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Measure file read latency histogram per level

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Summary: In internal stats, remember read latency histogram, if statistics is enabled. It can be retrieved from DB::GetProperty() with "rocksdb.dbstats" property, if it is enabled.

Test Plan: Manually run db_bench and prints out "rocksdb.dbstats" by hand and make sure it prints out as expected

Reviewers: igor, IslamAbdelRahman, rven, kradhakrishnan, anthony, yhchiang

Reviewed By: yhchiang

Subscribers: MarkCallaghan, leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D44193
This commit is contained in:
sdong 2015-08-13 14:35:54 -07:00
parent b7198c3afe
commit 72613657f0
14 changed files with 109 additions and 48 deletions
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11
db/builder.cc
View file

@ -12,6 +12,7 @@
#include <vector>
#include "db/dbformat.h"
#include "db/filename.h"
#include "db/internal_stats.h"
#include "db/merge_helper.h"
#include "db/table_cache.h"
#include "db/version_edit.h"
@ -54,7 +55,8 @@ Status BuildTable(
const SequenceNumber earliest_seqno_in_memtable,
const CompressionType compression,
const CompressionOptions& compression_opts, bool paranoid_file_checks,
const Env::IOPriority io_priority, TableProperties* table_properties) {
InternalStats* internal_stats, const Env::IOPriority io_priority,
TableProperties* table_properties) {
// Reports the IOStats for flush for every following bytes.
const size_t kReportFlushIOStatsEvery = 1048576;
Status s;
@ -248,8 +250,11 @@ Status BuildTable(
if (s.ok()) {
// Verify that the table is usable
Iterator* it = table_cache->NewIterator(ReadOptions(), env_options,
internal_comparator, meta->fd);
Iterator* it = table_cache->NewIterator(
ReadOptions(), env_options, internal_comparator, meta->fd, nullptr,
(internal_stats == nullptr) ? nullptr
: internal_stats->GetFileReadHist(0),
false);
s = it->status();
if (s.ok() && paranoid_file_checks) {
for (it->SeekToFirst(); it->Valid(); it->Next()) {}

2
db/builder.h
View file

@ -30,6 +30,7 @@ class TableCache;
class VersionEdit;
class TableBuilder;
class WritableFileWriter;
class InternalStats;
TableBuilder* NewTableBuilder(
const ImmutableCFOptions& options,
@ -55,6 +56,7 @@ extern Status BuildTable(
const SequenceNumber earliest_seqno_in_memtable,
const CompressionType compression,
const CompressionOptions& compression_opts, bool paranoid_file_checks,
InternalStats* internal_stats,
const Env::IOPriority io_priority = Env::IO_HIGH,
TableProperties* table_properties = nullptr);

4
db/compaction_job.cc
View file

@ -760,7 +760,9 @@ Status CompactionJob::FinishCompactionOutputFile(const Status& input_status) {
FileDescriptor fd(output_number, output_path_id, current_bytes);
Iterator* iter = cfd->table_cache()->NewIterator(
ReadOptions(), env_options_, cfd->internal_comparator(), fd, nullptr,
true);
cfd->internal_stats()->GetFileReadHist(
compact_->compaction->output_level()),
false);
s = iter->status();
if (s.ok() && paranoid_file_checks_) {

4
db/db_impl.cc
View file

@ -1293,8 +1293,8 @@ Status DBImpl::WriteLevel0TableForRecovery(int job_id, ColumnFamilyData* cfd,
iter.get(), &meta, cfd->internal_comparator(),
cfd->int_tbl_prop_collector_factories(), newest_snapshot,
earliest_seqno_in_memtable, GetCompressionFlush(*cfd->ioptions()),
cfd->ioptions()->compression_opts, paranoid_file_checks, Env::IO_HIGH,
&info.table_properties);
cfd->ioptions()->compression_opts, paranoid_file_checks,
cfd->internal_stats(), Env::IO_HIGH, &info.table_properties);
LogFlush(db_options_.info_log);
Log(InfoLogLevel::DEBUG_LEVEL, db_options_.info_log,
"[%s] [WriteLevel0TableForRecovery]"

