Merge #95590

95590: admission: remove soft/moderate load slots r=irfansharif a=irfansharif

We originally introduced these notions in admission control (#78519) for additional threads for Pebble compaction compression. We envisioned granting these "squishy" slots to background activities and permit work only under periods of low load. In working through #86638 (as part of \#75066), we observed experimentally that the moderate-slots count was not sensitive enough to scheduling latency, and consequently latency observed by foreground traffic. Elastic CPU tokens, the kind now being used for backups, offer an alternative to soft slots. We've since replaced uses of soft slots with elastic CPU tokens.

This PR just removes the now dead-code code around soft/moderate load slots (it's better to minimize the number of mechanisms in the admission package). Fixes #88032.

Release note: None

---

First commit is from #95007.

Co-authored-by: irfan sharif <irfanmahmoudsharif@gmail.com>

pkg/server/config.go

@@ -36,7 +36,6 @@ import (
  "github.com/cockroachdb/cockroach/pkg/storage/enginepb"
  "github.com/cockroachdb/cockroach/pkg/ts"
  "github.com/cockroachdb/cockroach/pkg/util"
- "github.com/cockroachdb/cockroach/pkg/util/admission"
  "github.com/cockroachdb/cockroach/pkg/util/envutil"
  "github.com/cockroachdb/cockroach/pkg/util/humanizeutil"
  "github.com/cockroachdb/cockroach/pkg/util/log"
@@ -343,10 +342,6 @@ type KVConfig struct {
  // The value is split evenly between the stores if there are more than one.
  CacheSize int64
 
- // SoftSlotGranter can be optionally passed into a store to allow the store
- // to perform additional CPU bound work.
- SoftSlotGranter *admission.SoftSlotGranter
-
  // TimeSeriesServerConfig contains configuration specific to the time series
  // server.
  TimeSeriesServerConfig ts.ServerConfig
@@ -632,19 +627,6 @@ func (e *Engines) Close() {
  *e = nil
 }
 
-// cpuWorkPermissionGranter implements the pebble.CPUWorkPermissionGranter
-// interface.
-//type cpuWorkPermissionGranter struct {
-//*admission.SoftSlotGranter
-//}
-
-//func (c *cpuWorkPermissionGranter) TryGetProcs(count int) int {
-//return c.TryGetSlots(count)
-//}
-//func (c *cpuWorkPermissionGranter) ReturnProcs(count int) {
-//c.ReturnSlots(count)
-//}
-
 // CreateEngines creates Engines based on the specs in cfg.Stores.
 func (cfg *Config) CreateEngines(ctx context.Context) (Engines, error) {
  engines := Engines(nil)
@@ -775,11 +757,6 @@ func (cfg *Config) CreateEngines(ctx context.Context) (Engines, error) {
  pebbleConfig.Opts.TableCache = tableCache
  pebbleConfig.Opts.MaxOpenFiles = int(openFileLimitPerStore)
  pebbleConfig.Opts.Experimental.MaxWriterConcurrency = 2
- // TODO(jackson): Implement the new pebble.CPUWorkPermissionGranter
- // interface.
- //pebbleConfig.Opts.Experimental.CPUWorkPermissionGranter = &cpuWorkPermissionGranter{
- //cfg.SoftSlotGranter,
- //}
  if storeKnobs.SmallEngineBlocks {
  for i := range pebbleConfig.Opts.Levels {
  pebbleConfig.Opts.Levels[i].BlockSize = 1

pkg/server/server.go

@@ -246,11 +246,6 @@ func NewServer(cfg Config, stopper *stop.Stopper) (*Server, error) {
  admissionOptions.Override(opts)
  }
  gcoords := admission.NewGrantCoordinators(cfg.AmbientCtx, st, admissionOptions, registry)
- ssg, err := admission.MakeSoftSlotGranter(gcoords.Regular)
- if err != nil {
- return nil, errors.Wrap(err, "failed to soft slot granter")
- }
- cfg.SoftSlotGranter = ssg
 
  engines, err := cfg.CreateEngines(ctx)
  if err != nil {

pkg/ts/catalog/chart_catalog.go

@@ -3748,8 +3748,6 @@ var charts = []sectionDescription{
  Metrics: []string{
  "admission.granter.total_slots.kv",
  "admission.granter.used_slots.kv",
- "admission.granter.total_moderate_slots.kv",
- "admission.granter.used_soft_slots.kv",
  "admission.granter.used_slots.sql-leaf-start",
  "admission.granter.used_slots.sql-root-start",
  },

