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Message-ID: <20240916164722.1838-2-ravi.bangoria@amd.com>
Date: Mon, 16 Sep 2024 16:47:18 +0000
From: Ravi Bangoria <ravi.bangoria@....com>
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<namhyung@...nel.org>, <irogers@...gle.com>
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Subject: [PATCH 1/5] sched/stats: Print domain name in /proc/schedstat
From: K Prateek Nayak <kprateek.nayak@....com>
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 schedstat` require displaying per-domain
information in user friendly manner, display the names of sched domain,
alongside their level in /proc/schedstat if CONFIG_SCHED_DEBUG is enabled.
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 ...
schedstat version has not been updated since this change merely adds
additional information to the domain name field and does not add a new
field altogether.
Signed-off-by: K Prateek Nayak <kprateek.nayak@....com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
---
Documentation/scheduler/sched-stats.rst | 8 ++++++--
kernel/sched/stats.c | 6 +++++-
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/Documentation/scheduler/sched-stats.rst b/Documentation/scheduler/sched-stats.rst
index 7c2b16c4729d..b60a3e7bc108 100644
--- a/Documentation/scheduler/sched-stats.rst
+++ b/Documentation/scheduler/sched-stats.rst
@@ -6,6 +6,8 @@ Version 16 of schedstats changed the order of definitions within
'enum cpu_idle_type', which changed the order of [CPU_MAX_IDLE_TYPES]
columns in show_schedstat(). In particular the position of CPU_IDLE
and __CPU_NOT_IDLE changed places. The size of the array is unchanged.
+With CONFIG_SCHED_DEBUG enabled, the domain field can also print the
+name of the corresponding sched domain.
Version 15 of schedstats dropped counters for some sched_yield:
yld_exp_empty, yld_act_empty and yld_both_empty. Otherwise, it is
@@ -71,9 +73,11 @@ Domain statistics
-----------------
One of these is produced per domain for each cpu described. (Note that if
CONFIG_SMP is not defined, *no* domains are utilized and these lines
-will not appear in the output.)
+will not appear in the output. [:<name>] is an optional extension to the domain
+field that prints the name of the corresponding sched domain. It can appear in
+schedstat version 16 and above, and requires CONFIG_SCHED_DEBUG.)
-domain<N> <cpumask> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
+domain<N>[:<name>] <cpumask> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
The first field is a bit mask indicating what cpus this domain operates over.
diff --git a/kernel/sched/stats.c b/kernel/sched/stats.c
index eb0cdcd4d921..bd4ed737e894 100644
--- a/kernel/sched/stats.c
+++ b/kernel/sched/stats.c
@@ -138,7 +138,11 @@ 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", dcount++);
+#ifdef CONFIG_SCHED_DEBUG
+ seq_printf(seq, ":%s", sd->name);
+#endif
+ seq_printf(seq, " %*pb",
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",
--
2.46.0
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