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Relax memory order for faster tickers

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Summary:
The default behavior for atomic operations is sequentially consistent ordering
which is not needed for simple counters (see:
http://en.cppreference.com/w/cpp/atomic/memory_order). Change the memory order
to std::memory_order_relaxed for better performance.

Test Plan: make clean all check

Reviewers: rven, anthony, yhchiang, aekmekji, sdong, MarkCallaghan, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D46953
This commit is contained in:
Andres Noetzli 2015-09-15 10:52:00 -07:00
parent 4886073174
commit df22e2fb71
1 changed files with 2 additions and 2 deletions
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4
util/statistics.cc
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@ -62,7 +62,7 @@ void StatisticsImpl::setTickerCount(uint32_t tickerType, uint64_t count) {
tickerType < INTERNAL_TICKER_ENUM_MAX :
tickerType < TICKER_ENUM_MAX);
if (tickerType < TICKER_ENUM_MAX || enable_internal_stats_) {
tickers_[tickerType].value = count;
tickers_[tickerType].value.store(count, std::memory_order_relaxed);
}
if (stats_ && tickerType < TICKER_ENUM_MAX) {
stats_->setTickerCount(tickerType, count);
@ -75,7 +75,7 @@ void StatisticsImpl::recordTick(uint32_t tickerType, uint64_t count) {
tickerType < INTERNAL_TICKER_ENUM_MAX :
tickerType < TICKER_ENUM_MAX);
if (tickerType < TICKER_ENUM_MAX || enable_internal_stats_) {
tickers_[tickerType].value += count;
tickers_[tickerType].value.fetch_add(count, std::memory_order_relaxed);
}
if (stats_ && tickerType < TICKER_ENUM_MAX) {
stats_->recordTick(tickerType, count);