16
db/flush_job.cc
View file

@ -232,14 +232,14 @@ Status FlushJob::WriteLevel0Table(const autovector<MemTable*>& mems,
TEST_SYNC_POINT_CALLBACK("FlushJob::WriteLevel0Table:output_compression",
&output_compression_);
s = BuildTable(dbname_, db_options_.env, *cfd_->ioptions(), env_options_,
cfd_->table_cache(), iter.get(), meta,
cfd_->internal_comparator(),
cfd_->int_tbl_prop_collector_factories(), newest_snapshot_,
earliest_seqno_in_memtable, output_compression_,
cfd_->ioptions()->compression_opts,
mutable_cf_options_.paranoid_file_checks, Env::IO_HIGH,
&info.table_properties);
s = BuildTable(
dbname_, db_options_.env, *cfd_->ioptions(), env_options_,
cfd_->table_cache(), iter.get(), meta, cfd_->internal_comparator(),
cfd_->int_tbl_prop_collector_factories(), newest_snapshot_,
earliest_seqno_in_memtable, output_compression_,
cfd_->ioptions()->compression_opts,
mutable_cf_options_.paranoid_file_checks, cfd_->internal_stats(),
Env::IO_HIGH, &info.table_properties);
LogFlush(db_options_.info_log);
}
Log(InfoLogLevel::INFO_LEVEL, db_options_.info_log,

3
db/forward_iterator.cc
View file

@ -47,7 +47,8 @@ class LevelIterator : public Iterator {
assert(file_index_ < files_.size());
file_iter_.reset(cfd_->table_cache()->NewIterator(
read_options_, *(cfd_->soptions()), cfd_->internal_comparator(),
files_[file_index_]->fd, nullptr /* table_reader_ptr */, false));
files_[file_index_]->fd, nullptr /* table_reader_ptr */, nullptr,
false));
}
void SeekToLast() override {
status_ = Status::NotSupported("LevelIterator::SeekToLast()");

10
db/internal_stats.cc
View file

@ -540,6 +540,16 @@ void InternalStats::DumpDBStats(std::string* value) {
10000.0 / std::max(interval_seconds_up, 0.001));
value->append(buf);
for (int level = 0; level < number_levels_; level++) {
if (!file_read_latency_[level].Empty()) {
char buf2[5000];
snprintf(buf2, sizeof(buf2),
"** Level %d read latency histogram (micros):\n%s\n", level,
file_read_latency_[level].ToString().c_str());
value->append(buf2);
}
}
db_stats_snapshot_.seconds_up = seconds_up;
db_stats_snapshot_.ingest_bytes = user_bytes_written;
db_stats_snapshot_.write_other = write_other;

8
db/internal_stats.h
View file

@ -98,6 +98,7 @@ class InternalStats {
comp_stats_(num_levels),
stall_leveln_slowdown_count_hard_(num_levels),
stall_leveln_slowdown_count_soft_(num_levels),
file_read_latency_(num_levels),
bg_error_count_(0),
number_levels_(num_levels),
env_(env),
@ -238,6 +239,10 @@ class InternalStats {
db_stats_[type] += value;
}
HistogramImpl* GetFileReadHist(int level) {
return &file_read_latency_[level];
}
uint64_t GetBackgroundErrorCount() const { return bg_error_count_; }
uint64_t BumpAndGetBackgroundErrorCount() { return ++bg_error_count_; }
@ -265,6 +270,7 @@ class InternalStats {
// These count the number of microseconds for which MakeRoomForWrite stalls.
std::vector<uint64_t> stall_leveln_slowdown_count_hard_;
std::vector<uint64_t> stall_leveln_slowdown_count_soft_;
std::vector<HistogramImpl> file_read_latency_;
// Used to compute per-interval statistics
struct CFStatsSnapshot {
@ -389,6 +395,8 @@ class InternalStats {
void AddDBStats(InternalDBStatsType type, uint64_t value) {}
HistogramImpl* GetFileReadHist(int level) { return nullptr; }
uint64_t GetBackgroundErrorCount() const { return 0; }
uint64_t BumpAndGetBackgroundErrorCount() { return 0; }

