From 5ea44519f3e51144861bc50f750c4d32c38b4b18 Mon Sep 17 00:00:00 2001
From: Florian Fischer <florian.fl.fischer@fau.de>
Date: Tue, 23 Mar 2021 14:31:27 +0100
Subject: [PATCH] [IO] make the behavior of the completer thread configurable
Available behaviors:
* none - the completer thread is not started
* schedule (default) - the completer thread will reap and schedule available
completions from worker IoContexts
* wakeup - the completer thread will wakeup all workers if it observes completions
in a worker IoContext. The Fiber produced by the completion will
be scheduled when the worker in which's IoContext the cqe lies
reaps its completions.
---
emper/Emper.hpp | 9 +++++++++
emper/Runtime.cpp | 10 +++++++---
emper/io/GlobalIoContext.cpp | 11 +++++++++--
meson.build | 10 ++++++++++
meson_options.txt | 7 +++++++
5 files changed, 42 insertions(+), 5 deletions(-)
diff --git a/emper/Emper.hpp b/emper/Emper.hpp
index 2138be46..2bfbf49f 100644
--- a/emper/Emper.hpp
+++ b/emper/Emper.hpp
@@ -97,4 +97,13 @@ static const bool IO_URING_SHARED_WQ =
false
#endif
;
+
+enum class IoCompleterBehavior {
+ schedule,
+ wakeup,
+ none,
+};
+
+static const enum IoCompleterBehavior IO_COMPLETER_BEHAVIOR =
+ IoCompleterBehavior::EMPER_IO_COMPLETER_BEHAVIOR;
} // namespace emper
diff --git a/emper/Runtime.cpp b/emper/Runtime.cpp
index 43ba9be7..e4b18974 100644
--- a/emper/Runtime.cpp
+++ b/emper/Runtime.cpp
@@ -92,7 +92,9 @@ Runtime::Runtime(workerid_t workerCount, RuntimeStrategyFactory& strategyFactory
// for each worker's IoContext one eventfd read is prepared before the
// globalCompleter is started and submits all previously prepared sqes.
globalIo = new GlobalIoContext(*this, workerCount);
- globalIo->startGlobalCompleter();
+ if constexpr (emper::IO_COMPLETER_BEHAVIOR != emper::IoCompleterBehavior::none) {
+ globalIo->startGlobalCompleter();
+ }
if constexpr (emper::STATS) {
globalIo->stats.workerId = -1;
@@ -196,8 +198,10 @@ auto Runtime::workerLoop(Worker* worker) -> void* {
if constexpr (emper::IO) {
auto* workerIo = new IoContext(*this);
- // submit the workers' CQ eventfds to the global IoContext
- globalIo->registerWorkerIo(*workerIo);
+ if constexpr (emper::IO_COMPLETER_BEHAVIOR != emper::IoCompleterBehavior::none) {
+ // submit the workers' CQ eventfds to the global IoContext
+ globalIo->registerWorkerIo(*workerIo);
+ }
// notify the globalCompleter that we have registered our eventfd
ioReadySem.notify();
diff --git a/emper/io/GlobalIoContext.cpp b/emper/io/GlobalIoContext.cpp
index 27b4b075..83799c78 100644
--- a/emper/io/GlobalIoContext.cpp
+++ b/emper/io/GlobalIoContext.cpp
@@ -14,6 +14,7 @@
#include "CallerEnvironment.hpp"
#include "Common.hpp"
+#include "Emper.hpp"
#include "Runtime.hpp"
#include "io/Future.hpp"
#include "io/IoContext.hpp"
@@ -82,7 +83,7 @@ auto GlobalIoContext::globalCompleterFunc(void* arg) -> void* {
// -> there are completions on this worker IoContext
switch (tag) {
// clang-11 does not support [[likely]] yet
- // TODO: remove the preprocessor check if clang ass [[likely]] support
+ // TODO: remove the preprocessor check if clang has [[likely]] support
#if defined __has_attribute
#if __has_attribute(likely)
[[likely]] // NOLINT(clang-diagnostic-unknown-attributes)
@@ -103,7 +104,13 @@ auto GlobalIoContext::globalCompleterFunc(void* arg) -> void* {
assert(submitted == 1);
- worker_io->reapAndScheduleCompletions<CallerEnvironment::ANYWHERE>();
+ if constexpr (emper::IO_COMPLETER_BEHAVIOR == emper::IoCompleterBehavior::wakeup) {
+ // Only wakeup sleeping workers and hope that the worker which
+ // has ready cqes will reap them soon.
+ globalIoContext->runtime.wakeupSleepingWorkers<CallerEnvironment::ANYWHERE>();
+ } else {
+ worker_io->reapAndScheduleCompletions<CallerEnvironment::ANYWHERE>();
+ }
}
break;
diff --git a/meson.build b/meson.build
index 9a6bca81..276a7c4e 100644
--- a/meson.build
+++ b/meson.build
@@ -93,6 +93,16 @@ endforeach
io_cq_lock_impl = get_option('io_cq_lock_implementation')
conf_data.set('EMPER_IO_CQ_LOCK_' + io_cq_lock_impl.to_upper(), true)
+io_completer_behavior = get_option('io_completer_behavior')
+if io_completer_behavior == 'maybe_wakeup'
+ if get_option('worker_sleep')
+ io_completer_behavior = 'wakeup'
+ else
+ io_completer_behavior = 'none'
+ endif
+endif
+conf_data.set('EMPER_IO_COMPLETER_BEHAVIOR', io_completer_behavior)
+
subdir('emper')
subdir('tests')
subdir('apps')
diff --git a/meson_options.txt b/meson_options.txt
index 06bd0206..ac1f842c 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -122,3 +122,10 @@ option(
choices: ['spin_lock', 'counting_try_lock', 'mutex'],
value: 'counting_try_lock',
)
+option(
+ 'io_completer_behavior',
+ type: 'combo',
+ description: 'The behaviour of the IO completer thread',
+ choices: ['schedule', 'maybe_wakeup'],
+ value: 'schedule',
+)
--
GitLab