How does Go's garbage collector work, and what knobs do you have to tune it?

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Tri-color mark and sweep: objects are white (not visited), grey (reachable but children not scanned), or black (fully scanned) Concurrent: GC mark phase runs alongside the program — very short stop-the-world pauses (<1ms) Write barrier: ensures correctness when the mutator (your code) modifies pointers during GC Sweep phase reclaims white objects after mark completes GC is triggered when heap size doubles since last GC (controlled by GOGC) // GOGC: target percentage of heap growth before next GC
// Default: 100 (GC when heap doubles)
// Lower = more frequent GC, less memory usage
// Higher = less frequent GC, more memory usage
// GOGC=off disables GC entirely (use with GOMEMLIMIT)
os.Setenv("GOGC", "200") // or: runtime/debug.SetGCPercent(200)

// GOMEMLIMIT (Go 1.19+): soft memory limit
// Prevents OOM even if GOGC is high
import "runtime/debug"
debug.SetMemoryLimit(512 * 1024 * 1024) // 512MB soft limit

// Manual GC trigger (rarely needed)
runtime.GC()

// Read GC stats
var stats debug.GCStats
debug.ReadGCStats(&stats)
fmt.Println("NumGC:", stats.NumGC)
fmt.Println("PauseTotal:", stats.PauseTotal) Profile first with pprof heap profiles before tuning GC parameters GOGC=off + GOMEMLIMIT: disable time-based GC, rely on memory limit for triggering — good for batch jobs Reduce allocations using sync.Pool for frequently allocated objects Avoid pointer-heavy data structures — GC must trace every pointer Use GODEBUG=gctrace=1 to see GC pause times and heap sizes in logs

How does Go's garbage collector work, and what knobs do you have to tune it?

Go uses a concurrent tri-color mark-and-sweep GC that runs mostly alongside the program. GOGC controls heap growth trigger and GOMEMLIMIT (Go 1.19+) sets a soft memory ceiling.

How does Go's garbage collector work, and what knobs do you have to tune it?

Go uses a concurrent tri-color mark-and-sweep GC that runs mostly alongside the program. GOGC controls heap growth trigger and GOMEMLIMIT (Go 1.19+) sets a soft memory ceiling.

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