[v3] sched: print information about scheduling granularity

Commit Message

Sergey Dyasli April 22, 2020, 9:30 a.m. UTC

Currently it might be not obvious which scheduling mode (e.g. core-
scheduling) is being used by the scheduler. Alleviate this by printing
additional information about the selected granularity per-cpupool.

Note: per-cpupool granularity selection is not implemented yet. Every
      cpupool gets its granularity from the single global value.

Take this opportunity to introduce struct sched_gran_name array and
refactor sched_select_granularity().

Signed-off-by: Sergey Dyasli <[e-mail]>
---
v3:
- use const char*
- use sched_gran_name array instead of switch
- updated commit message

v2:
- print information on a separate line
- use per-cpupool granularity
- updated commit message

CC: Juergen Gross <[e-mail]>
CC: Dario Faggioli <[e-mail]>
CC: George Dunlap <[e-mail]>
CC: Jan Beulich <[e-mail]>
---
 xen/common/sched/cpupool.c | 51 +++++++++++++++++++++++++++++++-------
 1 file changed, 42 insertions(+), 9 deletions(-)

Comments

Jan Beulich April 22, 2020, 10:50 a.m. UTC | #1

On 22.04.2020 11:30, Sergey Dyasli wrote:
> --- a/xen/common/sched/cpupool.c
> +++ b/xen/common/sched/cpupool.c
> @@ -40,19 +40,50 @@ 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;
>  
> +struct sched_gran_name {
> +    enum sched_gran mode;
> +    const char *name;
> +};
> +
> +static const struct sched_gran_name sg_name[] = {
> +    {SCHED_GRAN_cpu, "cpu"},
> +    {SCHED_GRAN_core, "core"},
> +    {SCHED_GRAN_socket, "socket"},
> +};

Personally I think that in cases like this one it is more
(space) efficient to use char[8] or so for the second
struct member.

Jan

Dario Faggioli May 4, 2020, 2:46 p.m. UTC | #2

On Wed, 2020-04-22 at 12:50 +0200, Jan Beulich wrote:
> On 22.04.2020 11:30, Sergey Dyasli wrote:
> > +struct sched_gran_name {
> > +    enum sched_gran mode;
> > +    const char *name;
> > +};
> > +
> > +static const struct sched_gran_name sg_name[] = {
> > +    {SCHED_GRAN_cpu, "cpu"},
> > +    {SCHED_GRAN_core, "core"},
> > +    {SCHED_GRAN_socket, "socket"},
> > +};
> 
> Personally I think that in cases like this one it is more
> (space) efficient to use char[8] or so for the second
> struct member.
>
Yeah, I think that is actually better.

Sergey, can you do it like this?

Thanks and Regards

Patch

diff --git a/xen/common/sched/cpupool.c b/xen/common/sched/cpupool.c
index d40345b585..b60799a558 100644
--- a/xen/common/sched/cpupool.c
+++ b/xen/common/sched/cpupool.c
@@ -40,19 +40,50 @@  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;
 
+struct sched_gran_name {
+    enum sched_gran mode;
+    const char *name;
+};
+
+static const struct sched_gran_name sg_name[] = {
+    {SCHED_GRAN_cpu, "cpu"},
+    {SCHED_GRAN_core, "core"},
+    {SCHED_GRAN_socket, "socket"},
+};
+
+static void sched_gran_print(enum sched_gran mode, unsigned int gran)
+{
+    const char *name = "";
+    unsigned int i;
+
+    for ( i = 0; i < ARRAY_SIZE(sg_name); i++ )
+    {
+        if ( mode == sg_name[i].mode )
+        {
+            name = sg_name[i].name;
+            break;
+        }
+    }
+
+    printk("Scheduling granularity: %s, %u CPU%s per sched-resource\n",
+           name, gran, gran == 1 ? "" : "s");
+}
+
 #ifdef CONFIG_HAS_SCHED_GRANULARITY
 static int __init sched_select_granularity(const char *str)
 {
-    if ( strcmp("cpu", str) == 0 )
-        opt_sched_granularity = SCHED_GRAN_cpu;
-    else if ( strcmp("core", str) == 0 )
-        opt_sched_granularity = SCHED_GRAN_core;
-    else if ( strcmp("socket", str) == 0 )
-        opt_sched_granularity = SCHED_GRAN_socket;
-    else
-        return -EINVAL;
+    unsigned int i;
 
-    return 0;
+    for ( i = 0; i < ARRAY_SIZE(sg_name); i++ )
+    {
+        if ( strcmp(sg_name[i].name, str) == 0 )
+        {
+            opt_sched_granularity = sg_name[i].mode;
+            return 0;
+        }
+    }
+
+    return -EINVAL;
 }
 custom_param("sched-gran", sched_select_granularity);
 #endif
@@ -115,6 +146,7 @@  static void __init cpupool_gran_init(void)
         warning_add(fallback);
 
     sched_granularity = gran;
+    sched_gran_print(opt_sched_granularity, sched_granularity);
 }
 
 unsigned int cpupool_get_granularity(const struct cpupool *c)
@@ -911,6 +943,7 @@  void dump_runq(unsigned char key)
     {
         printk("Cpupool %d:\n", (*c)->cpupool_id);
         printk("Cpus: %*pbl\n", CPUMASK_PR((*c)->cpu_valid));
+        sched_gran_print((*c)->gran, cpupool_get_granularity(*c));
         schedule_dump(*c);
     }