From 6560692c670bcf34fc922474bf37f3c18b8768af Mon Sep 17 00:00:00 2001 From: Rasmus Munk Larsen Date: Fri, 22 Feb 2019 13:56:26 -0800 Subject: Improve EventCount used by the non-blocking threadpool. The current algorithm requires threads to commit/cancel waiting in order they called Prewait. Spinning caused by that serialization can consume lots of CPU time on some workloads. Restructure the algorithm to not require that serialization and remove spin waits from Commit/CancelWait. Note: this reduces max number of threads from 2^16 to 2^14 to leave more space for ABA counter (which is now 22 bits). Implementation details are explained in comments. --- unsupported/test/cxx11_eventcount.cpp | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'unsupported/test/cxx11_eventcount.cpp') diff --git a/unsupported/test/cxx11_eventcount.cpp b/unsupported/test/cxx11_eventcount.cpp index 2f1418684..3ca8598c7 100644 --- a/unsupported/test/cxx11_eventcount.cpp +++ b/unsupported/test/cxx11_eventcount.cpp @@ -30,11 +30,11 @@ static void test_basic_eventcount() EventCount ec(waiters); EventCount::Waiter& w = waiters[0]; ec.Notify(false); - ec.Prewait(&w); + VERIFY(ec.Prewait()); ec.Notify(true); ec.CommitWait(&w); - ec.Prewait(&w); - ec.CancelWait(&w); + VERIFY(ec.Prewait()); + ec.CancelWait(); } // Fake bounded counter-based queue. @@ -112,7 +112,7 @@ static void test_stress_eventcount() unsigned idx = rand_reentrant(&rnd) % kQueues; if (queues[idx].Pop()) continue; j--; - ec.Prewait(&w); + if (!ec.Prewait()) continue; bool empty = true; for (int q = 0; q < kQueues; q++) { if (!queues[q].Empty()) { @@ -121,7 +121,7 @@ static void test_stress_eventcount() } } if (!empty) { - ec.CancelWait(&w); + ec.CancelWait(); continue; } ec.CommitWait(&w); -- cgit v1.2.3