2
db/repair.cc
View file

@ -293,7 +293,7 @@ class Repairer {
status = BuildTable(dbname_, env_, ioptions_, env_options_, table_cache_,
iter.get(), &meta, icmp_,
&int_tbl_prop_collector_factories_, 0, 0,
kNoCompression, CompressionOptions(), false);
kNoCompression, CompressionOptions(), false, nullptr);
}
delete mem->Unref();
delete cf_mems_default;

13
db/table_cache.cc
View file

@ -79,7 +79,8 @@ void TableCache::ReleaseHandle(Cache::Handle* handle) {
Status TableCache::FindTable(const EnvOptions& env_options,
const InternalKeyComparator& internal_comparator,
const FileDescriptor& fd, Cache::Handle** handle,
const bool no_io, bool record_read_stats) {
const bool no_io, bool record_read_stats,
HistogramImpl* file_read_hist) {
PERF_TIMER_GUARD(find_table_nanos);
Status s;
uint64_t number = fd.GetNumber();
@ -104,7 +105,7 @@ Status TableCache::FindTable(const EnvOptions& env_options,
new RandomAccessFileReader(
std::move(file), ioptions_.env,
record_read_stats ? ioptions_.statistics : nullptr,
SST_READ_MICROS));
SST_READ_MICROS, file_read_hist));
s = ioptions_.table_factory->NewTableReader(
ioptions_, env_options, internal_comparator, std::move(file_reader),
fd.GetFileSize(), &table_reader);
@ -128,6 +129,7 @@ Iterator* TableCache::NewIterator(const ReadOptions& options,
const InternalKeyComparator& icomparator,
const FileDescriptor& fd,
TableReader** table_reader_ptr,
HistogramImpl* file_read_hist,
bool for_compaction, Arena* arena) {
PERF_TIMER_GUARD(new_table_iterator_nanos);
@ -139,7 +141,8 @@ Iterator* TableCache::NewIterator(const ReadOptions& options,
Status s;
if (table_reader == nullptr) {
s = FindTable(env_options, icomparator, fd, &handle,
options.read_tier == kBlockCacheTier, !for_compaction);
options.read_tier == kBlockCacheTier, !for_compaction,
file_read_hist);
if (!s.ok()) {
return NewErrorIterator(s, arena);
}
@ -164,7 +167,7 @@ Iterator* TableCache::NewIterator(const ReadOptions& options,
Status TableCache::Get(const ReadOptions& options,
const InternalKeyComparator& internal_comparator,
const FileDescriptor& fd, const Slice& k,
GetContext* get_context) {
GetContext* get_context, HistogramImpl* file_read_hist) {
TableReader* t = fd.table_reader;
Status s;
Cache::Handle* handle = nullptr;
@ -210,7 +213,7 @@ Status TableCache::Get(const ReadOptions& options,
if (!t) {
s = FindTable(env_options_, internal_comparator, fd, &handle,
options.read_tier == kBlockCacheTier);
options.read_tier == kBlockCacheTier, file_read_hist);
if (s.ok()) {
t = GetTableReaderFromHandle(handle);
}

7
db/table_cache.h
View file

@ -28,6 +28,7 @@ class Env;
class Arena;
struct FileDescriptor;
class GetContext;
class HistogramImpl;
class TableCache {
public:
@ -46,6 +47,7 @@ class TableCache {
const InternalKeyComparator& internal_comparator,
const FileDescriptor& file_fd,
TableReader** table_reader_ptr = nullptr,
HistogramImpl* file_read_hist = nullptr,
bool for_compaction = false, Arena* arena = nullptr);
// If a seek to internal key "k" in specified file finds an entry,
@ -54,7 +56,7 @@ class TableCache {
Status Get(const ReadOptions& options,
const InternalKeyComparator& internal_comparator,
const FileDescriptor& file_fd, const Slice& k,
GetContext* get_context);
GetContext* get_context, HistogramImpl* file_read_hist = nullptr);
// Evict any entry for the specified file number
static void Evict(Cache* cache, uint64_t file_number);
@ -63,7 +65,8 @@ class TableCache {
Status FindTable(const EnvOptions& toptions,
const InternalKeyComparator& internal_comparator,
const FileDescriptor& file_fd, Cache::Handle**,
const bool no_io = false, bool record_read_stats = true);
const bool no_io = false, bool record_read_stats = true,
HistogramImpl* file_read_hist = nullptr);
// Get TableReader from a cache handle.
TableReader* GetTableReaderFromHandle(Cache::Handle* handle);

