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fragments.go
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fragments.go
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// Copyright (C) 2018 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package dependencygraph2
import (
"context"
"fmt"
"math/bits"
"github.com/google/gapid/gapis/api"
)
type FragmentAccess struct {
Node NodeID
Ref api.RefID
Fragment api.Fragment
Mode AccessMode
Deps []NodeID
}
type FragWatcher interface {
OnReadFrag(ctx context.Context, cmdCtx CmdContext, owner api.RefObject, f api.Fragment, v api.RefObject, track bool)
OnWriteFrag(ctx context.Context, cmdCtx CmdContext, owner api.RefObject, f api.Fragment, old api.RefObject, new api.RefObject, track bool)
OnBeginCmd(ctx context.Context, cmdCtx CmdContext)
OnEndCmd(ctx context.Context, cmdCtx CmdContext) map[NodeID][]FragmentAccess
OnBeginSubCmd(ctx context.Context, cmdCtx CmdContext, subCmdCtx CmdContext)
OnEndSubCmd(ctx context.Context, cmdCtx CmdContext)
GetStateRefs() map[api.RefID]RefFrag
}
func NewFragWatcher() *fragWatcher {
return &fragWatcher{
stateRefs: make(map[api.RefID]RefFrag),
pendingFragments: make(map[api.RefID][]api.Fragment),
refWrites: make(map[api.RefID]*refWrites),
refAccesses: newRefAccesses(),
nodeAccesses: make(map[NodeID][]FragmentAccess),
}
}
type RefFrag struct {
RefID api.RefID
Frag api.Fragment
}
type fragWatcher struct {
stateRefs map[api.RefID]RefFrag
pendingFragments map[api.RefID][]api.Fragment
refWrites map[api.RefID]*refWrites
refAccesses refAccesses
nodeAccesses map[NodeID][]FragmentAccess
stats struct {
// The distribution of the number of relevant writes for each complete read
RelevantWriteDist Distribution
}
}
func (b *fragWatcher) OnReadFrag(ctx context.Context, cmdCtx CmdContext,
owner api.RefObject, frag api.Fragment, value api.RefObject, track bool) {
ownerID := owner.RefID()
valueID := value.RefID()
depth := cmdCtx.depth
nodeID := cmdCtx.nodeID
// Ignore reads with nil owner
if ownerID == api.NilRefID {
return
}
// Ignore reads to variables not accessed through an api.State object
if _, ok := b.stateRefs[ownerID]; !ok {
if _, ok := owner.(api.State); ok {
b.stateRefs[ownerID] = RefFrag{api.NilRefID, nil}
} else {
return
}
}
// The value is now (indirectly) reachable through an api.State object.
// Update `StateRefs` so that later reads/writes to fragments of
// `valueRef` are not ignored.
if valueID != api.NilRefID {
if _, ok := b.stateRefs[valueID]; !ok {
b.stateRefs[valueID] = RefFrag{ownerID, frag}
}
}
if !track {
return
}
if ownerFrags, ok := b.refAccesses.Get(ownerID); ok {
// This object has been accessed since the last `Reset`
fa, hasFa := ownerFrags.Get(frag)
if hasFa {
if fa.GetMode(depth, nodeID) != 0 {
// This read is covered by an earlier access by this command
return
}
}
if a, ok := ownerFrags.Get(api.CompleteFragment{}); ok {
if a.GetMode(depth, nodeID) != 0 {
// This read is covered by an earlier complete access by this command
return
}
}
if !hasFa {
// This fragment has not been accessed since the last `Reset`
fa = &fragAccess{}
ownerFrags.Set(frag, fa)
}
// Record the read, so that repeated reads of the same fragment are ignored.
fa.AddRead(depth, nodeID)
} else {
// This object has not been accessed since the last `Reset`.
