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mscluster: reuse control buffers and cut per-property allocations (#2673)

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Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>
This commit is contained in:
Jan-Otto Kröpke
2026-10-11 13:52:55 +02:00
committed by GitHub
co-authored by Claude Opus 5.5
parent a8adb6d7bc
commit 930609b0e5
11 changed files with 541 additions and 74 deletions
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internal/headers/clusapi/clusapi.go
+109 -36
View File
@@ -38,6 +38,7 @@ const (
resourceGetType = 0x0100002d
resourceGetClassInfo = 0x0100000d
maxBufferSize = 64 << 20
maxScratchSize = 64 << 10
stateUnknown = ^uint32(0) // ClusterResourceStateUnknown
propertyListBufferSize = 4 << 10
typeBufferSize = 512
@@ -74,7 +75,7 @@ type nativeAPI struct {
enumName func(enum uintptr, index, enumType uint32, deadline time.Time) (objectName, error)
openResource func(cluster uintptr, name objectName) (uintptr, error)
closeResource func(resource uintptr) error
readResource func(resource uintptr, out *Resource, deadline time.Time) error
readResource func(resource uintptr, out *Resource, scratch *controlScratch, deadline time.Time) error
}
//nolint:gochecknoglobals
@@ -158,6 +159,46 @@ type Cluster struct {
handle uintptr
closed bool
running bool
// scratch belongs to the running call, like handle.
scratch controlScratch
}
// controlScratch is the reusable control buffer of a Cluster. Its owner runs
// one control at a time, so no pool is needed. Values parsed from a result,
// such as Property.Data, point into the buffer and are only valid until the
// next control; callers copy them out first.
type controlScratch struct {
buffer []byte
}
// get returns n zeroed bytes, the same contents as a new buffer.
func (s *controlScratch) get(n int) []byte {
if cap(s.buffer) < n {
s.buffer = make([]byte, max(n, propertyListBufferSize))
}
buffer := s.buffer[:n]
clear(buffer)
return buffer
}
// keep holds on to a buffer a control had to grow, up to maxScratchSize, so
// the next object starts with the larger size.
func (s *controlScratch) keep(data []byte) {
if cap(data) > cap(s.buffer) && cap(data) <= maxScratchSize {
s.buffer = data[:cap(data)]
}
}
// resourceControl calls ClusterResourceControl starting with n bytes of the
// scratch buffer. The result is only valid until the next control.
func (s *controlScratch) resourceControl(handle uintptr, code uint32, n int, deadline time.Time) ([]byte, error) {
data, err := resourceBufferIn(handle, code, s.get(n), deadline)
s.keep(data)
return data, err
}
type Resource struct {
@@ -391,7 +432,7 @@ func (c *Cluster) Resources(deadline time.Time) (_ []Resource, resultErr error)
return fmt.Errorf("OpenClusterResourceEx: %w", err)
}
err = api.readResource(handle, &resource, deadline)
err = api.readResource(handle, &resource, &c.scratch, deadline)
if closeErr := api.closeResource(handle); closeErr != nil {
err = errors.Join(err, fmt.Errorf("CloseClusterResource: %w", closeErr))
}
@@ -459,13 +500,13 @@ func enumName(enum uintptr, index, enumType uint32, deadline time.Time) (objectN
// readResource fills the properties of an open resource. Failed properties are
// omitted; the identity is only valid once the state and owner are known.
func readResource(handle uintptr, resource *Resource, deadline time.Time) error {
func readResource(handle uintptr, resource *Resource, scratch *controlScratch, deadline time.Time) error {
var resultErr error
hasType := false
for _, code := range []uint32{resourceGetROCommonProperties, resourceGetCommonProperties} {
data, err := resourceBuffer(handle, code, propertyListBufferSize, deadline)
data, err := scratch.resourceControl(handle, code, propertyListBufferSize, deadline)
if err != nil {
resultErr = errors.Join(resultErr, fmt.Errorf("ClusterResourceControl %#x: %w", code, err))
@@ -479,23 +520,8 @@ func readResource(handle uintptr, resource *Resource, deadline time.Time) error
continue
}
for name, values := range properties {
if len(values) != 1 {
continue
}
if value, err := values[0].DWORD(); err == nil {
resource.Values[name] = value
}
}
// The read-only common Type property is the same resource type name
// that CLUSCTL_RESOURCE_GET_RESOURCE_TYPE returns.
if values := properties["Type"]; len(values) == 1 {
if value, err := values[0].String(); err == nil {
resource.Type = value
hasType = true
}
if copyResourceProperties(resource, properties) {
hasType = true
}
}
@@ -503,7 +529,7 @@ func readResource(handle uintptr, resource *Resource, deadline time.Time) error
name string
code uint32
}{{"Characteristics", resourceGetCharacteristics}, {"Flags", resourceGetFlags}} {
data, err := resourceBuffer(handle, field.code, 4, deadline)
data, err := scratch.resourceControl(handle, field.code, 4, deadline)
switch {
case err != nil:
resultErr = errors.Join(resultErr, fmt.Errorf("%s: %w", field.name, err))
@@ -514,7 +540,7 @@ func readResource(handle uintptr, resource *Resource, deadline time.Time) error
}
}
data, err := resourceBuffer(handle, resourceGetClassInfo, 8, deadline)
data, err := scratch.resourceControl(handle, resourceGetClassInfo, 8, deadline)
if err != nil {
resultErr = errors.Join(resultErr, fmt.Errorf("class information: %w", err))
} else {
@@ -523,7 +549,7 @@ func readResource(handle uintptr, resource *Resource, deadline time.Time) error
// The property lists normally carry the type; only ask separately without it.
