[PATCH v6 06/17] sched/debug: Output SD flag names rather than their values

Valentin Schneider
2020-08-17T11:32:23Z

Decoding the output of /proc/sys/kernel/sched_domain/cpu*/domain*/flags has
always been somewhat annoying, as one needs to go fetch the bit -> name
mapping from the source code itself. This encoding can be saved in a script
somewhere, but that isn't safe from flags being added, removed or even
shuffled around.

What matters for debugging purposes is to get *which* flags are set in a
given domain, their associated value is pretty much meaningless.

Make the sd flags debug file output flag names.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
---
kernel/sched/debug.c | 56 +++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 36c54265bb2b..0655524700d2 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -245,6 +245,60 @@ set_table_entry(struct ctl_table *entry,
entry->proc_handler = proc_handler;
}

+static int sd_ctl_doflags(struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ unsigned long flags = *(unsigned long *)table->data;
+ size_t data_size = 0;
+ size_t len = 0;
+ char *tmp;
+ int idx;
+
+ if (write)
+ return 0;
+
+ for_each_set_bit(idx, &flags, __SD_FLAG_CNT) {
+ char *name = sd_flag_debug[idx].name;
+
+ /* Name plus whitespace */
+ data_size += strlen(name) + 1;
+ }
+
+ if (*ppos > data_size) {
+ *lenp = 0;
+ return 0;
+ }
+
+ tmp = kcalloc(data_size + 1, sizeof(*tmp), GFP_KERNEL);
+ if (!tmp)
+ return -ENOMEM;
+
+ for_each_set_bit(idx, &flags, __SD_FLAG_CNT) {
+ char *name = sd_flag_debug[idx].name;
+
+ len += snprintf(tmp + len, strlen(name) + 2, "%s ", name);
+ }
+
+ tmp += *ppos;
+ len -= *ppos;
+
+ if (len > *lenp)
+ len = *lenp;
+ if (len)
+ memcpy(buffer, tmp, len);
+ if (len < *lenp) {
+ ((char *)buffer)[len] = '\n';
+ len++;
+ }
+
+ *lenp = len;
+ *ppos += len;
+
+ kfree(tmp);
+
+ return 0;
+}
+
static struct ctl_table *
sd_alloc_ctl_domain_table(struct sched_domain *sd)
{
@@ -258,7 +312,7 @@ sd_alloc_ctl_domain_table(struct sched_domain *sd)
set_table_entry(&table[2], "busy_factor", &sd->busy_factor, sizeof(int), 0644, proc_dointvec_minmax);
set_table_entry(&table[3], "imbalance_pct", &sd->imbalance_pct, sizeof(int), 0644, proc_dointvec_minmax);
set_table_entry(&table[4], "cache_nice_tries", &sd->cache_nice_tries, sizeof(int), 0644, proc_dointvec_minmax);
- set_table_entry(&table[5], "flags", &sd->flags, sizeof(int), 0444, proc_dointvec_minmax);
+ set_table_entry(&table[5], "flags", &sd->flags, sizeof(int), 0444, sd_ctl_doflags);
set_table_entry(&table[6], "max_newidle_lb_cost", &sd->max_newidle_lb_cost, sizeof(long), 0644, proc_doulongvec_minmax);
set_table_entry(&table[7], "name", sd->name, CORENAME_MAX_SIZE, 0444, proc_dostring);
/* &table[8] is terminator */
--
2.27.0