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PlainTableBuilder::Add() to use local char array instead of reused std::string as tmp buffer

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Summary: Our profile shows that in one of the applications, 5% of the CPU costs of PlainTableBuilder::Add() are spent on std::string stacks. By this simple change, we avoid this global reusable string. Also, we avoid another call of file appending, which probably gives another 2%.

Test Plan: make all check

Reviewers: haobo, ljin

Reviewed By: haobo

CC: igor, yhchiang, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D17601
This commit is contained in:
sdong 2014-04-09 09:44:23 -07:00
parent b947fdc89d
commit e9ed28f9c8
2 changed files with 20 additions and 14 deletions
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31
table/plain_table_builder.cc
View File

@ -74,10 +74,12 @@ void PlainTableBuilder::Add(const Slice& key, const Slice& value) {
if (!IsFixedLength()) {
// Write key length
key_size_str_.clear();
PutVarint32(&key_size_str_, user_key_size);
file_->Append(key_size_str_);
offset_ += key_size_str_.length();
char key_size_buf[5]; // tmp buffer for key size as varint32
char* ptr = EncodeVarint32(key_size_buf, user_key_size);
assert(ptr <= key_size_buf + sizeof(key_size_buf));
auto len = ptr - key_size_buf;
file_->Append(Slice(key_size_buf, len));
offset_ += len;
}
// Write key
@ -86,25 +88,32 @@ void PlainTableBuilder::Add(const Slice& key, const Slice& value) {
status_ = Status::Corruption(Slice());
return;
}
// For value size as varint32 (up to 5 bytes).
// If the row is of value type with seqId 0, flush the special flag together
// in this buffer to safe one file append call, which takes 1 byte.
char value_size_buf[6];
size_t value_size_buf_size = 0;
if (parsed_key.sequence == 0 && parsed_key.type == kTypeValue) {
file_->Append(Slice(key.data(), user_key_size));
char tmp_char = PlainTableFactory::kValueTypeSeqId0;
file_->Append(Slice(&tmp_char, 1));
offset_ += key.size() - 7;
offset_ += user_key_size;
value_size_buf[0] = PlainTableFactory::kValueTypeSeqId0;
value_size_buf_size = 1;
} else {
file_->Append(key);
offset_ += key.size();
}
// Write value length
value_size_str_.clear();
int value_size = value.size();
PutVarint32(&value_size_str_, value_size);
file_->Append(value_size_str_);
char* end_ptr =
EncodeVarint32(value_size_buf + value_size_buf_size, value_size);
assert(end_ptr <= value_size_buf + sizeof(value_size_buf));
value_size_buf_size = end_ptr - value_size_buf;
file_->Append(Slice(value_size_buf, value_size_buf_size));
// Write value
file_->Append(value);
offset_ += value_size + value_size_str_.length();
offset_ += value_size + value_size_buf_size;
properties_.num_entries++;
properties_.raw_key_size += key.size();

3
table/plain_table_builder.h
View File

@ -69,9 +69,6 @@ private:
const size_t user_key_len_;
bool closed_ = false; // Either Finish() or Abandon() has been called.
std::string key_size_str_;
std::string value_size_str_;
bool IsFixedLength() const {
return user_key_len_ > 0;
}