pkg/util/admission/grant_coordinator.go

@@ -272,12 +272,8 @@ var _ CPULoadListener = &GrantCoordinator{}
 
 // Options for constructing GrantCoordinators.
 type Options struct {
- MinCPUSlots int
- MaxCPUSlots int
- // RunnableAlphaOverride is used to override the alpha value used to
- // compute the ewma of the runnable goroutine counts. It is only used
- // during testing. A 0 value indicates that there is no override.
- RunnableAlphaOverride float64
+ MinCPUSlots int
+ MaxCPUSlots int
  SQLKVResponseBurstTokens int64
  SQLSQLResponseBurstTokens int64
  SQLStatementLeafStartWorkSlots int
@@ -434,10 +430,7 @@ func makeRegularGrantCoordinator(
  settings: st,
  minCPUSlots: opts.MinCPUSlots,
  maxCPUSlots: opts.MaxCPUSlots,
- moderateSlotsClamp: opts.MaxCPUSlots,
- runnableAlphaOverride: opts.RunnableAlphaOverride,
  totalSlotsMetric: metrics.KVTotalSlots,
- totalModerateSlotsMetric: metrics.KVTotalModerateSlots,
  cpuLoadShortPeriodDurationMetric: metrics.KVCPULoadShortPeriodDuration,
  cpuLoadLongPeriodDurationMetric: metrics.KVCPULoadLongPeriodDuration,
  slotAdjusterIncrementsMetric: metrics.KVSlotAdjusterIncrements,
@@ -457,10 +450,8 @@ func makeRegularGrantCoordinator(
  kvg := &slotGranter{
  coord: coord,
  workKind: KVWork,
- totalHighLoadSlots: opts.MinCPUSlots,
- totalModerateLoadSlots: opts.MinCPUSlots,
+ totalSlots: opts.MinCPUSlots,
  usedSlotsMetric: metrics.KVUsedSlots,
- usedSoftSlotsMetric: metrics.KVUsedSoftSlots,
  slotsExhaustedDurationMetric: metrics.KVSlotsExhaustedDuration,
  }
 
@@ -500,11 +491,11 @@ func makeRegularGrantCoordinator(
  coord.granters[SQLSQLResponseWork] = tg
 
  sg := &slotGranter{
- coord:  coord,
- workKind:  SQLStatementLeafStartWork,
- totalHighLoadSlots: opts.SQLStatementLeafStartWorkSlots,
- cpuOverload:  kvSlotAdjuster,
- usedSlotsMetric:  metrics.SQLLeafStartUsedSlots,
+ coord: coord,
+ workKind: SQLStatementLeafStartWork,
+ totalSlots:  opts.SQLStatementLeafStartWorkSlots,
+ cpuOverload: kvSlotAdjuster,
+ usedSlotsMetric: metrics.SQLLeafStartUsedSlots,
  }
  wqMetrics = makeWorkQueueMetrics(workKindString(SQLStatementLeafStartWork), registry, admissionpb.NormalPri, admissionpb.LockingPri)
  req = makeRequester(ambientCtx,
@@ -514,11 +505,11 @@ func makeRegularGrantCoordinator(
  coord.granters[SQLStatementLeafStartWork] = sg
 
  sg = &slotGranter{
- coord:  coord,
- workKind:  SQLStatementRootStartWork,
- totalHighLoadSlots: opts.SQLStatementRootStartWorkSlots,
- cpuOverload:  kvSlotAdjuster,
- usedSlotsMetric:  metrics.SQLRootStartUsedSlots,
+ coord: coord,
+ workKind: SQLStatementRootStartWork,
+ totalSlots:  opts.SQLStatementRootStartWorkSlots,
+ cpuOverload: kvSlotAdjuster,
+ usedSlotsMetric: metrics.SQLRootStartUsedSlots,
  }
  wqMetrics = makeWorkQueueMetrics(workKindString(SQLStatementRootStartWork), registry, admissionpb.NormalPri, admissionpb.LockingPri)
  req = makeRequester(ambientCtx,
@@ -585,11 +576,11 @@ func NewGrantCoordinatorSQL(
  coord.granters[SQLSQLResponseWork] = tg
 