ownerFrags := newFragAccesses(owner)
fa := &fragAccess{}
fa.AddRead(depth, nodeID)
ownerFrags.Set(frag, fa)
b.refAccesses.Set(ownerID, ownerFrags)
}
// Add this fragment to the set of fragments to be flushed
b.pendingFragments[ownerID] = append(b.pendingFragments[ownerID], frag)
}
func (b *fragWatcher) OnWriteFrag(ctx context.Context, cmdCtx CmdContext,
owner api.RefObject, frag api.Fragment, oldVal api.RefObject, newVal api.RefObject, track bool) {
ownerID := owner.RefID()
newValID := newVal.RefID()
depth := cmdCtx.depth
nodeID := cmdCtx.nodeID
// Ignore writes with nil owner
if ownerID == api.NilRefID {
return
}
// Ignore writes to variables not accessed through an api.State object
if _, ok := b.stateRefs[ownerID]; !ok {
if _, ok := owner.(api.State); ok {
b.stateRefs[ownerID] = RefFrag{api.NilRefID, nil}
} else {
return
}
}
// The value is now (indirectly) reachable through an api.State object.
// Update `StateRefs` so that later reads/writes to fragments of
// `valueRef` are not ignored.
if newValID != api.NilRefID {
if _, ok := b.stateRefs[newValID]; ok {
b.stateRefs[newValID] = RefFrag{ownerID, frag}
}
}
if !track {
return
}
if ownerFrags, ok := b.refAccesses.Get(ownerID); ok {
// This object has been accessed since the last `Reset`
fa, hasFa := ownerFrags.Get(frag)
if hasFa {
if fa.GetMode(depth, nodeID)&ACCESS_WRITE != 0 {
// This write is covered by an earlier write by this command
return
}
}
ca, hasCa := ownerFrags.Get(api.CompleteFragment{})
if hasCa {
if ca.GetMode(depth, nodeID)&ACCESS_WRITE != 0 {
// This write is covered by an earlier complete write by this command
return
}
}
if !hasFa {
// This fragment has not been accessed since the last `Reset`
fa = &fragAccess{}
ownerFrags.Set(frag, fa)
}
if _, ok := frag.(api.CompleteFragment); ok {
// This is a write to the entire object.
// Clear accesses to all fragments.
ownerFrags.ForeachFrag(func(otherFrag api.Fragment, otherAcc *fragAccess) error {
if otherFrag != frag {
otherAcc.Clear()
// Clear pending writes to individual fragments,
// since this will be covered by the complete write
otherAcc.pending &^= ACCESS_WRITE
}
return nil
})
} else {
// `frag` is not CompleteFragment, and the write is not
// covered by any previous writes by this node (neither
// to frag nor to CompleteFragment).
// Clear previous access to this fragment
fa.Clear()
// Clear previous access to the complete fragment, since
// part of that access is invalidated by this read.
if hasCa {
ca.Clear()
}
}
// Record the write, so that later reads/writes covered by this
// write are ignored.
fa.AddWrite(depth, nodeID)
} else {
// This object has not been accessed since the last `Reset`.
ownerFrags := newFragAccesses(owner)
fa := &fragAccess{}
fa.AddWrite(depth, nodeID)
ownerFrags.Set(frag, fa)
b.refAccesses.Set(ownerID, ownerFrags)
}
// Add this fragment to the set of fragments to be flushed
b.pendingFragments[ownerID] = append(b.pendingFragments[ownerID], frag)
}
func (b *fragWatcher) Flush(ctx context.Context, cmdCtx CmdContext) {
nodeID := cmdCtx.nodeID
fragAccesses := b.nodeAccesses[nodeID]
// Compute the maximum possible of size of fragAccesses at the end of `Flush`.
