[PATCH 12/14] sched/topology,debug: Add sched_group_capacity debugging

From: Peter Zijlstra
Date: Fri Apr 28 2017 - 09:33:51 EST


Add sgc::id to easier spot domain construction issues.

Take the opportunity to slightly rework the group printing, because
adding more "(id: %d)" strings makes the entire thing very hard to
read. Also the individual groups are very hard to separate, so add
explicit visual grouping, which allows replacing all the "(%s: %d)"
format things with shorter "%s=%d" variants.

Then fix up some inconsistencies in surrounding prints for domains.

The end result looks like:

[] CPU0 attaching sched-domain(s):
[] domain-0: span=0,4 level=DIE
[] groups: 0:{ span=0 }, 4:{ span=4 }
[] domain-1: span=0-1,3-5,7 level=NUMA
[] groups: 0:{ span=0,4 mask=0,4 cap=2048 }, 1:{ span=1,5 mask=1,5 cap=2048 }, 3:{ span=3,7 mask=3,7 cap=2048 }
[] domain-2: span=0-7 level=NUMA
[] groups: 0:{ span=0-1,3-5,7 mask=0,4 cap=6144 }, 2:{ span=1-3,5-7 mask=2,6 cap=6144 }

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
kernel/sched/sched.h | 4 ++++
kernel/sched/topology.c | 25 +++++++++++++++----------
2 files changed, 19 insertions(+), 10 deletions(-)

--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1023,6 +1023,10 @@ struct sched_group_capacity {
unsigned long next_update;
int imbalance; /* XXX unrelated to capacity but shared group state */

+#ifdef CONFIG_SCHED_DEBUG
+ int id;
+#endif
+
unsigned long cpumask[0]; /* iteration mask */
};

--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -35,7 +35,7 @@ static int sched_domain_debug_one(struct

cpumask_clear(groupmask);

- printk(KERN_DEBUG "%*s domain %d: ", level, "", level);
+ printk(KERN_DEBUG "%*s domain-%d: ", level, "", level);

if (!(sd->flags & SD_LOAD_BALANCE)) {
printk("does not load-balance\n");
@@ -45,7 +45,7 @@ static int sched_domain_debug_one(struct
return -1;
}

- printk(KERN_CONT "span %*pbl level %s\n",
+ printk(KERN_CONT "span=%*pbl level=%s\n",
cpumask_pr_args(sched_domain_span(sd)), sd->name);

if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) {
@@ -80,18 +80,17 @@ static int sched_domain_debug_one(struct

cpumask_or(groupmask, groupmask, sched_group_cpus(group));

- printk(KERN_CONT " %*pbl",
- cpumask_pr_args(sched_group_cpus(group)));
+ printk(KERN_CONT " %d:{ span=%*pbl",
+ group->sgc->id,
+ cpumask_pr_args(sched_group_cpus(group)));

if ((sd->flags & SD_OVERLAP) && !cpumask_full(sched_group_mask(group))) {
- printk(KERN_CONT " (mask: %*pbl)",
+ printk(KERN_CONT " mask=%*pbl",
cpumask_pr_args(sched_group_mask(group)));
}

- if (group->sgc->capacity != SCHED_CAPACITY_SCALE) {
- printk(KERN_CONT " (cpu_capacity: %lu)",
- group->sgc->capacity);
- }
+ if (group->sgc->capacity != SCHED_CAPACITY_SCALE)
+ printk(KERN_CONT " cap=%lu", group->sgc->capacity);

if (group == sd->groups && sd->child &&
!cpumask_equal(sched_domain_span(sd->child),
@@ -99,6 +98,8 @@ static int sched_domain_debug_one(struct
printk(KERN_ERR "ERROR: domain->groups does not match domain->child\n");
}

+ printk(KERN_CONT " }");
+
group = group->next;

if (group != sd->groups)
@@ -129,7 +130,7 @@ static void sched_domain_debug(struct sc
return;
}

- printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu);
+ printk(KERN_DEBUG "CPU%d attaching sched-domain(s):\n", cpu);

for (;;) {
if (sched_domain_debug_one(sd, cpu, level, sched_domains_tmpmask))
@@ -1356,6 +1357,10 @@ static int __sdt_alloc(const struct cpum
if (!sgc)
return -ENOMEM;

+#ifdef CONFIG_SCHED_DEBUG
+ sgc->id = j;
+#endif
+
*per_cpu_ptr(sdd->sgc, j) = sgc;
}
}