[tip: sched/core] sched/stats: Print domain name in /proc/schedstat

[tip-bot2 for K Prateek Nayak]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     011b3a14dc66c40066d08d60a768e14ede7ef351
Gitweb:        https://git.kernel.org/tip/011b3a14dc66c40066d08d60a768e14ede7ef351
Author:        K Prateek Nayak <kprateek.nayak@xxxxxxx>
AuthorDate:    Fri, 20 Dec 2024 06:32:23 
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Fri, 20 Dec 2024 15:31:18 +01:00

sched/stats: Print domain name in /proc/schedstat

Currently, there does not exist a straightforward way to extract the
names of the sched domains and match them to the per-cpu domain entry in
/proc/schedstat other than looking at the debugfs files which are only
visible after enabling "verbose" debug after commit 34320745dfc9
("sched/debug: Put sched/domains files under the verbose flag")

Since tools like `perf sched stats`[1] require displaying per-domain
information in user friendly manner, display the names of sched domain,
alongside their level in /proc/schedstat.

Domain names also makes the /proc/schedstat data unambiguous when some
of the cpus are offline. For example, on a 128 cpus AMD Zen3 machine
where CPU0 and CPU64 are SMT siblings and CPU64 is offline:

Before:
    cpu0 ...
    domain0 ...
    domain1 ...
    cpu1 ...
    domain0 ...
    domain1 ...
    domain2 ...

After:
    cpu0 ...
    domain0 MC ...
    domain1 PKG ...
    cpu1 ...
    domain0 SMT ...
    domain1 MC ...
    domain2 PKG ...

[1] https://lore.kernel.org/lkml/20241122084452.1064968-1-swapnil.sapkal@xxxxxxx/

Signed-off-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxx>
Signed-off-by: Swapnil Sapkal <swapnil.sapkal@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: James Clark <james.clark@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241220063224.17767-6-swapnil.sapkal@xxxxxxx
---
 kernel/sched/stats.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/stats.c b/kernel/sched/stats.c
index 802bd93..5f56396 100644
--- a/kernel/sched/stats.c
+++ b/kernel/sched/stats.c
@@ -138,7 +138,7 @@ static int show_schedstat(struct seq_file *seq, void *v)
 		for_each_domain(cpu, sd) {
 			enum cpu_idle_type itype;
 
-			seq_printf(seq, "domain%d %*pb", dcount++,
+			seq_printf(seq, "domain%d %s %*pb", dcount++, sd->name,
 				   cpumask_pr_args(sched_domain_span(sd)));
 			for (itype = 0; itype < CPU_MAX_IDLE_TYPES; itype++) {
 				seq_printf(seq, " %u %u %u %u %u %u %u %u %u %u %u",