fragAccessesCap := len(fragAccesses)
for _, frags := range b.pendingFragments {
fragAccessesCap += len(frags)
}
// Ensure that fragAccesses has sufficient capacity
if fragAccessesCap > cap(fragAccesses) {
// round up to next power of 2
fragAccessesCap = 1 << uint(bits.Len(uint(fragAccessesCap)))
newFragAccesses := make([]FragmentAccess, len(fragAccesses), fragAccessesCap)
copy(newFragAccesses, fragAccesses)
fragAccesses = newFragAccesses
}
for refID, frags := range b.pendingFragments {
refFrags, _ := b.refAccesses.Get(refID)
writes, hasWrites := b.refWrites[refID]
flushCompleteWrite := func(fa *fragAccess) {
// Write of complete fragment
// => replaces all writes
if writes == nil {
writes = newRefWrites(refFrags.m.EmptyClone())
b.refWrites[refID] = writes
}
writes.frags.Clear()
writes.frags.Set(api.CompleteFragment{}, nodeID)
writes.nodeSlice = []NodeID{nodeID}
writes.nodeSet = map[NodeID]*nodeSetEntry{nodeID: &nodeSetEntry{1, 0}}
fa.pending &^= ACCESS_WRITE
}
flushNonCompleteWrite := func(frag api.Fragment, fa *fragAccess, hasPrevWrite bool, prevWrite NodeID) {
if writes == nil {
writes = newRefWrites(refFrags.m.EmptyClone())
b.refWrites[refID] = writes
}
writes.frags.Set(frag, nodeID)
if prevWrite != nodeID {
if hasPrevWrite {
if e, ok := writes.nodeSet[prevWrite]; ok {
e.count--
if e.count <= 0 {
delete(writes.nodeSet, prevWrite)
i := e.index
l := len(writes.nodeSlice) - 1
if i < l {
writes.nodeSlice[i] = writes.nodeSlice[l]
}
writes.nodeSlice = writes.nodeSlice[:l]
}
}
}
e, ok := writes.nodeSet[nodeID]
if ok {
e.count++
} else {
index := len(writes.nodeSlice)
writes.nodeSlice = append(writes.nodeSlice, nodeID)
e = &nodeSetEntry{1, index}
writes.nodeSet[nodeID] = e
}
}
fa.pending &^= ACCESS_WRITE
}
for _, frag := range frags {
fa, hasFa := refFrags.Get(frag)
_, isComplete := frag.(api.CompleteFragment)
if hasFa && fa.pending != 0 {
writeNodes := []NodeID{}
prevWrite := NodeNoID
hasPrevWrite := false
mode := AccessMode(0)
if hasWrites {
prevWrite, hasPrevWrite = writes.frags.Get(frag)
}
if fa.pending&ACCESS_READ != 0 {
if isComplete {
if hasWrites && len(writes.nodeSlice) > 0 {
writeNodes = make([]NodeID, len(writes.nodeSlice))
copy(writeNodes, writes.nodeSlice)
mode = fa.pending
}
} else if hasPrevWrite {
writeNodes = []NodeID{prevWrite}
mode |= ACCESS_READ
}
fa.pending &^= ACCESS_READ
}
if fa.pending&ACCESS_WRITE != 0 && !isComplete {
flushNonCompleteWrite(frag, fa, hasPrevWrite, prevWrite)
mode |= ACCESS_WRITE
}
if mode != 0 {
fragAccesses = append(fragAccesses, FragmentAccess{
Node: nodeID,
Fragment: frag,
Ref: refID,
Mode: mode,
Deps: writeNodes,
})
}
}
}
ca, hasCa := refFrags.Get(api.CompleteFragment{})
if hasCa && ca.pending&ACCESS_WRITE != 0 {
// Do the complete writes last.
// This handles the cases like the following:
// 1. Read Complete
// 2. Read Single
// 3. Write Complete
// If the 3. is not last, then 2. may be processed incorrectly.
// Note: if the watcher receives any accesses within the
// subcommand after WriteComplete, these are suppressed at the
// OnReadFrag/OnWriteFrag call, and won't be seen here in Flush.