if !hasType {
data, err = resourceBuffer(handle, resourceGetType, typeBufferSize, deadline)
data, err = scratch.resourceControl(handle, resourceGetType, typeBufferSize, deadline)
if err != nil {
return errors.Join(resultErr, fmt.Errorf("resource type: %w", err))
}
@@ -544,6 +570,33 @@ func readResource(handle uintptr, resource *Resource, deadline time.Time) error
return resultErr
}
// copyResourceProperties copies the single DWORD values and the type name out
// of a parsed property list, so the list's buffer can be reused. It reports
// whether the list had the type.
func copyResourceProperties(resource *Resource, properties map[string][]Property) bool {
for name, values := range properties {
if len(values) != 1 {
continue
}
if value, ok := values[0].dword(); ok {
resource.Values[name] = value
}
}
// The read-only common Type property is the same resource type name that
// CLUSCTL_RESOURCE_GET_RESOURCE_TYPE returns.
if values := properties["Type"]; len(values) == 1 {
if value, err := values[0].String(); err == nil {
resource.Type = value
return true
}
}
return false
}
// parseResourceClassInfo decodes CLUS_RESOURCE_CLASS_INFO. Some resource DLLs,
// such as the Storage Spaces Direct Health Service, succeed but return only
// the class DWORD without the subclass; the WMI provider reports their
@@ -563,8 +616,10 @@ func parseResourceClassInfo(data []byte) (uint32, uint32) {
return class, subclass
}
func resourceBuffer(handle uintptr, code uint32, size int, deadline time.Time) ([]byte, error) {
return controlBuffer(deadline, size, func(buffer []byte) (uint32, error) {
// resourceBufferIn calls ClusterResourceControl starting with buffer. The
// result may share buffer's memory.
func resourceBufferIn(handle uintptr, code uint32, buffer []byte, deadline time.Time) ([]byte, error) {
return controlBufferIn(deadline, buffer, func(buffer []byte) (uint32, error) {
var (
size uint32
pointer *byte
@@ -597,7 +652,8 @@ func readResourceState(handle uintptr, deadline time.Time) (uint32, string, stri
}
func stateBuffers(deadline time.Time, call func([]uint16, []uint16) (uint32, uint32, uint32, error)) (uint32, string, string, error) {
node, group := make([]uint16, 256), make([]uint16, 256)
units := make([]uint16, 512)
node, group := units[:256:256], units[256:]
for range 16 {
if err := checkDeadline(deadline); err != nil {
@@ -655,15 +711,20 @@ func checkDeadline(deadline time.Time) error {
return nil
}
// controlBuffer starts with a buffer of the expected size, so most controls need
// one RPC. ERROR_MORE_DATA still grows the buffer to the reported size; size 0
// starts with a NULL size probe.
func controlBuffer(deadline time.Time, size int, call func([]byte) (uint32, error)) ([]byte, error) {
var buffer []byte
if size > 0 {
buffer = make([]byte, size)
// newControlBuffer returns a buffer of the expected size, so most controls
// need one RPC; size 0 starts with a NULL size probe.
func newControlBuffer(size int) []byte {
if size <= 0 {
return nil
}
return make([]byte, size)
}
// controlBufferIn calls a control starting with buffer; an empty buffer is a
// NULL size probe. ERROR_MORE_DATA grows the buffer to the reported size,
// within buffer's capacity when it fits. The result may share buffer's memory.
func controlBufferIn(deadline time.Time, buffer []byte, call func([]byte) (uint32, error)) ([]byte, error) {
for range 16 {
if err := checkDeadline(deadline); err != nil {
return nil, err
@@ -675,7 +736,7 @@ func controlBuffer(deadline time.Time, size int, call func([]byte) (uint32, erro
return nil, errors.New("invalid ClusterResourceControl buffer size")
}
buffer = make([]byte, size)
buffer = growBuffer(buffer, int(size))
continue
}
@@ -689,7 +750,7 @@ func controlBuffer(deadline time.Time, size int, call func([]byte) (uint32, erro
return nil, errors.New("invalid ClusterResourceControl buffer size")
}
buffer = make([]byte, size)
buffer = growBuffer(buffer, int(size))
continue
}
@@ -703,3 +764,15 @@ func controlBuffer(deadline time.Time, size int, call func([]byte) (uint32, erro
return nil, errors.New("ClusterResourceControl buffer did not stabilize")
}
// growBuffer returns size zeroed bytes, reusing buffer's capacity when it fits.
func growBuffer(buffer []byte, size int) []byte {
if size > cap(buffer) {
return make([]byte, size)
}
buffer = buffer[:size]
clear(buffer)
return buffer
}