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collector: call PdhGetRawCounterArrayW twice to get the correct amount of bytes needed. #2183

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collector: call PdhGetRawCounterArrayW twice to get the correct amount of bytes needed. #2183

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cebdb93
GetRawCounterArray_size
jkroepke Aug 18, 2025
2ba863b
optimize pdh syscalls
jkroepke Aug 24, 2025
44e2257
optimize pdh syscalls
jkroepke Aug 24, 2025
74d8bc7
collector: call PdhGetRawCounterArrayW twice to get the correct amoun…
jkroepke Aug 24, 2025
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1 change: 1 addition & 0 deletions .idea/dictionaries/project.xml
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136 changes: 84 additions & 52 deletions internal/pdh/collector.go
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Original file line number Diff line number Diff line change
Expand Up @@ -301,6 +301,8 @@
)

buf := make([]byte, 1)
// Reuse string cache across collection cycles to reduce allocations
stringCache := make(map[*uint16]string, 64)

for data := range c.collectCh {
err = (func() error {
Expand Down Expand Up @@ -334,42 +336,61 @@
elemValue := reflect.ValueOf(reflect.New(elemType).Interface()).Elem()

indexMap := map[string]int{}
stringMap := map[*uint16]string{}
// Clear and reuse string cache instead of creating new one each time
for k := range stringCache {
delete(stringCache, k)
}

for _, counter := range c.counters {
for _, instance := range counter.Instances {
// Get the info with the current buffer size
bytesNeeded = uint32(cap(buf))

for {
ret := GetRawCounterArray(instance, &bytesNeeded, &itemCount, &buf[0])
// First call: get required buffer size (as per PDH documentation)
bytesNeeded = 0
ret := GetRawCounterArray(instance, &bytesNeeded, &itemCount, nil)

Check failure on line 348 in internal/pdh/collector.go

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missing whitespace above this line (too many statements above if) (wsl_v5)
if ret != MoreData {
if err := NewPdhError(ret); isKnownCounterDataError(err) {
c.logger.Debug("no data for counter instance",
slog.String("counter", counter.Name),
slog.String("object", c.object),
slog.Any("err", err),
)

if ret == ErrorSuccess {
break
}

if err := NewPdhError(ret); ret != MoreData {
if isKnownCounterDataError(err) {
break
}
return fmt.Errorf("GetRawCounterArray size query: %w", NewPdhError(ret))
}

return fmt.Errorf("GetRawCounterArray: %w", err)
// Optimize buffer allocation: grow with headroom to reduce future reallocations
if bytesNeeded > uint32(cap(buf)) {
// Grow buffer with some headroom (minimum 1KB, or 50% larger than needed)
newSize := bytesNeeded
if newSize < 1024 {
newSize = 1024
} else if newSize < 8192 { // For buffers under 8KB, add 50% headroom
newSize = (newSize * 3) / 2
}
buf = make([]byte, newSize)

Check failure on line 372 in internal/pdh/collector.go

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missing whitespace above this line (invalid statement above assign) (wsl_v5)
}

// Second call: get the actual data (as per PDH documentation)
actualBytesNeeded := bytesNeeded
ret = GetRawCounterArray(instance, &actualBytesNeeded, &itemCount, &buf[0])

Check failure on line 377 in internal/pdh/collector.go

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missing whitespace above this line (too many statements above if) (wsl_v5)
if ret != ErrorSuccess {
if err := NewPdhError(ret); isKnownCounterDataError(err) {
c.logger.Debug("no data for counter instance",
slog.String("counter", counter.Name),
slog.String("object", c.object),
slog.Any("err", err),
)

if bytesNeeded <= uint32(cap(buf)) {
return fmt.Errorf("GetRawCounterArray reports buffer too small (%d), but buffer is large enough (%d): %w", uint32(cap(buf)), bytesNeeded, NewPdhError(ret))
break
}

buf = make([]byte, bytesNeeded)
return fmt.Errorf("GetRawCounterArray data retrieval: %w", NewPdhError(ret))
}

items = unsafe.Slice((*RawCounterItem)(unsafe.Pointer(&buf[0])), itemCount)

var (
instanceName string
ok bool
)

for _, item := range items {
if item.RawValue.CStatus != CstatusValidData && item.RawValue.CStatus != CstatusNewData {
c.logger.Debug("skipping counter item with invalid data status",
Expand All @@ -381,9 +402,14 @@
continue
}

