From: Nicolas Hillegeer <aktau@google.com>
Date: Thu, 12 Dec 2024 16:49:03 +0000 (-0800)
Subject: runtime: print pp.schedtick in scheddetail even when !detailed
X-Git-Tag: go1.25rc1~1001
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=5295722238446f09197adb2c5a8ba27fe1076973;p=gostls13.git

runtime: print pp.schedtick in scheddetail even when !detailed

Provides, on one line, an approximation of P scheduling throughput: how
many times execute() was called for a given P. Said another way: how
many RUNNABLE to RUNNING transitions have happened for this P.

This allows discerning whether a P actually did anything, and how it
compares to other periods of a processes operation.

This should be useful to analyze (kernel) scheduler hiccups.

Investigators will want to subtract the tick values from subsequent
schedtrace lines to get a rate of schedulings. I've opted to add a space
around the first and last element as well to make it more uniform to do
the proposed subtracting with tools like AWK.

Change-Id: I69d6dae1509ad285d43799f38bcaa3aa0fb2352e
Reviewed-on: https://go-review.googlesource.com/c/go/+/635636
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Nicolas Hillegeer <aktau@google.com>
---

diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index c9d04edd07..98e135ff2a 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -6404,18 +6404,28 @@ func schedtrace(detailed bool) {
 			print(" runqsize=", t-h, " gfreecnt=", pp.gFree.n, " timerslen=", len(pp.timers.heap), "\n")
 		} else {
 			// In non-detailed mode format lengths of per-P run queues as:
-			// [len1 len2 len3 len4]
+			// [ len1 len2 len3 len4 ]
 			print(" ")
 			if i == 0 {
-				print("[")
+				print("[ ")
 			}
 			print(t - h)
 			if i == len(allp)-1 {
-				print("]\n")
+				print(" ]")
 			}
 		}
 	}
 
+	if !detailed {
+		// Format per-P schedticks as: schedticks=[ tick1 tick2 tick3 tick4 ].
+		print(" schedticks=[ ")
+		for _, pp := range allp {
+			print(pp.schedtick)
+			print(" ")
+		}
+		print("]\n")
+	}
+
 	if !detailed {
 		unlock(&sched.lock)
 		return