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Avoid malloc in NotFound key status if no message is given.

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Summary:
In some places we have NotFound status created with empty message, but it doesn't avoid a malloc. With this patch, the malloc is avoided for that case.

The motivation of it is that I found in db_bench readrandom test when all keys are not existing, about 4% of the total running time is spent on malloc of Status, plus a similar amount of CPU spent on free of them, which is not necessary.

Test Plan: make all check

Reviewers: dhruba, haobo, igor

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14691
This commit is contained in:
Siying Dong 2013-12-26 13:49:04 -08:00
parent b40c052bfa
commit 18df47b79a
4 changed files with 64 additions and 60 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
db/memtable.cc
View File

@ -225,7 +225,7 @@ bool MemTable::Get(const LookupKey& key, std::string* value, Status* s,
*s = Status::Corruption("Error: Could not perform merge.");
}
} else {
*s = Status::NotFound(Slice());
*s = Status::NotFound();
}
return true;
}

4
db/version_set.cc
View File

@ -545,7 +545,7 @@ void Version::Get(const ReadOptions& options,
case kFound:
return;
case kDeleted:
*status = Status::NotFound(Slice()); // Use empty error message for speed
*status = Status::NotFound(); // Use empty error message for speed
return;
case kCorrupt:
*status = Status::Corruption("corrupted key for ", user_key);
@ -570,7 +570,7 @@ void Version::Get(const ReadOptions& options,
user_key);
}
} else {
*status = Status::NotFound(Slice()); // Use an empty error message for speed
*status = Status::NotFound(); // Use an empty error message for speed
}
}

31
include/rocksdb/status.h
View File

@ -25,7 +25,7 @@ namespace rocksdb {
class Status {
public:
// Create a success status.
Status() : state_(nullptr) { }
Status() : code_(kOk), state_(nullptr) { }
~Status() { delete[] state_; }
// Copy the specified status.
@ -39,6 +39,10 @@ class Status {
static Status NotFound(const Slice& msg, const Slice& msg2 = Slice()) {
return Status(kNotFound, msg, msg2);
}
// Fast path for not found without malloc;
static Status NotFound() {
return Status(kNotFound);
}
static Status Corruption(const Slice& msg, const Slice& msg2 = Slice()) {
return Status(kCorruption, msg, msg2);
}
@ -59,7 +63,7 @@ class Status {
}
// Returns true iff the status indicates success.
bool ok() const { return (state_ == nullptr); }
bool ok() const { return code() == kOk; }
// Returns true iff the status indicates a NotFound error.
bool IsNotFound() const { return code() == kNotFound; }
@ -87,13 +91,6 @@ class Status {
std::string ToString() const;
private:
// OK status has a nullptr state_. Otherwise, state_ is a new[] array
// of the following form:
// state_[0..3] == length of message
// state_[4] == code
// state_[5..] == message
const char* state_;
enum Code {
kOk = 0,
kNotFound = 1,
@ -105,20 +102,30 @@ class Status {
kIncomplete = 7
};
Code code() const {
return (state_ == nullptr) ? kOk : static_cast<Code>(state_[4]);
}
// A nullptr state_ (which is always the case for OK) means the message
// is empty.
// of the following form:
// state_[0..3] == length of message
// state_[4..] == message
Code code_;
const char* state_;
Code code() const {
return code_;
}
explicit Status(Code code) : code_(code), state_(nullptr) { }
Status(Code code, const Slice& msg, const Slice& msg2);
static const char* CopyState(const char* s);
};
inline Status::Status(const Status& s) {
code_ = s.code_;
state_ = (s.state_ == nullptr) ? nullptr : CopyState(s.state_);
}
inline void Status::operator=(const Status& s) {
// The following condition catches both aliasing (when this == &s),
// and the common case where both s and *this are ok.
code_ = s.code_;
if (state_ != s.state_) {
delete[] state_;
state_ = (s.state_ == nullptr) ? nullptr : CopyState(s.state_);

87
util/status.cc
View File

@ -16,68 +16,65 @@ namespace rocksdb {
const char* Status::CopyState(const char* state) {
uint32_t size;
memcpy(&size, state, sizeof(size));
char* result = new char[size + 5];
memcpy(result, state, size + 5);
char* result = new char[size + 4];
memcpy(result, state, size + 4);
return result;
}
Status::Status(Code code, const Slice& msg, const Slice& msg2) {
Status::Status(Code code, const Slice& msg, const Slice& msg2) :
code_(code) {
assert(code != kOk);
const uint32_t len1 = msg.size();
const uint32_t len2 = msg2.size();
const uint32_t size = len1 + (len2 ? (2 + len2) : 0);
char* result = new char[size + 5];
char* result = new char[size + 4];
memcpy(result, &size, sizeof(size));
result[4] = static_cast<char>(code);
memcpy(result + 5, msg.data(), len1);
memcpy(result + 4, msg.data(), len1);
if (len2) {
result[5 + len1] = ':';
result[6 + len1] = ' ';
memcpy(result + 7 + len1, msg2.data(), len2);
result[4 + len1] = ':';
result[5 + len1] = ' ';
memcpy(result + 6 + len1, msg2.data(), len2);
}
state_ = result;
}
std::string Status::ToString() const {
if (state_ == nullptr) {
return "OK";
} else {
char tmp[30];
const char* type;
switch (code()) {
case kOk:
type = "OK";
break;
case kNotFound:
type = "NotFound: ";
break;
case kCorruption:
type = "Corruption: ";
break;
case kNotSupported:
type = "Not implemented: ";
break;
case kInvalidArgument:
type = "Invalid argument: ";
break;
case kIOError:
type = "IO error: ";
break;
case kMergeInProgress:
type = "Merge In Progress: ";
break;
default:
snprintf(tmp, sizeof(tmp), "Unknown code(%d): ",
static_cast<int>(code()));
type = tmp;
break;
}
std::string result(type);
char tmp[30];
const char* type;
switch (code_) {
case kOk:
return "OK";
case kNotFound:
type = "NotFound: ";
break;
case kCorruption:
type = "Corruption: ";
break;
case kNotSupported:
type = "Not implemented: ";
break;
case kInvalidArgument:
type = "Invalid argument: ";
break;
case kIOError:
type = "IO error: ";
break;
case kMergeInProgress:
type = "Merge In Progress: ";
break;
default:
snprintf(tmp, sizeof(tmp), "Unknown code(%d): ",
static_cast<int>(code()));
type = tmp;
break;
}
std::string result(type);
if (state_ != nullptr) {
uint32_t length;
memcpy(&length, state_, sizeof(length));
result.append(state_ + 5, length);
return result;
result.append(state_ + 4, length);
}
return result;
}
} // namespace rocksdb