use stack instead of heap memory in ReadBlockContents in some case

Summary:
  When compression is enabled, and blocksize is not too big, use the
  space in stack to hold bytes read from block.

Bencmark:
base version: commit 8f09d53fd1
  malloc: 1.30% -> 0.98%
  free: 1.49% -> 1.07%

Test Plan:
  make all check

Reviewers: ljin, yhchiang, dhruba, igor, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D20679
This commit is contained in:
Feng Zhu 2014-07-30 23:11:59 -07:00
parent 2ea5e78af7
commit b0999011e2

View File

@ -33,6 +33,7 @@ extern const uint64_t kPlainTableMagicNumber;
const uint64_t kLegacyPlainTableMagicNumber = 0;
const uint64_t kPlainTableMagicNumber = 0;
#endif
const uint32_t DefaultStackBufferSize = 5000;
void BlockHandle::EncodeTo(std::string* dst) const {
// Sanity check that all fields have been set
@ -203,40 +204,30 @@ Status ReadFooterFromFile(RandomAccessFile* file,
return footer->DecodeFrom(&footer_input);
}
Status ReadBlockContents(RandomAccessFile* file,
const Footer& footer,
const ReadOptions& options,
const BlockHandle& handle,
BlockContents* result,
Env* env,
bool do_uncompress) {
result->data = Slice();
result->cachable = false;
result->heap_allocated = false;
// Read the block contents as well as the type/crc footer.
// See table_builder.cc for the code that built this structure.
// Read a block and check its CRC
// contents is the result of reading.
// According to the implementation of file->Read, contents may not point to buf
Status ReadBlock(RandomAccessFile* file, const Footer& footer,
const ReadOptions& options, const BlockHandle& handle,
Slice* contents, // result of reading,
char* buf) {
size_t n = static_cast<size_t>(handle.size());
char* buf = new char[n + kBlockTrailerSize];
Slice contents;
PERF_TIMER_AUTO(block_read_time);
Status s = file->Read(handle.offset(), n + kBlockTrailerSize, &contents, buf);
Status s = file->Read(handle.offset(), n + kBlockTrailerSize, contents, buf);
PERF_TIMER_MEASURE(block_read_time);
PERF_COUNTER_ADD(block_read_count, 1);
PERF_COUNTER_ADD(block_read_byte, n + kBlockTrailerSize);
if (!s.ok()) {
delete[] buf;
return s;
}
if (contents.size() != n + kBlockTrailerSize) {
delete[] buf;
if (contents->size() != n + kBlockTrailerSize) {
return Status::Corruption("truncated block read");
}
// Check the crc of the type and the block contents
const char* data = contents.data(); // Pointer to where Read put the data
const char* data = contents->data(); // Pointer to where Read put the data
if (options.verify_checksums) {
uint32_t value = DecodeFixed32(data + n + 1);
uint32_t actual = 0;
@ -255,12 +246,27 @@ Status ReadBlockContents(RandomAccessFile* file,
s = Status::Corruption("block checksum mismatch");
}
if (!s.ok()) {
delete[] buf;
return s;
}
PERF_TIMER_MEASURE(block_checksum_time);
PERF_TIMER_STOP(block_checksum_time);
}
return s;
}
// Decompress a block according to params
// May need to malloc a space for cache usage
Status DecompressBlock(BlockContents* result, size_t block_size,
bool do_uncompress, const char* buf,
const Slice& contents, bool use_stack_buf) {
Status s;
size_t n = block_size;
const char* data = contents.data();
result->data = Slice();
result->cachable = false;
result->heap_allocated = false;
PERF_TIMER_AUTO(block_decompress_time);
rocksdb::CompressionType compression_type =
static_cast<rocksdb::CompressionType>(data[n]);
// If the caller has requested that the block not be uncompressed
@ -269,12 +275,19 @@ Status ReadBlockContents(RandomAccessFile* file,
// File implementation gave us pointer to some other data.
// Use it directly under the assumption that it will be live
// while the file is open.
delete[] buf;
result->data = Slice(data, n);
result->heap_allocated = false;
result->cachable = false; // Do not double-cache
} else {
if (use_stack_buf) {
// Need to allocate space in heap for cache usage
char* new_buf = new char[n];
memcpy(new_buf, buf, n);
result->data = Slice(new_buf, n);
} else {
result->data = Slice(buf, n);
}
result->heap_allocated = true;
result->cachable = true;
}
@ -282,12 +295,73 @@ Status ReadBlockContents(RandomAccessFile* file,
s = Status::OK();
} else {
s = UncompressBlockContents(data, n, result);
delete[] buf;
}
PERF_TIMER_STOP(block_decompress_time);
return s;
}
// Read and Decompress block
// Use buf in stack as temp reading buffer
Status ReadAndDecompressFast(RandomAccessFile* file, const Footer& footer,
const ReadOptions& options,
const BlockHandle& handle, BlockContents* result,
Env* env, bool do_uncompress) {
Status s;
Slice contents;
size_t n = static_cast<size_t>(handle.size());
char buf[DefaultStackBufferSize];
s = ReadBlock(file, footer, options, handle, &contents, buf);
if (!s.ok()) {
return s;
}
s = DecompressBlock(result, n, do_uncompress, buf, contents, true);
if (!s.ok()) {
return s;
}
return s;
}
// Read and Decompress block
// Use buf in heap as temp reading buffer
Status ReadAndDecompress(RandomAccessFile* file, const Footer& footer,
const ReadOptions& options, const BlockHandle& handle,
BlockContents* result, Env* env, bool do_uncompress) {
Status s;
Slice contents;
size_t n = static_cast<size_t>(handle.size());
char* buf = new char[n + kBlockTrailerSize];
s = ReadBlock(file, footer, options, handle, &contents, buf);
if (!s.ok()) {
delete[] buf;
return s;
}
s = DecompressBlock(result, n, do_uncompress, buf, contents, false);
if (!s.ok()) {
delete[] buf;
return s;
}
if (result->data.data() != buf) {
delete[] buf;
}
return s;
}
Status ReadBlockContents(RandomAccessFile* file, const Footer& footer,
const ReadOptions& options, const BlockHandle& handle,
BlockContents* result, Env* env, bool do_uncompress) {
size_t n = static_cast<size_t>(handle.size());
if (do_uncompress && n + kBlockTrailerSize < DefaultStackBufferSize) {
return ReadAndDecompressFast(file, footer, options, handle, result, env,
do_uncompress);
} else {
return ReadAndDecompress(file, footer, options, handle, result, env,
do_uncompress);
}
}
//
// The 'data' points to the raw block contents that was read in from file.
// This method allocates a new heap buffer and the raw block