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

JIRA: https://issues.redhat.com/browse/RHEL-24185

commit 011b3a1
Author: K Prateek Nayak <kprateek.nayak@amd.com>
Date:   Fri Dec 20 06:32:23 2024 +0000

    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 3432074
    ("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@amd.com/

    Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
    Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
    Signed-off-by: Swapnil Sapkal <swapnil.sapkal@amd.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Tested-by: James Clark <james.clark@linaro.org>
    Link: https://lore.kernel.org/r/20241220063224.17767-6-swapnil.sapkal@amd.com

Signed-off-by: Phil Auld <pauld@redhat.com>

Author: auldp

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",