52
db/version_set.cc
View file

@ -24,6 +24,7 @@
#include <string>
#include "db/filename.h"
#include "db/internal_stats.h"
#include "db/log_reader.h"
#include "db/log_writer.h"
#include "db/memtable.h"
@ -474,13 +475,18 @@ class LevelFileNumIterator : public Iterator {
class LevelFileIteratorState : public TwoLevelIteratorState {
public:
LevelFileIteratorState(TableCache* table_cache,
const ReadOptions& read_options, const EnvOptions& env_options,
const InternalKeyComparator& icomparator, bool for_compaction,
bool prefix_enabled)
: TwoLevelIteratorState(prefix_enabled),
table_cache_(table_cache), read_options_(read_options),
env_options_(env_options), icomparator_(icomparator),
for_compaction_(for_compaction) {}
const ReadOptions& read_options,
const EnvOptions& env_options,
const InternalKeyComparator& icomparator,
HistogramImpl* file_read_hist, bool for_compaction,
bool prefix_enabled)
: TwoLevelIteratorState(prefix_enabled),
table_cache_(table_cache),
read_options_(read_options),
env_options_(env_options),
icomparator_(icomparator),
file_read_hist_(file_read_hist),
for_compaction_(for_compaction) {}
Iterator* NewSecondaryIterator(const Slice& meta_handle) override {
if (meta_handle.size() != sizeof(FileDescriptor)) {
@ -491,7 +497,8 @@ class LevelFileIteratorState : public TwoLevelIteratorState {
reinterpret_cast<const FileDescriptor*>(meta_handle.data());
return table_cache_->NewIterator(
read_options_, env_options_, icomparator_, *fd,
nullptr /* don't need reference to table*/, for_compaction_);
nullptr /* don't need reference to table*/, file_read_hist_,
for_compaction_);
}
}
@ -504,6 +511,7 @@ class LevelFileIteratorState : public TwoLevelIteratorState {
const ReadOptions read_options_;
const EnvOptions& env_options_;
const InternalKeyComparator& icomparator_;
HistogramImpl* file_read_hist_;
bool for_compaction_;
};
@ -705,7 +713,7 @@ void Version::AddIterators(const ReadOptions& read_options,
const auto& file = storage_info_.LevelFilesBrief(0).files[i];
merge_iter_builder->AddIterator(cfd_->table_cache()->NewIterator(
read_options, soptions, cfd_->internal_comparator(), file.fd, nullptr,
false, arena));
cfd_->internal_stats()->GetFileReadHist(0), false, arena));
}
// For levels > 0, we can use a concatenating iterator that sequentially
@ -714,10 +722,12 @@ void Version::AddIterators(const ReadOptions& read_options,
for (int level = 1; level < storage_info_.num_non_empty_levels(); level++) {
if (storage_info_.LevelFilesBrief(level).num_files != 0) {
auto* mem = arena->AllocateAligned(sizeof(LevelFileIteratorState));
auto* state = new (mem) LevelFileIteratorState(
cfd_->table_cache(), read_options, soptions,
cfd_->internal_comparator(), false /* for_compaction */,
cfd_->ioptions()->prefix_extractor != nullptr);
auto* state = new (mem)
LevelFileIteratorState(cfd_->table_cache(), read_options, soptions,
cfd_->internal_comparator(),
cfd_->internal_stats()->GetFileReadHist(level),
false /* for_compaction */,
cfd_->ioptions()->prefix_extractor != nullptr);
mem = arena->AllocateAligned(sizeof(LevelFileNumIterator));
auto* first_level_iter = new (mem) LevelFileNumIterator(
cfd_->internal_comparator(), &storage_info_.LevelFilesBrief(level));
@ -810,8 +820,9 @@ void Version::Get(const ReadOptions& read_options,
user_comparator(), internal_comparator());
FdWithKeyRange* f = fp.GetNextFile();
while (f != nullptr) {
*status = table_cache_->Get(read_options, *internal_comparator(), f->fd,
ikey, &get_context);
*status = table_cache_->Get(
read_options, *internal_comparator(), f->fd, ikey, &get_context,
cfd_->internal_stats()->GetFileReadHist(fp.GetHitFileLevel()));
// TODO: examine the behavior for corrupted key
if (!status->ok()) {
return;
@ -3059,14 +3070,17 @@ Iterator* VersionSet::MakeInputIterator(Compaction* c) {
list[num++] = cfd->table_cache()->NewIterator(
read_options, env_options_compactions_,
cfd->internal_comparator(), flevel->files[i].fd, nullptr,
nullptr, /* no per level latency histogram*/
true /* for compaction */);
}
} else {
// Create concatenating iterator for the files from this level
list[num++] = NewTwoLevelIterator(new LevelFileIteratorState(
cfd->table_cache(), read_options, env_options_,
cfd->internal_comparator(), true /* for_compaction */,
false /* prefix enabled */),
list[num++] = NewTwoLevelIterator(
new LevelFileIteratorState(
cfd->table_cache(), read_options, env_options_,
cfd->internal_comparator(),
nullptr /* no per level latency histogram */,
true /* for_compaction */, false /* prefix enabled */),
new LevelFileNumIterator(cfd->internal_comparator(),
c->input_levels(which)));
}

