71b3458245e593f8b4421197b9ad43977866966d..455106d318a8ae5c87e7a56c19c8e8c05ced83cd 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -21,6 +21,7 @@
  */
 
 #include <linux/latencytop.h>
+#include <linux/sched.h>
 
 /*
  * Targeted preemption latency for CPU-bound tasks:
@@ -37,6 +38,18 @@
 unsigned int sysctl_sched_latency = 5000000ULL;
 unsigned int normalized_sysctl_sched_latency = 5000000ULL;
 
+/*
+ * The initial- and re-scaling of tunables is configurable
+ * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
+ *
+ * Options are:
+ * SCHED_TUNABLESCALING_NONE - unscaled, always *1
+ * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
+ * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
+ */
+enum sched_tunable_scaling sysctl_sched_tunable_scaling
+       = SCHED_TUNABLESCALING_LOG;
+
 /*
  * Minimal preemption granularity for CPU-bound tasks:
  * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index e5cc53514caac527e0992b7237f759caa64cd2f1..d10406e5fdfe988ba6f5ea34bc13d2ab85f43950 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -251,6 +251,8 @@ static int min_sched_granularity_ns = 100000;               /* 100 usecs */
 static int max_sched_granularity_ns = NSEC_PER_SEC;    /* 1 second */
 static int min_wakeup_granularity_ns;                  /* 0 usecs */
 static int max_wakeup_granularity_ns = NSEC_PER_SEC;   /* 1 second */
+static int min_sched_tunable_scaling = SCHED_TUNABLESCALING_NONE;
+static int max_sched_tunable_scaling = SCHED_TUNABLESCALING_END-1;
 #endif
 
 static struct ctl_table kern_table[] = {
@@ -304,6 +306,18 @@ static struct ctl_table kern_table[] = {
                .mode           = 0644,
                .proc_handler   = &proc_dointvec,
        },
+       {
+               .ctl_name       = CTL_UNNUMBERED,
+               .procname       = "sched_tunable_scaling",
+               .data           = &sysctl_sched_tunable_scaling,
+               .maxlen         = sizeof(enum sched_tunable_scaling),
+               .mode           = 0644,
+               .proc_handler   = &proc_dointvec_minmax,
+               .strategy       = &sysctl_intvec,
+               .extra1         = &min_sched_tunable_scaling,
+               .extra2         = &max_sched_tunable_scaling,
+       },
+
        {
                .ctl_name       = CTL_UNNUMBERED,
                .procname       = "sched_shares_thresh",