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cmd/utils: default GOGC to 100 and remove the cache based setting for SetMemoryLimit

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jonny rhea 2026-07-14 08:57:51 -05:00
parent c04540a2db
commit 2154ec62bc
1 changed files with 4 additions and 28 deletions
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32
cmd/utils/flags.go
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@ -556,7 +556,7 @@ var (
} }
MemoryLimitFlag = &cli.IntFlag{ MemoryLimitFlag = &cli.IntFlag{
Name: "memorylimit", Name: "memorylimit",
Usage: "Soft memory limit for the Go runtime in megabytes (default = derived from --cache and available memory)", Usage: "Soft memory limit for the Go runtime in megabytes (default = no limit)",
Category: flags.PerfCategory, Category: flags.PerfCategory,
} }
CryptoKZGFlag = &cli.StringFlag{ CryptoKZGFlag = &cli.StringFlag{
@ -1767,36 +1767,12 @@ func SetEthConfig(ctx *cli.Context, stack *node.Node, cfg *ethconfig.Config) {
ctx.Set(CacheFlag.Name, strconv.Itoa(allowance)) ctx.Set(CacheFlag.Name, strconv.Itoa(allowance))
} }
} }
// Tune Go's GC to balance throughput against the database cache.
// godebug.SetGCPercent(100)
// The historical formula here was:
// gogc = max(20, min(100, 100/(cache_GB)))
// which drove GOGC down to 20 at --cache >= 8 GiB. With GOGC=20, the GC
// fires every ~20% heap growth — and during block processing that
// burned ~20% of CPU on `runtime.scanobject`/`gcDrain`/`findObject`
// (confirmed by CPU profile of newPayload).
//
// Modern Go (1.19+) supports SetMemoryLimit, which lets the runtime keep
// GOGC at the default 100 (fewer/larger collections) while still keeping
// memory below a soft cap. We size the cap from the same cgroup-aware
// limit used for the cache sanitizer above (total), so it's large enough
// that GOGC=100 governs steady state but the limit engages under real
// memory pressure. An explicit --memorylimit overrides this and when neither
// is available, Go's defaults are left untouched.
if ctx.IsSet(MemoryLimitFlag.Name) { if ctx.IsSet(MemoryLimitFlag.Name) {
memLimit := int64(ctx.Int(MemoryLimitFlag.Name)) * 1024 * 1024 memLimit := int64(ctx.Int(MemoryLimitFlag.Name)) * 1024 * 1024
log.Debug("Setting Go memory limit", "MB", memLimit/1024/1024, "source", "flag") log.Debug("Setting Go memory limit", "MB", memLimit/1024/1024)
godebug.SetMemoryLimit(memLimit) godebug.SetMemoryLimit(memLimit)
godebug.SetGCPercent(100)
} else if total > 0 {
cache := int64(ctx.Int(CacheFlag.Name)) * 1024 * 1024
// Target ~4x the cache so GOGC=100 governs steady state, but cap at
// half of memory. The rest is for the OS, page cache, and off-heap
// caches like Pebble that SetMemoryLimit doesn't count.
memLimit := min(int64(total)/2, cache*4)
log.Debug("Setting Go memory limit", "MB", memLimit/1024/1024, "source", source)
godebug.SetMemoryLimit(memLimit)
godebug.SetGCPercent(100)
} }
if ctx.IsSet(SyncTargetFlag.Name) { if ctx.IsSet(SyncTargetFlag.Name) {