andreacavalli/rocksdb
0
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Remove double buffering on RandomRead on Windows.

Browse Source 
Summary:
Remove double buffering on RandomRead on Windows.
  With more logic appear in file reader/write Read no longer
  obeys forwarding calls to Windows implementation.
  Previously direct_io (unbuffered) was only available on Windows
  but now is supported as generic.
  We remove intermediate buffering on Windows.
  Remove random_access_max_buffer_size option which was windows specific.
  Non-zero values for that opton introduced unnecessary lock contention.
  Remove Env::EnableReadAhead(), Env::ShouldForwardRawRequest() that are
  no longer necessary.
  Add aligned buffer reads for cases when requested reads exceed read ahead size.
Closes https://github.com/facebook/rocksdb/pull/2105

Differential Revision: D4847770

Pulled By: siying

fbshipit-source-id: 8ab48f8e854ab498a4fd398a6934859792a2788f
This commit is contained in:
Dmitri Smirnov 2017-04-27 12:19:55 -07:00 committed by Facebook Github Bot
parent e15382c09c
commit cdad04b051
10 changed files with 32 additions and 311 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
HISTORY.md
View File

@ -7,6 +7,8 @@
## 5.4.0 (04/11/2017)
### Public API Change
* random_access_max_buffer_size no longer has any effect
* Removed Env::EnableReadAhead(), Env::ShouldForwardRawRequest()
* Support dynamically change `stats_dump_period_sec` option via SetDBOptions().
* Added ReadOptions::max_skippable_internal_keys to set a threshold to fail a request as incomplete when too many keys are being skipped when using iterators.
* DB::Get in place of std::string accepts PinnableSlice, which avoids the extra memcpy of value to std::string in most of cases.

1
db/compaction_iterator.cc
View File

@ -6,6 +6,7 @@
// of patent rights can be found in the PATENTS file in the same directory.
#include "db/compaction_iterator.h"
#include "rocksdb/listener.h"
#include "table/internal_iterator.h"
namespace rocksdb {

21
include/rocksdb/env.h
View File

@ -510,16 +510,6 @@ class RandomAccessFile {
return Status::OK();
}
// Used by the file_reader_writer to decide if the ReadAhead wrapper
// should simply forward the call and do not enact buffering or locking.
virtual bool ShouldForwardRawRequest() const {
return false;
}
// For cases when read-ahead is implemented in the platform dependent
// layer
virtual void EnableReadAhead() {}
// Tries to get an unique ID for this file that will be the same each time
// the file is opened (and will stay the same while the file is open).
// Furthermore, it tries to make this ID at most "max_size" bytes. If such an
@ -751,17 +741,6 @@ class RandomRWFile {
// aligned buffer for Direct I/O
virtual size_t GetRequiredBufferAlignment() const { return kDefaultPageSize; }
// Used by the file_reader_writer to decide if the ReadAhead wrapper
// should simply forward the call and do not enact read_ahead buffering or locking.
// The implementation below takes care of reading ahead
virtual bool ShouldForwardRawRequest() const {
return false;
}
// For cases when read-ahead is implemented in the platform dependent
// layer. This is when ShouldForwardRawRequest() returns true.
virtual void EnableReadAhead() {}
// Write bytes in `data` at offset `offset`, Returns Status::OK() on success.
// Pass aligned buffer when use_direct_io() returns true.
virtual Status Write(uint64_t offset, const Slice& data) = 0;

6
options/options_settable_test.cc
View File

@ -45,7 +45,7 @@ namespace rocksdb {
// settable through string on limited platforms as it depends on behavior of
// compilers.
#ifndef ROCKSDB_LITE
#ifdef OS_LINUX
#if defined OS_LINUX || defined OS_WIN
#ifndef __clang__
class OptionsSettableTest : public testing::Test {
@ -54,7 +54,7 @@ class OptionsSettableTest : public testing::Test {
};
const char kSpecialChar = 'z';
typedef std::vector<std::pair<int, size_t>> OffsetGap;
typedef std::vector<std::pair<size_t, size_t>> OffsetGap;
void FillWithSpecialChar(char* start_ptr, size_t total_size,
const OffsetGap& blacklist) {
@ -446,7 +446,7 @@ TEST_F(OptionsSettableTest, ColumnFamilyOptionsAllFieldsSettable) {
delete[] new_options_ptr;
}
#endif // !__clang__
#endif // OS_LINUX
#endif // OS_LINUX || OS_WIN
#endif // !ROCKSDB_LITE
} // namespace rocksdb