  sg := &slotGranter{
- coord:  coord,
- workKind:  SQLStatementLeafStartWork,
- totalHighLoadSlots: opts.SQLStatementLeafStartWorkSlots,
- cpuOverload:  sqlNodeCPU,
- usedSlotsMetric:  metrics.SQLLeafStartUsedSlots,
+ coord: coord,
+ workKind: SQLStatementLeafStartWork,
+ totalSlots:  opts.SQLStatementLeafStartWorkSlots,
+ cpuOverload: sqlNodeCPU,
+ usedSlotsMetric: metrics.SQLLeafStartUsedSlots,
  }
  wqMetrics = makeWorkQueueMetrics(workKindString(SQLStatementLeafStartWork), registry)
  req = makeRequester(ambientCtx,
@@ -599,11 +590,11 @@ func NewGrantCoordinatorSQL(
  coord.granters[SQLStatementLeafStartWork] = sg
 
  sg = &slotGranter{
- coord:  coord,
- workKind:  SQLStatementRootStartWork,
- totalHighLoadSlots: opts.SQLStatementRootStartWorkSlots,
- cpuOverload:  sqlNodeCPU,
- usedSlotsMetric:  metrics.SQLRootStartUsedSlots,
+ coord: coord,
+ workKind: SQLStatementRootStartWork,
+ totalSlots:  opts.SQLStatementRootStartWorkSlots,
+ cpuOverload: sqlNodeCPU,
+ usedSlotsMetric: metrics.SQLRootStartUsedSlots,
  }
  wqMetrics = makeWorkQueueMetrics(workKindString(SQLStatementRootStartWork), registry)
  req = makeRequester(ambientCtx,
@@ -919,21 +910,15 @@ func (coord *GrantCoordinator) SafeFormat(s redact.SafePrinter, verb rune) {
  case KVWork:
  switch g := coord.granters[i].(type) {
  case *slotGranter:
- kvsa := coord.cpuLoadListener.(*kvSlotAdjuster)
- s.Printf(
- "%s%s: used: %d, high(moderate)-total: %d(%d) moderate-clamp: %d", curSep, workKindString(kind),
- g.usedSlots, g.totalHighLoadSlots, g.totalModerateLoadSlots, kvsa.moderateSlotsClamp)
- if g.usedSoftSlots > 0 {
- s.Printf(" used-soft: %d", g.usedSoftSlots)
- }
+ s.Printf("%s%s: used: %d, total: %d", curSep, workKindString(kind), g.usedSlots, g.totalSlots)
  case *kvStoreTokenGranter:
  s.Printf(" io-avail: %d, elastic-disk-bw-tokens-avail: %d", g.availableIOTokens,
  g.elasticDiskBWTokensAvailable)
  }
  case SQLStatementLeafStartWork, SQLStatementRootStartWork:
  if coord.granters[i] != nil {
  g := coord.granters[i].(*slotGranter)
- s.Printf("%s%s: used: %d, total: %d", curSep, workKindString(kind), g.usedSlots, g.totalHighLoadSlots)
+ s.Printf("%s%s: used: %d, total: %d", curSep, workKindString(kind), g.usedSlots, g.totalSlots)
  }
  case SQLKVResponseWork, SQLSQLResponseWork:
  if coord.granters[i] != nil {
@@ -953,8 +938,6 @@ func (coord *GrantCoordinator) SafeFormat(s redact.SafePrinter, verb rune) {
 type GrantCoordinatorMetrics struct {
  KVTotalSlots *metric.Gauge
  KVUsedSlots *metric.Gauge
- KVTotalModerateSlots *metric.Gauge
- KVUsedSoftSlots *metric.Gauge
  KVSlotsExhaustedDuration *metric.Counter
  KVCPULoadShortPeriodDuration *metric.Counter
  KVCPULoadLongPeriodDuration *metric.Counter
@@ -970,12 +953,8 @@ func (GrantCoordinatorMetrics) MetricStruct() {}
 
 func makeGrantCoordinatorMetrics() GrantCoordinatorMetrics {
  m := GrantCoordinatorMetrics{
- KVTotalSlots: metric.NewGauge(totalSlots),
- KVUsedSlots: metric.NewGauge(addName(workKindString(KVWork), usedSlots)),
- // TODO(sumeer): remove moderate load slots and soft slots code and
- // metrics #88032.
- KVTotalModerateSlots: metric.NewGauge(totalModerateSlots),
- KVUsedSoftSlots: metric.NewGauge(usedSoftSlots),
+ KVTotalSlots: metric.NewGauge(totalSlots),
+ KVUsedSlots: metric.NewGauge(addName(workKindString(KVWork), usedSlots)),
  KVSlotsExhaustedDuration: metric.NewCounter(kvSlotsExhaustedDuration),
  KVCPULoadShortPeriodDuration: metric.NewCounter(kvCPULoadShortPeriodDuration),
  KVCPULoadLongPeriodDuration: metric.NewCounter(kvCPULoadLongPeriodDuration),