[PATCH] sched: print information about scheduler granularity

[Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>]

Currently it might be not obvious which scheduling mode is being used
by the scheduler. Alleviate this by printing additional information
about the selected granularity. Messages now look like these:

1. boot
(XEN) [00089808f0ea7496] Using scheduler: SMP Credit Scheduler (credit) in 
core-scheduling mode

2. xl debug-keys r
(XEN) [   45.914314] Scheduler: SMP Credit Scheduler (credit) in 2-way 
core-scheduling mode

Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
---
CC: Juergen Gross <jgross@xxxxxxxx>
CC: Dario Faggioli <dfaggioli@xxxxxxxx>
CC: George Dunlap <george.dunlap@xxxxxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/common/sched/core.c    | 10 ++++++++--
 xen/common/sched/cpupool.c | 30 +++++++++++++++++++++++++++++-
 xen/common/sched/private.h |  2 ++
 3 files changed, 39 insertions(+), 3 deletions(-)

diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index d4a6489929..b1b09a159b 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -2883,6 +2883,7 @@ void scheduler_enable(void)
 void __init scheduler_init(void)
 {
     struct domain *idle_domain;
+    char sched_gran[20];
     int i;
 
     scheduler_enable();
@@ -2937,7 +2938,9 @@ void __init scheduler_init(void)
         BUG();
     register_cpu_notifier(&cpu_schedule_nfb);
 
-    printk("Using scheduler: %s (%s)\n", ops.name, ops.opt_name);
+    printk("Using scheduler: %s (%s) in %s-scheduling mode\n",
+           ops.name, ops.opt_name,
+           sched_gran_str(sched_gran, sizeof(sched_gran)));
     if ( sched_init(&ops) )
         panic("scheduler returned error on init\n");
 
@@ -3267,6 +3270,7 @@ void schedule_dump(struct cpupool *c)
     unsigned int      i, j;
     struct scheduler *sched;
     cpumask_t        *cpus;
+    char              sched_gran[20];
 
     /* Locking, if necessary, must be handled withing each scheduler */
 
@@ -3276,7 +3280,9 @@ void schedule_dump(struct cpupool *c)
     {
         sched = c->sched;
         cpus = c->res_valid;
-        printk("Scheduler: %s (%s)\n", sched->name, sched->opt_name);
+        printk("Scheduler: %s (%s) in %s-scheduling mode\n",
+               sched->name, sched->opt_name,
+               sched_gran_str(sched_gran, sizeof(sched_gran)));
         sched_dump_settings(sched);
     }
     else
diff --git a/xen/common/sched/cpupool.c b/xen/common/sched/cpupool.c
index d40345b585..a37b97f4c2 100644
--- a/xen/common/sched/cpupool.c
+++ b/xen/common/sched/cpupool.c
@@ -38,7 +38,35 @@ static cpumask_t cpupool_locked_cpus;
 static DEFINE_SPINLOCK(cpupool_lock);
 
 static enum sched_gran __read_mostly opt_sched_granularity = SCHED_GRAN_cpu;
-static unsigned int __read_mostly sched_granularity = 1;
+static unsigned int __read_mostly sched_granularity;
+
+char *sched_gran_str(char *str, size_t size)
+{
+    char *mode = "";
+
+    switch ( opt_sched_granularity )
+    {
+    case SCHED_GRAN_cpu:
+        mode = "cpu";
+        break;
+    case SCHED_GRAN_core:
+        mode = "core";
+        break;
+    case SCHED_GRAN_socket:
+        mode = "socket";
+        break;
+    default:
+        ASSERT_UNREACHABLE();
+        break;
+    }
+
+    if ( sched_granularity )
+        snprintf(str, size, "%u-way %s", sched_granularity, mode);
+    else
+        snprintf(str, size, "%s", mode);
+
+    return str;
+}
 
 #ifdef CONFIG_HAS_SCHED_GRANULARITY
 static int __init sched_select_granularity(const char *str)
diff --git a/xen/common/sched/private.h b/xen/common/sched/private.h
index 367811a12f..fd49f545cb 100644
--- a/xen/common/sched/private.h
+++ b/xen/common/sched/private.h
@@ -30,6 +30,8 @@ enum sched_gran {
     SCHED_GRAN_socket
 };
 
+char *sched_gran_str(char *str, size_t size);
+
 /*
  * In order to allow a scheduler to remap the lock->cpu mapping,
  * we have a per-cpu pointer, along with a pre-allocated set of
-- 
2.17.1