17
util/file_reader_writer.cc
View file

@ -11,6 +11,7 @@
#include <algorithm>
#include "port/port.h"
#include "util/histogram.h"
#include "util/iostats_context_imp.h"
#include "util/random.h"
#include "util/rate_limiter.h"
@ -27,10 +28,18 @@ Status SequentialFileReader::Skip(uint64_t n) { return file_->Skip(n); }
Status RandomAccessFileReader::Read(uint64_t offset, size_t n, Slice* result,
char* scratch) const {
StopWatch sw(env_, stats_, hist_type_);
IOSTATS_TIMER_GUARD(read_nanos);
Status s = file_->Read(offset, n, result, scratch);
IOSTATS_ADD_IF_POSITIVE(bytes_read, result->size());
Status s;
uint64_t elapsed = 0;
{
StopWatch sw(env_, stats_, hist_type_,
(stats_ != nullptr) ? &elapsed : nullptr);
IOSTATS_TIMER_GUARD(read_nanos);
s = file_->Read(offset, n, result, scratch);
IOSTATS_ADD_IF_POSITIVE(bytes_read, result->size());
}
if (stats_ != nullptr && file_read_hist_ != nullptr) {
file_read_hist_->Add(elapsed);
}
return s;
}

8
util/file_reader_writer.h
View file

@ -12,6 +12,7 @@
namespace rocksdb {
class Statistics;
class HistogramImpl;
class SequentialFileReader {
private:
@ -33,16 +34,19 @@ class RandomAccessFileReader : public RandomAccessFile {
Env* env_;
Statistics* stats_;
uint32_t hist_type_;
HistogramImpl* file_read_hist_;
public:
explicit RandomAccessFileReader(std::unique_ptr<RandomAccessFile>&& raf,
Env* env = nullptr,
Statistics* stats = nullptr,
uint32_t hist_type = 0)
uint32_t hist_type = 0,
HistogramImpl* file_read_hist = nullptr)
: file_(std::move(raf)),
env_(env),
stats_(stats),
hist_type_(hist_type) {}
hist_type_(hist_type),
file_read_hist_(file_read_hist) {}
Status Read(uint64_t offset, size_t n, Slice* result, char* scratch) const;