206
port/win/io_win.cc
View File

@ -638,71 +638,6 @@ Status WinSequentialFile::InvalidateCache(size_t offset, size_t length) {
//////////////////////////////////////////////////////////////////////////////////////////////////
/// WinRandomAccessBase
// Helper
void CalculateReadParameters(size_t alignment, uint64_t offset,
size_t bytes_requested,
size_t& actual_bytes_toread,
uint64_t& first_page_start) {
first_page_start = TruncateToPageBoundary(alignment, offset);
const uint64_t last_page_start =
TruncateToPageBoundary(alignment, offset + bytes_requested - 1);
actual_bytes_toread = (last_page_start - first_page_start) + alignment;
}
SSIZE_T WinRandomAccessImpl::ReadIntoBuffer(uint64_t user_offset,
uint64_t first_page_start,
size_t bytes_to_read, size_t& left,
AlignedBuffer& buffer, char* dest) const {
assert(buffer.CurrentSize() == 0);
assert(buffer.Capacity() >= bytes_to_read);
SSIZE_T read =
PositionedReadInternal(buffer.Destination(), bytes_to_read,
first_page_start);
if (read > 0) {
buffer.Size(read);
// Let's figure out how much we read from the users standpoint
if ((first_page_start + buffer.CurrentSize()) > user_offset) {
assert(first_page_start <= user_offset);
size_t buffer_offset = user_offset - first_page_start;
read = buffer.Read(dest, buffer_offset, left);
} else {
read = 0;
}
left -= read;
}
return read;
}
SSIZE_T WinRandomAccessImpl::ReadIntoOneShotBuffer(uint64_t user_offset,
uint64_t first_page_start,
size_t bytes_to_read, size_t& left,
char* dest) const {
AlignedBuffer bigBuffer;
bigBuffer.Alignment(buffer_.Alignment());
bigBuffer.AllocateNewBuffer(bytes_to_read);
return ReadIntoBuffer(user_offset, first_page_start, bytes_to_read, left,
bigBuffer, dest);
}
SSIZE_T WinRandomAccessImpl::ReadIntoInstanceBuffer(uint64_t user_offset,
uint64_t first_page_start,
size_t bytes_to_read, size_t& left,
char* dest) const {
SSIZE_T read = ReadIntoBuffer(user_offset, first_page_start, bytes_to_read,
left, buffer_, dest);
if (read > 0) {
buffered_start_ = first_page_start;
}
return read;
}
SSIZE_T WinRandomAccessImpl::PositionedReadInternal(char* src,
size_t numBytes,
uint64_t offset) const {
@ -714,17 +649,9 @@ WinRandomAccessImpl::WinRandomAccessImpl(WinFileData* file_base,
size_t alignment,
const EnvOptions& options) :
file_base_(file_base),
read_ahead_(false),
compaction_readahead_size_(options.compaction_readahead_size),
random_access_max_buffer_size_(options.random_access_max_buffer_size),
buffer_(),
buffered_start_(0) {
alignment_(alignment) {
assert(!options.use_mmap_reads);
// Do not allocate the buffer either until the first request or
// until there is a call to allocate a read-ahead buffer
buffer_.Alignment(alignment);
}
inline
@ -732,94 +659,26 @@ Status WinRandomAccessImpl::ReadImpl(uint64_t offset, size_t n, Slice* result,
char* scratch) const {
Status s;
SSIZE_T r = -1;
size_t left = n;
char* dest = scratch;
// Check buffer alignment
if (file_base_->use_direct_io()) {
if (!IsAligned(alignment_, scratch)) {
return Status::InvalidArgument("WinRandomAccessImpl::ReadImpl: scratch is not properly aligned");
}
}
if (n == 0) {
*result = Slice(scratch, 0);
return s;
}
// When in direct I/O mode we need to do the following changes:
// - use our own aligned buffer
// - always read at the offset of that is a multiple of alignment
if (file_base_->use_direct_io()) {
uint64_t first_page_start = 0;
size_t actual_bytes_toread = 0;
size_t bytes_requested = left;
size_t left = n;
char* dest = scratch;
if (!read_ahead_ && random_access_max_buffer_size_ == 0) {
CalculateReadParameters(buffer_.Alignment(), offset, bytes_requested,
