From b1663e74657d045e6f35b87bcea107e68767345f Mon Sep 17 00:00:00 2001
From: Craig Tiller <craig.tiller@gmail.com>
Date: Sun, 1 Feb 2015 22:09:38 -0800
Subject: [PATCH] Remove a major source of contention in thread_pool
- notify_one when new work is available to avoid thundering herd
problems
- checking conditions before entering cv_.wait() prevents a case that
these are not validated
---
src/cpp/server/thread_pool.cc | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/src/cpp/server/thread_pool.cc b/src/cpp/server/thread_pool.cc
index a46d4c64d2..35d61244f2 100644
--- a/src/cpp/server/thread_pool.cc
+++ b/src/cpp/server/thread_pool.cc
@@ -41,7 +41,8 @@ ThreadPool::ThreadPool(int num_threads) {
for (;;) {
std::unique_lock<std::mutex> lock(mu_);
// Wait until work is available or we are shutting down.
- cv_.wait(lock, [=]() { return shutdown_ || !callbacks_.empty(); });
+ if (!shutdown_ || callbacks_.empty())
+ cv_.wait(lock, [=]() { return shutdown_ || !callbacks_.empty(); });
// Drain callbacks before considering shutdown to ensure all work
// gets completed.
if (!callbacks_.empty()) {
@@ -71,7 +72,7 @@ ThreadPool::~ThreadPool() {
void ThreadPool::ScheduleCallback(const std::function<void()> &callback) {
std::lock_guard<std::mutex> lock(mu_);
callbacks_.push(callback);
- cv_.notify_all();
+ cv_.notify_one();
}
} // namespace grpc
--
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