diff --git a/doc/godebug.md b/doc/godebug.md index 649bcc5982..071acf98cf 100644 --- a/doc/godebug.md +++ b/doc/godebug.md @@ -176,9 +176,6 @@ This behavior is controlled by the `winreadlinkvolume` setting. For Go 1.23, it defaults to `winreadlinkvolume=1`. Previous versions default to `winreadlinkvolume=0`. -Go 1.23 corrected the semantics of contention reports for runtime-internal locks, -and so removed the [`runtimecontentionstacks` setting](/pkg/runtime#hdr-Environment_Variable). - Go 1.23 enabled the experimental post-quantum key exchange mechanism X25519Kyber768Draft00 by default. The default can be reverted using the [`tlskyber` setting](/pkg/crypto/tls/#Config.CurvePreferences). diff --git a/doc/next/6-stdlib/99-minor/runtime/pprof/66999.md b/doc/next/6-stdlib/99-minor/runtime/pprof/66999.md deleted file mode 100644 index 7943b17b15..0000000000 --- a/doc/next/6-stdlib/99-minor/runtime/pprof/66999.md +++ /dev/null @@ -1,5 +0,0 @@ -The mutex profile for contention on runtime-internal locks now correctly points -to the end of the critical section that caused the delay. This matches the -profile's behavior for contention on `sync.Mutex` values. The -`runtimecontentionstacks` setting for `GODEBUG`, which allowed opting in to Go -1.22's unusual behavior for this part of the profile, is now gone. diff --git a/src/runtime/extern.go b/src/runtime/extern.go index 96efcf3273..2019be4dde 100644 --- a/src/runtime/extern.go +++ b/src/runtime/extern.go @@ -159,6 +159,15 @@ It is a comma-separated list of name=val pairs setting these named variables: panicnil: setting panicnil=1 disables the runtime error when calling panic with nil interface value or an untyped nil. + runtimecontentionstacks: setting runtimecontentionstacks=1 enables inclusion of call stacks + related to contention on runtime-internal locks in the "mutex" profile, subject to the + MutexProfileFraction setting. When runtimecontentionstacks=0, contention on + runtime-internal locks will report as "runtime._LostContendedRuntimeLock". When + runtimecontentionstacks=1, the call stacks will correspond to the unlock call that released + the lock. But instead of the value corresponding to the amount of contention that call + stack caused, it corresponds to the amount of time the caller of unlock had to wait in its + original call to lock. A future release is expected to align those and remove this setting. + invalidptr: invalidptr=1 (the default) causes the garbage collector and stack copier to crash the program if an invalid pointer value (for example, 1) is found in a pointer-typed location. Setting invalidptr=0 disables this check. diff --git a/src/runtime/metrics_test.go b/src/runtime/metrics_test.go index fbf19e2b5e..ebbf0e4fd0 100644 --- a/src/runtime/metrics_test.go +++ b/src/runtime/metrics_test.go @@ -6,6 +6,7 @@ package runtime_test import ( "bytes" + "fmt" "internal/abi" "internal/goexperiment" "internal/profile" @@ -954,6 +955,17 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) { t.Fatalf("need MutexProfileRate 0, got %d", old) } + { + before := os.Getenv("GODEBUG") + for _, s := range strings.Split(before, ",") { + if strings.HasPrefix(s, "runtimecontentionstacks=") { + t.Logf("GODEBUG includes explicit setting %q", s) + } + } + defer func() { os.Setenv("GODEBUG", before) }() + os.Setenv("GODEBUG", fmt.Sprintf("%s,runtimecontentionstacks=1", before)) + } + t.Logf("NumCPU %d", runtime.NumCPU()) t.Logf("GOMAXPROCS %d", runtime.GOMAXPROCS(0)) if minCPU := 2; runtime.NumCPU() < minCPU { @@ -1152,7 +1164,7 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) { stks := [][]string{{ "runtime.unlock", - "runtime_test." + name + ".func4.1", + "runtime_test." + name + ".func5.1", "runtime_test.(*contentionWorker).run", }} @@ -1258,14 +1270,14 @@ func TestRuntimeLockMetricsAndProfile(t *testing.T) { { "runtime.unlock", "runtime.semrelease1", - "runtime_test.TestRuntimeLockMetricsAndProfile.func5.1", + "runtime_test.TestRuntimeLockMetricsAndProfile.func6.1", "runtime_test.(*contentionWorker).run", }, { "runtime.unlock", "runtime.semacquire1", "runtime.semacquire", - "runtime_test.TestRuntimeLockMetricsAndProfile.func5.1", + "runtime_test.TestRuntimeLockMetricsAndProfile.func6.1", "runtime_test.(*contentionWorker).run", }, } diff --git a/src/runtime/mprof.go b/src/runtime/mprof.go index fd0a018724..93d49275c9 100644 --- a/src/runtime/mprof.go +++ b/src/runtime/mprof.go @@ -915,6 +915,11 @@ func (prof *mLockProfile) captureStack() { } prof.stack[0] = logicalStackSentinel + if debug.runtimeContentionStacks.Load() == 0 { + prof.stack[1] = abi.FuncPCABIInternal(_LostContendedRuntimeLock) + sys.PCQuantum + prof.stack[2] = 0 + return + } var nstk int gp := getg() diff --git a/src/runtime/pprof/pprof.go b/src/runtime/pprof/pprof.go index 43ef66f0b0..be17e59875 100644 --- a/src/runtime/pprof/pprof.go +++ b/src/runtime/pprof/pprof.go @@ -166,6 +166,12 @@ import ( // holds a lock for 1s while 5 other goroutines are waiting for the entire // second to acquire the lock, its unlock call stack will report 5s of // contention. +// +// Runtime-internal locks are always reported at the location +// "runtime._LostContendedRuntimeLock". More detailed stack traces for +// runtime-internal locks can be obtained by setting +// `GODEBUG=runtimecontentionstacks=1` (see package [runtime] docs for +// caveats). type Profile struct { name string mu sync.Mutex diff --git a/src/runtime/runtime1.go b/src/runtime/runtime1.go index c74f6d2c72..03ef74b8dc 100644 --- a/src/runtime/runtime1.go +++ b/src/runtime/runtime1.go @@ -319,6 +319,7 @@ var debug struct { gctrace int32 invalidptr int32 madvdontneed int32 // for Linux; issue 28466 + runtimeContentionStacks atomic.Int32 scavtrace int32 scheddetail int32 schedtrace int32 @@ -380,6 +381,7 @@ var dbgvars = []*dbgVar{ {name: "madvdontneed", value: &debug.madvdontneed}, {name: "panicnil", atomic: &debug.panicnil}, {name: "profstackdepth", value: &debug.profstackdepth, def: 128}, + {name: "runtimecontentionstacks", atomic: &debug.runtimeContentionStacks}, {name: "sbrk", value: &debug.sbrk}, {name: "scavtrace", value: &debug.scavtrace}, {name: "scheddetail", value: &debug.scheddetail},