actual_bytes_toread,
first_page_start);
assert(actual_bytes_toread > 0);
r = ReadIntoOneShotBuffer(offset, first_page_start,
actual_bytes_toread, left, dest);
} else {
std::unique_lock<std::mutex> lock(buffer_mut_);
// Let's see if at least some of the requested data is already
// in the buffer
if (offset >= buffered_start_ &&
offset < (buffered_start_ + buffer_.CurrentSize())) {
size_t buffer_offset = offset - buffered_start_;
r = buffer_.Read(dest, buffer_offset, left);
assert(r >= 0);
left -= size_t(r);
offset += r;
dest += r;
}
// Still some left or none was buffered
if (left > 0) {
// Figure out the start/end offset for reading and amount to read
bytes_requested = left;
if (read_ahead_ && bytes_requested < compaction_readahead_size_) {
bytes_requested = compaction_readahead_size_;
}
CalculateReadParameters(buffer_.Alignment(), offset, bytes_requested,
actual_bytes_toread,
first_page_start);
assert(actual_bytes_toread > 0);
if (buffer_.Capacity() < actual_bytes_toread) {
// If we are in read-ahead mode or the requested size
// exceeds max buffer size then use one-shot
// big buffer otherwise reallocate main buffer
if (read_ahead_ ||
(actual_bytes_toread > random_access_max_buffer_size_)) {
// Unlock the mutex since we are not using instance buffer
lock.unlock();
r = ReadIntoOneShotBuffer(offset, first_page_start,
actual_bytes_toread, left, dest);
} else {
buffer_.AllocateNewBuffer(actual_bytes_toread);
r = ReadIntoInstanceBuffer(offset, first_page_start,
actual_bytes_toread, left, dest);
}
} else {
buffer_.Clear();
r = ReadIntoInstanceBuffer(offset, first_page_start,
actual_bytes_toread, left, dest);
}
}
}
} else {
r = PositionedReadInternal(scratch, left, offset);
if (r > 0) {
left -= r;
}
}
if (r < 0) {
SSIZE_T r = PositionedReadInternal(scratch, left, offset);
if (r > 0) {
left -= r;
} else if (r < 0) {
auto lastError = GetLastError();
// Posix impl wants to treat reads from beyond
// of the file as OK.
@ -833,23 +692,6 @@ Status WinRandomAccessImpl::ReadImpl(uint64_t offset, size_t n, Slice* result,
return s;
}
inline
void WinRandomAccessImpl::HintImpl(RandomAccessFile::AccessPattern pattern) {
if (pattern == RandomAccessFile::SEQUENTIAL && file_base_->use_direct_io() &&
compaction_readahead_size_ > 0) {
std::lock_guard<std::mutex> lg(buffer_mut_);
if (!read_ahead_) {
read_ahead_ = true;
// This would allocate read-ahead size + 2 alignments
// - one for memory alignment which added implicitly by AlignedBuffer
// - We add one more alignment because we will read one alignment more
// from disk
buffer_.AllocateNewBuffer(compaction_readahead_size_ +
buffer_.Alignment());
}
}
}
///////////////////////////////////////////////////////////////////////////////////////////////////
/// WinRandomAccessFile
@ -867,18 +709,6 @@ Status WinRandomAccessFile::Read(uint64_t offset, size_t n, Slice* result,
return ReadImpl(offset, n, result, scratch);
}
void WinRandomAccessFile::EnableReadAhead() {
HintImpl(SEQUENTIAL);
}
bool WinRandomAccessFile::ShouldForwardRawRequest() const {
return true;
}
void WinRandomAccessFile::Hint(AccessPattern pattern) {
HintImpl(pattern);
}
Status WinRandomAccessFile::InvalidateCache(size_t offset, size_t length) {
return Status::OK();
}
@ -1136,14 +966,6 @@ size_t WinRandomRWFile::GetRequiredBufferAlignment() const {
return GetAlignement();
}
bool WinRandomRWFile::ShouldForwardRawRequest() const {
return true;
}
void WinRandomRWFile::EnableReadAhead() {
HintImpl(RandomAccessFile::SEQUENTIAL);
}
Status WinRandomRWFile::Write(uint64_t offset, const Slice & data) {
return PositionedAppendImpl(data, offset);
}

