What causes "error processing serialized PGO profile: %w" in golang/go?

Regenerate the profile from a pprof CPU profile using the same Go toolchain version

error processing serialized PGO profile: %w

Error message

error processing serialized PGO profile: %w

What it means

When pgo.IsSerialized detects the profile is in Go's serialized format, the compiler calls pgo.FromSerialized to deserialize it. This error wraps any deserialization failure, indicating the serialized data after the header is corrupt, truncated, or incompatible with the current compiler's expected format.

Source

Thrown at src/cmd/compile/internal/pgoir/irgraph.go:139

// New generates a profile-graph from the profile or pre-processed profile.
func New(profileFile string) (*Profile, error) {
	f, err := os.Open(profileFile)
	if err != nil {
		return nil, fmt.Errorf("error opening profile: %w", err)
	}
	defer f.Close()
	r := bufio.NewReader(f)

	isSerialized, err := pgo.IsSerialized(r)
	if err != nil {
		return nil, fmt.Errorf("error processing profile header: %w", err)
	}

	var base *pgo.Profile
	if isSerialized {
		base, err = pgo.FromSerialized(r)
		if err != nil {
			return nil, fmt.Errorf("error processing serialized PGO profile: %w", err)
		}
	} else {
		base, err = pgo.FromPProf(r)
		if err != nil {
			return nil, fmt.Errorf("error processing pprof PGO profile: %w", err)
		}
	}

	if base.TotalWeight == 0 {
		return nil, nil // accept but ignore profile with no samples.
	}

	// Create package-level call graph with weights from profile and IR.
	wg := createIRGraph(base.NamedEdgeMap)

	return &Profile{
		Profile:    base,
		WeightedCG: wg,

View on GitHub (pinned to b6b368adc5)

Solutions

Regenerate the profile from a pprof CPU profile using the same Go toolchain version
Avoid reusing serialized profiles across Go major version upgrades
If using a profile cache, clear it after upgrading Go
Fall back to providing a raw pprof format profile instead of a serialized one

Defensive patterns

Strategy: validation

Validate before calling

// Verify serialized profile compatibility by checking toolchain version
import (
    "os"
    "runtime"
    "strings"
)

func checkSerializedProfileCompat(path string) error {
    // Serialized profiles are version-specific — always regenerate with current toolchain
    goVersion := runtime.Version() // e.g. go1.21.0
    stat, err := os.Stat(path)
    if err != nil {
        return err
    }
    // If the profile is older than 30 days, recommend regeneration
    if time.Since(stat.ModTime()) > 30*24*time.Hour {
        return fmt.Errorf("profile may be stale (generated with older toolchain than %s), regenerate", goVersion)
    }
    return nil
}

Prevention

Never reuse serialized PGO profiles across Go major version upgrades
Regenerate profiles with the same Go version you use for the production build
If caching serialized profiles, invalidate the cache when the Go toolchain changes
Prefer providing raw pprof profiles to the compiler — let it handle serialization

When it happens

Trigger: A file with the correct serialized-format magic header but containing corrupted or incomplete data after the header. A serialized profile generated by a different or incompatible Go compiler version.

Common situations: Using a pre-serialized PGO profile generated by a different Go version (the serialization format may have changed). Profile corruption after generation. Caching serialized profiles across Go version upgrades.

Related errors

AI-assisted analysis of golang/go@b6b368adc5 (2026-08-12). Data as JSON: /api/errors/ea5b4b72c1e30a17. Report an issue: GitHub.