if instanceName, ok = stringMap[item.SzName]; !ok {
var (
instanceName string
ok bool
)

if instanceName, ok = stringCache[item.SzName]; !ok {
instanceName = windows.UTF16PtrToString(item.SzName)
stringMap[item.SzName] = instanceName
stringCache[item.SzName] = instanceName
}

if strings.HasSuffix(instanceName, InstanceTotal) && !c.totalCounterRequested {
Expand All @@ -394,12 +420,8 @@
instanceName = InstanceEmpty
}

var (
index int
ok bool
)

if index, ok = indexMap[instanceName]; !ok {
index, indexExists := indexMap[instanceName]
if !indexExists {
index = dv.Len()
indexMap[instanceName] = index

Expand Down Expand Up @@ -468,6 +490,8 @@
)

buf := make([]byte, 1)
// Reuse string cache across collection cycles to reduce allocations
stringCache := make(map[*uint16]string, 64)

for data := range c.collectCh {
err = (func() error {
Expand Down Expand Up @@ -501,33 +525,45 @@
elemValue := reflect.ValueOf(reflect.New(elemType).Interface()).Elem()

indexMap := map[string]int{}
stringMap := map[*uint16]string{}
// Clear and reuse string cache instead of creating new one each time
for k := range stringCache {
delete(stringCache, k)
}

for _, counter := range c.counters {
for _, instance := range counter.Instances {
// Get the info with the current buffer size
bytesNeeded = uint32(cap(buf))

for {
ret := GetFormattedCounterArrayDouble(instance, &bytesNeeded, &itemCount, &buf[0])

if ret == ErrorSuccess {
// First call: get required buffer size (as per PDH documentation)
bytesNeeded = 0
ret := GetFormattedCounterArrayDouble(instance, &bytesNeeded, &itemCount, nil)

Check failure on line 537 in internal/pdh/collector.go

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if ret != MoreData {
if err := NewPdhError(ret); isKnownCounterDataError(err) {
break
}

if err := NewPdhError(ret); ret != MoreData {
if isKnownCounterDataError(err) {
break
}
return fmt.Errorf("GetFormattedCounterArrayDouble size query: %w", NewPdhError(ret))
}

return fmt.Errorf("GetFormattedCounterArrayDouble: %w", err)
// Optimize buffer allocation: grow with headroom to reduce future reallocations
if bytesNeeded > uint32(cap(buf)) {
// Grow buffer with some headroom (minimum 1KB, or 50% larger than needed)
newSize := bytesNeeded
if newSize < 1024 {
newSize = 1024
} else if newSize < 8192 { // For buffers under 8KB, add 50% headroom
newSize = (newSize * 3) / 2
}
buf = make([]byte, newSize)

Check failure on line 555 in internal/pdh/collector.go

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}

if bytesNeeded <= uint32(cap(buf)) {
return fmt.Errorf("GetFormattedCounterArrayDouble reports buffer too small (%d), but buffer is large enough (%d): %w", uint32(cap(buf)), bytesNeeded, NewPdhError(ret))
// Second call: get the actual data (as per PDH documentation)
actualBytesNeeded := bytesNeeded
ret = GetFormattedCounterArrayDouble(instance, &actualBytesNeeded, &itemCount, &buf[0])

Check failure on line 560 in internal/pdh/collector.go

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missing whitespace above this line (too many statements above if) (wsl_v5)
if ret != ErrorSuccess {
if err := NewPdhError(ret); isKnownCounterDataError(err) {
break
}

buf = make([]byte, bytesNeeded)
return fmt.Errorf("GetFormattedCounterArrayDouble data retrieval: %w", NewPdhError(ret))
}

items = unsafe.Slice((*FmtCounterValueItemDouble)(unsafe.Pointer(&buf[0])), itemCount)
Expand All @@ -542,9 +578,9 @@
continue
}

if instanceName, ok = stringMap[item.SzName]; !ok {
if instanceName, ok = stringCache[item.SzName]; !ok {
instanceName = windows.UTF16PtrToString(item.SzName)
stringMap[item.SzName] = instanceName
stringCache[item.SzName] = instanceName
}

if strings.HasSuffix(instanceName, InstanceTotal) && !c.totalCounterRequested {
Expand All @@ -555,12 +591,8 @@
instanceName = InstanceEmpty
}

var (
index int
ok bool
)

if index, ok = indexMap[instanceName]; !ok {
index, indexExists := indexMap[instanceName]
if !indexExists {
index = dv.Len()
indexMap[instanceName] = index