64
port/win/io_win.h
View File

@ -237,54 +237,12 @@ class WinMmapFile : private WinFileData, public WritableFile {
class WinRandomAccessImpl {
protected:
WinFileData* file_base_;
bool read_ahead_;
const size_t compaction_readahead_size_;
const size_t random_access_max_buffer_size_;
mutable std::mutex buffer_mut_;
mutable AlignedBuffer buffer_;
mutable uint64_t
buffered_start_; // file offset set that is currently buffered
size_t alignment_;
// Override for behavior change when creating a custom env
virtual SSIZE_T PositionedReadInternal(char* src, size_t numBytes,
uint64_t offset) const;
/*
* The function reads a requested amount of bytes into the specified aligned
* buffer Upon success the function sets the length of the buffer to the
* amount of bytes actually read even though it might be less than actually
* requested. It then copies the amount of bytes requested by the user (left)
* to the user supplied buffer (dest) and reduces left by the amount of bytes
* copied to the user buffer
*
* @user_offset [in] - offset on disk where the read was requested by the user
* @first_page_start [in] - actual page aligned disk offset that we want to
* read from
* @bytes_to_read [in] - total amount of bytes that will be read from disk
* which is generally greater or equal to the amount
* that the user has requested due to the
* either alignment requirements or read_ahead in
* effect.
* @left [in/out] total amount of bytes that needs to be copied to the user
* buffer. It is reduced by the amount of bytes that actually
* copied
* @buffer - buffer to use
* @dest - user supplied buffer
*/
SSIZE_T ReadIntoBuffer(uint64_t user_offset, uint64_t first_page_start,
size_t bytes_to_read, size_t& left,
AlignedBuffer& buffer, char* dest) const;
SSIZE_T ReadIntoOneShotBuffer(uint64_t user_offset, uint64_t first_page_start,
size_t bytes_to_read, size_t& left,
char* dest) const;
SSIZE_T ReadIntoInstanceBuffer(uint64_t user_offset,
uint64_t first_page_start,
size_t bytes_to_read, size_t& left,
char* dest) const;
WinRandomAccessImpl(WinFileData* file_base, size_t alignment,
const EnvOptions& options);
@ -293,9 +251,7 @@ class WinRandomAccessImpl {
Status ReadImpl(uint64_t offset, size_t n, Slice* result,
char* scratch) const;
void HintImpl(RandomAccessFile::AccessPattern pattern);
size_t GetAlignment() const { return buffer_.Alignment(); }
size_t GetAlignment() const { return alignment_; }
public:
@ -318,14 +274,8 @@ class WinRandomAccessFile
virtual Status Read(uint64_t offset, size_t n, Slice* result,
char* scratch) const override;
virtual bool ShouldForwardRawRequest() const override;
virtual void EnableReadAhead() override;
virtual size_t GetUniqueId(char* id, size_t max_size) const override;
virtual void Hint(AccessPattern pattern) override;
virtual bool use_direct_io() const override { return WinFileData::use_direct_io(); }
virtual Status InvalidateCache(size_t offset, size_t length) override;
@ -449,16 +399,6 @@ class WinRandomRWFile : private WinFileData,
// buffer for Write() when use_direct_io() returns true
virtual size_t GetRequiredBufferAlignment() const override;
// Used by the file_reader_writer to decide if the ReadAhead wrapper
// should simply forward the call and do not enact read_ahead buffering or
// locking.
// The implementation below takes care of reading ahead
virtual bool ShouldForwardRawRequest() const override;
// For cases when read-ahead is implemented in the platform dependent
// layer. This is when ShouldForwardRawRequest() returns true.
virtual void EnableReadAhead() override;
// Write bytes in `data` at offset `offset`, Returns Status::OK() on success.
// Pass aligned buffer when use_direct_io() returns true.
virtual Status Write(uint64_t offset, const Slice& data) override;

