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Bug 1547452 - LSNG: Refactor Datastore::GetSnapshotInitInfo using a switch statement; r=asuth

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Differential Revision: https://phabricator.services.mozilla.com/D29137
This commit is contained in:
Jan Varga 2019-04-29 06:05:55 +02:00
parent 128af24b07
commit 55c70603a2
1 changed files with 94 additions and 51 deletions
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145
dom/localstorage/ActorsParent.cpp
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@ -4664,20 +4664,6 @@ void Datastore::GetSnapshotInitInfo(const nsString& aKey,
MOZ_ASSERT(!mClosed);
MOZ_ASSERT(!mInUpdateBatch);
nsString value;
int64_t sizeOfKey = 0;
int64_t sizeOfItem = 0;
bool checkKey = false;
if (!aKey.IsVoid()) {
GetItem(aKey, value);
if (!value.IsVoid()) {
sizeOfKey = aKey.Length();
sizeOfItem = sizeOfKey + value.Length();
checkKey = true;
}
}
#ifdef DEBUG
int64_t sizeOfKeys = 0;
int64_t sizeOfItems = 0;
@ -4690,8 +4676,53 @@ void Datastore::GetSnapshotInitInfo(const nsString& aKey,
MOZ_ASSERT(mSizeOfItems == sizeOfItems);
#endif
if (mSizeOfKeys - sizeOfKey <= gSnapshotPrefill) {
if (mSizeOfItems - sizeOfItem <= gSnapshotPrefill) {
// Computes load state optimized for current size of keys and items.
// Zero key length and value can be passed to do a quick initial estimation.
// If computed load state is already AllOrderedItems then excluded key length
// and value length can't make it any better.
auto GetLoadState = [&](auto aKeyLength, auto aValueLength) {
if (mSizeOfKeys - aKeyLength <= gSnapshotPrefill) {
if (mSizeOfItems - aKeyLength - aValueLength <= gSnapshotPrefill) {
return LSSnapshot::LoadState::AllOrderedItems;
}
return LSSnapshot::LoadState::AllOrderedKeys;
}
return LSSnapshot::LoadState::Partial;
};
// Value for given aKey if aKey is not void (can be void too if value doesn't
// exist for given aKey).
nsString value;
// If aKey and value are not void, checkKey will be set to true. Once we find
// an item for given aKey in one of the loops below, checkKey is set to false
// to prevent additional comparison of strings (string implementation compares
// string lengths first to avoid char by char comparison if possible).
bool checkKey = false;
// Avoid additional hash lookup if all ordered items fit into initial prefill
// already.
LSSnapshot::LoadState loadState = GetLoadState(/* aKeyLength */ 0,
/* aValueLength */ 0);
if (loadState != LSSnapshot::LoadState::AllOrderedItems && !aKey.IsVoid()) {
GetItem(aKey, value);
if (!value.IsVoid()) {
// Ok, we have a non void aKey and value.
// We have to watch for aKey during one of the loops below to exclude it
// from the size computation. The super fast mode (AllOrderedItems)
// doesn't have to do that though.
checkKey = true;
// We have to compute load state again because aKey length and value
// length is excluded from the size in this case.
loadState = GetLoadState(aKey.Length(), value.Length());
}
}
switch (loadState) {
case LSSnapshot::LoadState::AllOrderedItems: {
// We're sending all ordered items, we don't need to check keys because
// mOrderedItems must contain a value for aKey if checkKey is true.
@ -4702,8 +4733,10 @@ void Datastore::GetSnapshotInitInfo(const nsString& aKey,
aAddKeyToUnknownItems = false;
aLoadState = LSSnapshot::LoadState::AllOrderedItems;
} else {
break;
}
case LSSnapshot::LoadState::AllOrderedKeys: {
// We don't have enough snapshot budget to send all items, but we do have
// enough to send all of the keys and to make a best effort to populate as
// many values as possible. We send void string values once we run out of
@ -4765,55 +4798,65 @@ void Datastore::GetSnapshotInitInfo(const nsString& aKey,
aAddKeyToUnknownItems = false;
aLoadState = LSSnapshot::LoadState::AllOrderedKeys;
break;
}
} else {
int64_t size = 0;
for (uint32_t index = 0; index < mOrderedItems.Length(); index++) {
const LSItemInfo& item = mOrderedItems[index];
const nsString& key = item.key();
const nsString& value = item.value();
case LSSnapshot::LoadState::Partial: {
int64_t size = 0;
for (uint32_t index = 0; index < mOrderedItems.Length(); index++) {
const LSItemInfo& item = mOrderedItems[index];
if (checkKey && key == aKey) {
checkKey = false;
} else {
size += static_cast<int64_t>(key.Length()) +
static_cast<int64_t>(value.Length());
const nsString& key = item.key();
const nsString& value = item.value();
if (size > gSnapshotPrefill) {
aNextLoadIndex = index;
break;
if (checkKey && key == aKey) {
checkKey = false;
} else {
size += static_cast<int64_t>(key.Length()) +
static_cast<int64_t>(value.Length());
if (size > gSnapshotPrefill) {
aNextLoadIndex = index;
break;
}
}
aLoadedItems.PutEntry(key);
LSItemInfo* itemInfo = aItemInfos.AppendElement();
itemInfo->key() = key;
itemInfo->value() = value;
}
aAddKeyToUnknownItems = false;
if (!aKey.IsVoid()) {
if (value.IsVoid()) {
aAddKeyToUnknownItems = true;
} else if (checkKey) {
// The item wasn't added in the loop above, add it here.
LSItemInfo* itemInfo = aItemInfos.AppendElement();
itemInfo->key() = aKey;
itemInfo->value() = value;
}
}
aLoadedItems.PutEntry(key);
MOZ_ASSERT(aItemInfos.Length() < mOrderedItems.Length());
LSItemInfo* itemInfo = aItemInfos.AppendElement();
itemInfo->key() = key;
itemInfo->value() = value;
break;
}
aAddKeyToUnknownItems = false;
if (!aKey.IsVoid()) {
if (value.IsVoid()) {
aAddKeyToUnknownItems = true;
} else if (checkKey) {
LSItemInfo* itemInfo = aItemInfos.AppendElement();
itemInfo->key() = aKey;
itemInfo->value() = value;
}
}
MOZ_ASSERT(aItemInfos.Length() < mOrderedItems.Length());
aLoadState = LSSnapshot::LoadState::Partial;
default:
MOZ_CRASH("Bad load state value!");
}
aTotalLength = mValues.Count();
aInitialUsage = mUsage;
aPeakUsage = aInitialUsage;
aLoadState = loadState;
}
void Datastore::GetItem(const nsString& aKey, nsString& aValue) const {