Expand Down
56 changes: 28 additions & 28 deletions internal/pdh/collector_bench_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -28,34 +28,34 @@ import (
type processFull struct {
Name string

ProcessorTime float64 `pdh:"% Processor Time"`
PrivilegedTime float64 `pdh:"% Privileged Time"`
UserTime float64 `pdh:"% User Time"`
CreatingProcessID float64 `pdh:"Creating Process ID"`
ElapsedTime float64 `pdh:"Elapsed Time"`
HandleCount float64 `pdh:"Handle Count"`
IDProcess float64 `pdh:"ID Process"`
IODataBytesSec float64 `pdh:"IO Data Bytes/sec"`
IODataOperationsSec float64 `pdh:"IO Data Operations/sec"`
IOOtherBytesSec float64 `pdh:"IO Other Bytes/sec"`
IOOtherOperationsSec float64 `pdh:"IO Other Operations/sec"`
IOReadBytesSec float64 `pdh:"IO Read Bytes/sec"`
IOReadOperationsSec float64 `pdh:"IO Read Operations/sec"`
IOWriteBytesSec float64 `pdh:"IO Write Bytes/sec"`
IOWriteOperationsSec float64 `pdh:"IO Write Operations/sec"`
PageFaultsSec float64 `pdh:"Page Faults/sec"`
PageFileBytesPeak float64 `pdh:"Page File Bytes Peak"`
PageFileBytes float64 `pdh:"Page File Bytes"`
PoolNonpagedBytes float64 `pdh:"Pool Nonpaged Bytes"`
PoolPagedBytes float64 `pdh:"Pool Paged Bytes"`
PriorityBase float64 `pdh:"Priority Base"`
PrivateBytes float64 `pdh:"Private Bytes"`
ThreadCount float64 `pdh:"Thread Count"`
VirtualBytesPeak float64 `pdh:"Virtual Bytes Peak"`
VirtualBytes float64 `pdh:"Virtual Bytes"`
WorkingSetPrivate float64 `pdh:"Working Set - Private"`
WorkingSetPeak float64 `pdh:"Working Set Peak"`
WorkingSet float64 `pdh:"Working Set"`
ProcessorTime float64 `perfdata:"% Processor Time"`
PrivilegedTime float64 `perfdata:"% Privileged Time"`
UserTime float64 `perfdata:"% User Time"`
CreatingProcessID float64 `perfdata:"Creating Process ID"`
ElapsedTime float64 `perfdata:"Elapsed Time"`
HandleCount float64 `perfdata:"Handle Count"`
IDProcess float64 `perfdata:"ID Process"`
IODataBytesSec float64 `perfdata:"IO Data Bytes/sec"`
IODataOperationsSec float64 `perfdata:"IO Data Operations/sec"`
IOOtherBytesSec float64 `perfdata:"IO Other Bytes/sec"`
IOOtherOperationsSec float64 `perfdata:"IO Other Operations/sec"`
IOReadBytesSec float64 `perfdata:"IO Read Bytes/sec"`
IOReadOperationsSec float64 `perfdata:"IO Read Operations/sec"`
IOWriteBytesSec float64 `perfdata:"IO Write Bytes/sec"`
IOWriteOperationsSec float64 `perfdata:"IO Write Operations/sec"`
PageFaultsSec float64 `perfdata:"Page Faults/sec"`
PageFileBytesPeak float64 `perfdata:"Page File Bytes Peak"`
PageFileBytes float64 `perfdata:"Page File Bytes"`
PoolNonpagedBytes float64 `perfdata:"Pool Nonpaged Bytes"`
PoolPagedBytes float64 `perfdata:"Pool Paged Bytes"`
PriorityBase float64 `perfdata:"Priority Base"`
PrivateBytes float64 `perfdata:"Private Bytes"`
ThreadCount float64 `perfdata:"Thread Count"`
VirtualBytesPeak float64 `perfdata:"Virtual Bytes Peak"`
VirtualBytes float64 `perfdata:"Virtual Bytes"`
WorkingSetPrivate float64 `perfdata:"Working Set - Private"`
WorkingSetPeak float64 `perfdata:"Working Set Peak"`
WorkingSet float64 `perfdata:"Working Set"`
}

func BenchmarkTestCollector(b *testing.B) {
Expand Down
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