6
util/aligned_buffer.h
View File

@ -125,7 +125,11 @@ public:
size_t Read(char* dest, size_t offset, size_t read_size) const {
assert(offset < cursize_);
size_t to_read = std::min(cursize_ - offset, read_size);
size_t to_read = 0;
if(offset < cursize_) {
to_read = std::min(cursize_ - offset, read_size);
}
if (to_read > 0) {
memcpy(dest, bufstart_ + offset, to_read);
}

22
util/file_reader_writer.cc
View File

@ -435,16 +435,12 @@ class ReadaheadRandomAccessFile : public RandomAccessFile {
: file_(std::move(file)),
alignment_(file_->GetRequiredBufferAlignment()),
readahead_size_(Roundup(readahead_size, alignment_)),
forward_calls_(file_->ShouldForwardRawRequest()),
buffer_(),
buffer_offset_(0),
buffer_len_(0) {
if (!forward_calls_) {
buffer_.Alignment(alignment_);
buffer_.AllocateNewBuffer(readahead_size_);
} else if (readahead_size_ > 0) {
file_->EnableReadAhead();
}
buffer_.Alignment(alignment_);
buffer_.AllocateNewBuffer(readahead_size_);
}
ReadaheadRandomAccessFile(const ReadaheadRandomAccessFile&) = delete;
@ -453,15 +449,8 @@ class ReadaheadRandomAccessFile : public RandomAccessFile {
virtual Status Read(uint64_t offset, size_t n, Slice* result,
char* scratch) const override {
if (n + alignment_ >= readahead_size_) {
return file_->Read(offset, n, result, scratch);
}
// On Windows in unbuffered mode this will lead to double buffering
// and double locking so we avoid that.
// In normal mode Windows caches so much data from disk that we do
// not need readahead.
if (forward_calls_) {
if (n + alignment_ >= readahead_size_) {
return file_->Read(offset, n, result, scratch);
}
@ -469,7 +458,7 @@ class ReadaheadRandomAccessFile : public RandomAccessFile {
size_t cached_len = 0;
// Check if there is a cache hit, means that [offset, offset + n) is either
// complitely or partially in the buffer
// completely or partially in the buffer
// If it's completely cached, including end of file case when offset + n is
// greater than EOF, return
if (TryReadFromCache(offset, n, &cached_len, scratch) &&
@ -558,7 +547,6 @@ class ReadaheadRandomAccessFile : public RandomAccessFile {
std::unique_ptr<RandomAccessFile> file_;
const size_t alignment_;
size_t readahead_size_;
const bool forward_calls_;
mutable std::mutex lock_;
mutable AlignedBuffer buffer_;

10
utilities/env_librados.cc
View File

@ -219,16 +219,6 @@ public:
return s;
}
// Used by the file_reader_writer to decide if the ReadAhead wrapper
// should simply forward the call and do not enact buffering or locking.
bool ShouldForwardRawRequest() const {
return false;
}
// For cases when read-ahead is implemented in the platform dependent
// layer
void EnableReadAhead() {}
/**
* @brief [brief description]
* @details Get unique id for each file and guarantee this id is different for each file

5
utilities/env_mirror.cc
View File

@ -86,11 +86,6 @@ class RandomAccessFileMirror : public RandomAccessFile {
return as;
}
bool ShouldForwardRawRequest() const {
// NOTE: not verified
return a_->ShouldForwardRawRequest();
}
size_t GetUniqueId(char* id, size_t max_size) const {
// NOTE: not verified
return a_->GetUniqueId(id, max_size);