flushCompleteWrite(ca)
ca.pending = 0
}
}
b.nodeAccesses[nodeID] = fragAccesses
b.pendingFragments = make(map[api.RefID][]api.Fragment)
}
func (b *fragWatcher) OnBeginCmd(ctx context.Context, cmdCtx CmdContext) {}
func (b *fragWatcher) OnEndCmd(ctx context.Context, cmdCtx CmdContext) map[NodeID][]FragmentAccess {
b.Flush(ctx, cmdCtx)
acc := b.nodeAccesses
b.pendingFragments = make(map[api.RefID][]api.Fragment)
b.refAccesses = newRefAccesses()
b.nodeAccesses = make(map[NodeID][]FragmentAccess)
return acc
}
func (b *fragWatcher) OnBeginSubCmd(ctx context.Context, cmdCtx CmdContext, subCmdCtx CmdContext) {
b.Flush(ctx, cmdCtx)
}
func (b *fragWatcher) OnEndSubCmd(ctx context.Context, cmdCtx CmdContext) {
b.Flush(ctx, cmdCtx)
}
func (b *fragWatcher) GetStateRefs() map[api.RefID]RefFrag {
return b.stateRefs
}
type nodeSetEntry struct {
count int
index int
}
type refWrites struct {
frags fragWrites
nodeSlice []NodeID
nodeSet map[NodeID]*nodeSetEntry
}
func newRefWrites(frags api.FragmentMap) *refWrites {
return &refWrites{
frags: fragWrites{frags},
nodeSlice: []NodeID{},
nodeSet: make(map[NodeID]*nodeSetEntry),
}
}
type fragWrites struct {
m api.FragmentMap
}
func (w fragWrites) Get(f api.Fragment) (NodeID, bool) {
v, ok := w.m.Get(f)
if ok {
return v.(NodeID), true
}
return NodeNoID, false
}
func (w fragWrites) Set(f api.Fragment, nodeID NodeID) {
w.m.Set(f, nodeID)
}
func (w fragWrites) Clear() {
w.m.Clear()
}
type refAccesses struct {
m map[api.RefID]fragAccesses
}
func newRefAccesses() refAccesses {
return refAccesses{m: make(map[api.RefID]fragAccesses)}
}
func (a refAccesses) Get(ref api.RefID) (fragAccesses, bool) {
if v, ok := a.m[ref]; ok {
return v, true
}
return fragAccesses{}, false
}
func (a refAccesses) Set(ref api.RefID, v fragAccesses) {
a.m[ref] = v
}
type fragAccesses struct {
m api.FragmentMap
}
func newFragAccesses(owner api.RefObject) fragAccesses {
return fragAccesses{owner.NewFragmentMap()}
}
type fragAccess struct {
// Access mode by each subcommand level
accessStack []nodeFragAccess
// Access mode for unflushed accesses
pending AccessMode
}
type nodeFragAccess struct {
node NodeID
mode AccessMode
}
func (a fragAccess) GetMode(depth int, node NodeID) AccessMode {
if depth >= len(a.accessStack) {
return 0
}
v := a.accessStack[depth]
if v.node == node {
return v.mode
}
return 0
}
func (a *fragAccess) grow(depth int) {
if depth >= len(a.accessStack) {
n := 1 << uint(bits.Len(uint(depth)))
newAccessModes := make([]nodeFragAccess, n)
copy(newAccessModes, a.accessStack)
a.accessStack = newAccessModes
}
}
func (a *fragAccess) AddRead(depth int, node NodeID) {
a.grow(depth)
v := &a.accessStack[depth]
if v.node == node {
v.mode |= ACCESS_READ
} else {
v.node = node
v.mode = ACCESS_READ
}
a.pending |= ACCESS_READ
}
func (a *fragAccess) AddWrite(depth int, node NodeID) {
a.grow(depth)
v := &a.accessStack[depth]
if v.node == node {
v.mode |= ACCESS_WRITE
} else {
v.node = node
v.mode = ACCESS_WRITE
}
a.pending |= ACCESS_WRITE
}
func (a *fragAccess) Clear() {
for i := range a.accessStack {
a.accessStack[i] = nodeFragAccess{}
}
}
func (a fragAccesses) Get(f api.Fragment) (*fragAccess, bool) {
if v, ok := a.m.Get(f); ok {
return v.(*fragAccess), true
}
return nil, false
}
func (a fragAccesses) Set(f api.Fragment, v *fragAccess) {
a.m.Set(f, v)
}
func (a fragAccesses) Delete(f api.Fragment) {
a.m.Delete(f)
}
func (a fragAccesses) Clear() {
a.m.Clear()
}
func (a fragAccesses) ForeachFrag(f func(api.Fragment, *fragAccess) error) error {
return a.m.ForeachFrag(func(frag api.Fragment, v interface{}) error {
if fa, ok := v.(*fragAccess); ok {
return f(frag, fa)
}
return fmt.Errorf("fragAccesses FragmentMap contains unexpected value type %T", v)
})
}