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Exclude time waiting for rate limiter from rocksdb.sst.read.micros (#4102)

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Summary:
Our "rocksdb.sst.read.micros" stat includes time spent waiting for rate limiter. It probably only affects people rate limiting compaction reads, which is fairly rare.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4102

Differential Revision: D8848506

Pulled By: miasantreble

fbshipit-source-id: 01258ac5ae56e4eee372978cfc9143a6869f8bfc
This commit is contained in:
Zhongyi Xie 2018-07-13 18:29:50 -07:00 committed by Facebook Github Bot
parent 90fc40690a
commit 91d7c03cdc
2 changed files with 38 additions and 2 deletions
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9
util/file_reader_writer.cc
View File

@ -75,7 +75,8 @@ Status RandomAccessFileReader::Read(uint64_t offset, size_t n, Slice* result,
uint64_t elapsed = 0;
{
StopWatch sw(env_, stats_, hist_type_,
(stats_ != nullptr) ? &elapsed : nullptr);
(stats_ != nullptr) ? &elapsed : nullptr, true /*overwrite*/,
true /*delay_enabled*/);
IOSTATS_TIMER_GUARD(read_nanos);
if (use_direct_io()) {
#ifndef ROCKSDB_LITE
@ -117,9 +118,15 @@ Status RandomAccessFileReader::Read(uint64_t offset, size_t n, Slice* result,
while (pos < n) {
size_t allowed;
if (for_compaction_ && rate_limiter_ != nullptr) {
if (rate_limiter_->IsRateLimited(RateLimiter::OpType::kRead)) {
sw.DelayStart();
}
allowed = rate_limiter_->RequestToken(n - pos, 0 /* alignment */,
Env::IOPriority::IO_LOW, stats_,
RateLimiter::OpType::kRead);
if (rate_limiter_->IsRateLimited(RateLimiter::OpType::kRead)) {
sw.DelayStop();
}
} else {
allowed = n;
}

31
util/stop_watch.h
View File

@ -15,13 +15,17 @@ namespace rocksdb {
class StopWatch {
public:
StopWatch(Env* const env, Statistics* statistics, const uint32_t hist_type,
uint64_t* elapsed = nullptr, bool overwrite = true)
uint64_t* elapsed = nullptr, bool overwrite = true,
bool delay_enabled = false)
: env_(env),
statistics_(statistics),
hist_type_(hist_type),
elapsed_(elapsed),
overwrite_(overwrite),
stats_enabled_(statistics && statistics->HistEnabledForType(hist_type)),
delay_enabled_(delay_enabled),
total_delay_(0),
delay_start_time_(0),
start_time_((stats_enabled_ || elapsed != nullptr) ? env->NowMicros()
: 0) {}
@ -33,6 +37,9 @@ class StopWatch {
*elapsed_ += env_->NowMicros() - start_time_;
}
}
if (elapsed_ && delay_enabled_) {
*elapsed_ -= total_delay_;
}
if (stats_enabled_) {
statistics_->measureTime(hist_type_,
(elapsed_ != nullptr) ? *elapsed_ :
@ -40,6 +47,25 @@ class StopWatch {
}
}
void DelayStart() {
// if delay_start_time_ is not 0, it means we are already tracking delay,
// so delay_start_time_ should not be overwritten
if (elapsed_ && delay_enabled_ && delay_start_time_ == 0) {
delay_start_time_ = env_->NowMicros();
}
}
void DelayStop() {
if (elapsed_ && delay_enabled_ && delay_start_time_ != 0) {
total_delay_ += env_->NowMicros() - delay_start_time_;
}
// reset to 0 means currently no delay is being tracked, so two consecutive
// calls to DelayStop will not increase total_delay_
delay_start_time_ = 0;
}
uint64_t GetDelay() const { return delay_enabled_ ? total_delay_ : 0; }
uint64_t start_time() const { return start_time_; }
private:
@ -49,6 +75,9 @@ class StopWatch {
uint64_t* elapsed_;
bool overwrite_;
bool stats_enabled_;
bool delay_enabled_;
uint64_t total_delay_;
uint64_t delay_start_time_;
const uint64_t start_time_;
};