felixge

Investigating goroutine state transition

Exported on 9/17/2025 at 11:26:10 GMT+2 from Cursor (1.6.26)

---

User

Does this systemstack call lead to a call that might transition a goroutine that is blocked on networking to runnable state? Follow the functions inside of it and see if they call into the scheduler/netpoll thing to make that happen.

felixge

package main

import (
	"log"
	"os"
	"runtime/trace"
	"time"
)

func main() {

felixge

From 08b6b8208c07c3f764da8a8fbbc01d0b1573748a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Felix=20Geisend=C3=B6rfer?=
 <felix.geisendoerfer@datadoghq.com>
Date: Fri, 10 Mar 2023 11:04:19 +0100
Subject: [PATCH] runtime: use sched.bp for unwinding trace events with frame
 pointers

Depends on CL 472195.

Change-Id: Ibe91debf04569d18ccb2eb6497bfebdd1eaeaf74

felixge

$ go tool compile -S main.go
main.main STEXT size=64 args=0x0 locals=0x8 funcid=0x0 align=0x0
	0x0000 00000 (main.go:3)	TEXT	main.main(SB), ABIInternal, $16-0
	0x0000 00000 (main.go:3)	MOVD	16(g), R16
	0x0004 00004 (main.go:3)	PCDATA	$0, $-2
	0x0004 00004 (main.go:3)	CMP	R16, RSP
	0x0008 00008 (main.go:3)	BLS	40
	0x000c 00012 (main.go:3)	PCDATA	$0, $-1
	0x000c 00012 (main.go:3)	MOVD.W	R30, -16(RSP)
	0x0010 00016 (main.go:3)	MOVD	R29, -8(RSP)

felixge

All results are based on my patch against the sweet benchmarks.

• baseline is HEAD^ with tracing disabled.
• gentraceback is HEAD^ with tracing enabled (-trace).
• fpcallers is HEAD with tracing enabled (-trace).

felixge

package main

import (
	"bytes"
	"compress/gzip"
	"io"
	"os"
	"testing"
)

felixge

$ curl 'http://169.254.169.254/latest/meta-data/instance-type'
c6g.metal
$ go version
go version go1.19.3 linux/arm64
$ go test -run='^$' -cpu=1,2,4,8,16,32,64 -bench . -count=30 -timeout=0 | tee bench.txt
$ benchstat bench.txt | tee benchstat.txt

felixge

diff --git a/src/runtime/pprof/pprof_test.go b/src/runtime/pprof/pprof_test.go
index 1947edf44a..f474036ccf 100644
--- a/src/runtime/pprof/pprof_test.go
+++ b/src/runtime/pprof/pprof_test.go
@@ -1435,49 +1435,25 @@ func TestLabelSystemstack(t *testing.T) {
        // Two conditions to check:
        // * labelHog should always be labeled.
        // * The label should _only_ appear on labelHog and the Do call above.
-       for _, s := range p.Sample {
+       _true, _false := true, false

felixge

{"version":0,"package":"main","goos":"darwin","goarch":"amd64","gc_version":"go1.17.2","file":"/Users/felix.geisendoerfer/go/src/github.com/felixge/dump/inline-test/main.go"}
{"range":{"start":{"line":5,"character":6},"end":{"line":5,"character":6}},"severity":3,"code":"canInlineFunction","source":"go compiler","message":"cost: 59"}
{"range":{"start":{"line":9,"character":6},"end":{"line":9,"character":6}},"severity":3,"code":"cannotInlineFunction","source":"go compiler","message":"function too complex: cost 88 exceeds budget 80"}
{"range":{"start":{"line":11,"character":15},"end":{"line":11,"character":15}},"severity":3,"code":"escape","source":"go compiler","message":"\"Hello World\" escapes to heap","relatedInformation":[{"location":{"uri":"file:///Users/felix.geisendoerfer/go/src/github.com/felixge/dump/inline-test/main.go","range":{"start":{"line":11,"character":15},"end":{"line":11,"character":15}}},"message":"escflow:    flow: ~arg0 = \u0026{storage for \"Hello World\"}:"},{"location":{"uri":"file:///U

felixge

{
  "flameExplain": "Go to flame-explain.com and paste this JSON in the Input tab.",
  "input": {
    "plan": "[\n  {\n    \"Plan\": {\n      \"Node Type\": \"Function Scan\",\n      \"Parallel Aware\": false,\n      \"Function Name\": \"generate_series\",\n      \"Schema\": \"pg_catalog\",\n      \"Alias\": \"generate_series\",\n      \"Startup Cost\": 0.00,\n      \"Total Cost\": 10.00,\n      \"Plan Rows\": 1000,\n      \"Plan Width\": 4,\n      \"Actual Startup Time\": 194.503,\n      \"Actual Total Time\": 331.185,\n      \"Actual Rows\": 1500000,\n      \"Actual Loops\": 1,\n      \"Output\": [\"generate_series\"],\n      \"Function Call\": \"generate_series(1, 1500000)\",\n      \"Shared Hit Blocks\": 0,\n      \"Shared Read Blocks\": 0,\n      \"Shared Dirtied Blocks\": 0,\n      \"Shared Written Blocks\": 0,\n      \"Local Hit Blocks\": 0,\n      \"Local Read Blocks\": 0,\n      \"Local Dirtied Blocks\": 0,\n      \"Local Written Blocks\": 0,\n      \"Temp Read Blocks\": 0,\n      \"Temp Written Bloc